source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-4944 | nomenclature, ionic-compounds, history-of-chemistry
Title: How did Halogens become known as Halogens? They are not the only elements that form salts! Having never given it a though before, I recently discovered (in a different context) that the prefix halo- actually means 'salt' or 'sea' and the suffix -gen means 'to form' or 'to generate'. So the Halogens are the elements that 'form salts'. But there are salts that do not have halogens in them, like $\ce{Na2S}$ or $\ce{(NH4)2SO4}$. Was it known at the time that other salts existed, and what other names for this group might have been considered?
On a side note, why aren't Group I metals called halogens? Doesn't it take two to tango (I mean, to form salts?) This seems like a bit of a rhetorical question, so this isn't a terribly formal or authoritative answer, but anyhow - a lot of chemical nomenclature is like lava flow. It solidified and people just worked around it.
The halogens are so named because they have a rich chemistry of ionic compounds (fluorine through iodine, anyhow). However, both the halogens and the group I metals can form a wide range of things that aren't salts. The noble gases can form compounds with elements of low birth. The rare earth elements aren't particularly rare. Oxygen ('acid-former') is not a necessary component of acids. Technetium ('artificial' + ium) is produced in nature in significant quantities.
In addition, a lot of chemistry defies our human efforts to succintly categorise things, so at some point chemists have tried their best to find pragmatic general descriptors that unite groups of elements or molecules on the basis of the properties or constitution. The divide between organic and inorganic chemistry and the resulting exceptions and edge cases in classification (such as mellitic anhydride) is a good example of this. The map is not the territory.
The following is multiple choice question (with options) to answer.
Compounds that form from two or more nonmetallic elements are called what? | [
"hydrogen bonds",
"ionic bonds",
"valent bonds",
"covalent bonds"
] | D | Compounds that form from two or more nonmetallic elements, such as carbon and hydrogen, are called covalent compounds . In a covalent compound, atoms of the different elements are held together in molecules by covalent bonds. These are chemical bonds in which atoms share valence electrons. The force of attraction between the shared electrons and the positive nuclei of both atoms holds the atoms together in the molecule. A molecule is the smallest particle of a covalent compound that still has the properties of the compound. |
SciQ | SciQ-4945 | palaeontology, herpetology
Title: How big can cold-blooded animals get? It seems impossible to have reptiles the size of dinosaurs, just because they are really big! Did they have different systems of maintaining body temperature or maybe they weren't the exact type of animals that we today call reptiles? Answer is quite simple as from @Alan Boyd link. They are cold blooded and thus, can go out for hunt in cold, they need to stay put till they get some prey.
So, it mainly depend on the temperature of the outside, I found this interesting paper on relation of body sizes and latitude.
Body sizes of poikilotherm vertebrates at different latitudes
Maximum sizes of 12,503 species of poikilotherm vertebrates were
analyzed for latitudinal trends, using published data from 75 faunal
studies. A general trend appears which may be summarized by the rule
"among fish and amphibian faunas the proportion of species with large
adult size tends to increase from the equator towards the poles". The
rule holds for freshwater fish, deepsea fish, anurans, urodeles, and
marine neritic fish arranged roughly in order of decreasing clarity of
the trend). In general the rule applies not only within these groups
of families but also within single families. In reptile groups, the
rule holds weakly among snakes and not at all among lizards or
non-marine turtles. Possible explanations include an association
between small size and greater specialization in the tropics; the
possibility in poikilo-therms of heat conservation or of some other
physiological process related to surface/volume ratio; selection for
larger size in regions subject to winter food shortages; and an
association between large adult size and high reproductive potential
in cold regions. Other suggestions can be advanced, but all are
conjectural and few are subject to test. Global size - latitude trends
should be looked for in other living groups.
Cite: Lindsey, C. C., 1966: Body sizes of poikilotherm vertebrates at
different latitudes. Evolution: 456-465
Now lets compare some of the largest cold blooded Animals:
Reptiles
Amphibians
Fishes (Pisces)
The following is multiple choice question (with options) to answer.
The ability to maintain a stable internal temperature, despite the climate, is exhibited by members of what animal group? | [
"reptiles",
"fish",
"mammals",
"parasites"
] | C | Not really. Like all mammals, polar bears maintain a stable internal temperature. They do not need to stay warm by lying in the sun. This allows them to live in cold climates. |
SciQ | SciQ-4946 | acid-base, equilibrium, ph, electronic-configuration
Covalent compounds of elements in the third period and below tend to be very weak bases, if at all. I'm not sure why, but I suspect that it's because bonds involving these elements tend to form much weaker dipoles than bonds involving nitrogen. The weaker dipole would limit their ability to forcibly pull protons off of water molecules.
All that said, there are many ionic compounds that form basic solutions due to containing the cation of a weak acid. In these cases the base is a cation, not a molecule. Certainly some of these cations contain nitrogen, but many do not. Examples without nitrogen include any soluble carbonates and bicarbonates and any salts of carboxylic acids.
The following is multiple choice question (with options) to answer.
What are substances that provide hydrogen ions (h+) and lower ph? | [
"acids",
"bases",
"nutrients",
"proteins"
] | A | Acids are substances that provide hydrogen ions (H+) and lower pH, whereas bases provide hydroxide ions (OH–) and raise pH. The stronger the acid, the more readily it donates H+. For example, hydrochloric acid and lemon juice are very acidic and readily give up H+ when added to water. Conversely, bases are those substances that readily donate OH–. The OH– ions combine with H+ to produce water, which raises a substance’s pH. Sodium hydroxide and many household cleaners are very alkaline and give up OH– rapidly when placed in water, thereby raising the pH. Most cells in our bodies operate within a very narrow window of the pH scale, typically ranging only from 7.2 to 7.6. If the pH of the body is outside of this range, the respiratory system malfunctions, as do other organs in the body. Cells no longer function properly, and proteins will break down. Deviation outside of the pH range can induce coma or even cause death. So how is it that we can ingest or inhale acidic or basic substances and not die? Buffers are the key. Buffers readily absorb excess H+ or OH–, keeping the pH of the body carefully maintained in the aforementioned narrow range. Carbon dioxide is part of a prominent buffer system in the human body; it keeps the pH within the proper range. This buffer system involves carbonic acid (H2CO3) and bicarbonate (HCO3–) anion. If too much H+ enters the body, bicarbonate will combine with the H+ to create carbonic acid and limit the decrease in pH. Likewise, if too much OH– is introduced into the system, carbonic acid will rapidly dissociate into bicarbonate and H+ ions. The H+ ions can combine with the OH– ions, limiting the increase in pH. While carbonic acid is an important product in this reaction, its presence is fleeting because the carbonic acid is released from the body as carbon dioxide gas each time we breathe. Without this buffer system, the pH in our bodies would fluctuate too much and we would fail to survive. |
SciQ | SciQ-4947 | thermodynamics, fluid-dynamics, pressure
Title: Variable area manometer duct How does one measure the pressure at the end of the manometer tube when the manometer tube itself is having a variable area? The area of the manometer tube makes no difference. All that matters is the difference in the heights of the two ends (labelled $x$ in your diagram). That's why pressure units like the torr exist that are (or rather were) defined as the pressure difference when the difference in height of a mercury manometer is 1mm. All that matters is the height difference.
The following is multiple choice question (with options) to answer.
What are mercury manometers often used to measure? | [
"balance",
"blood pressure",
"weight",
"brain waves"
] | B | Mercury manometers are often used to measure arterial blood pressure. An inflatable cuff is placed on the upper arm as shown in Figure 11.17. By squeezing the bulb, the person making the measurement exerts pressure, which is transmitted undiminished. |
SciQ | SciQ-4948 | homework-and-exercises, rocket-science, estimation, satellites, propulsion
Title: Launch small satellite? I want to build a small satilite and launch it into low space orbit. Nothing 'too fancy' a Raspberry Pi to power the systems, camera which'all transmit video and also a radio reviver and transmitter, maybe a small power bank to power the Pi and solar panels to charge that and gyro for stability in space instead of multiple thrusters. Hopefully it should last a few weeks before it burns up. The weight of the satilite would be under 5Kg. Also would radiation cause any short term harm to the electronics?
I was also thinking if I could first launch it with a weather balloon, have a small chemical rocket fire just before the weather balloon pops and then once it's reached micro gravity the rocket falls away and a canister of compressed air can accelerate it from there to a distance where should last a couple weeks.
I was also thinking about ion thrusters but they use a lot of electricity
Would this be possible at all? @antlersoft is right. You'd still need a powerful rocket to get moving fast enough to enter into orbit around the Earth, so probably not, unless it's a really really big balloon holding a really big rocket!
The term "microgravity" might be a bit misleading. The gravity up there is almost as strong as it is on the surface. The key is to go fast enough so that your "fall" towards earth actually ends up being an orbit. That's about 7.7 kilometers per second!!
If you are inside a spacecraft, in an orbit, moving at such an orbital velocity, you would also be in orbit around the earth. If you just look at how your body moves with respect to the spacecraft, you could call it "microgravity" (lots of people do, even astronauts) but maybe it should be called micro-acceleration with respect to the spacecraft.
The following is multiple choice question (with options) to answer.
What did rockets help launch into space during their beginning? | [
"shuttles",
"satellites",
"rovers",
"sensors"
] | B | One of the first uses of rockets in space was to launch satellites. A satellite is an object that orbits a larger object. An orbit is a circular or elliptical path around an object. Natural objects in orbit are called natural satellites. The Moon is a natural satellite. Human-made objects in orbit are called artificial satellites. |
SciQ | SciQ-4949 | acoustics, air, displacement
\end{align}$$
That is a Very Loud Pop - about 80 dB. Even if we argue that only a small fraction of this pressure ends up in the audible range there is no doubt in my mind you would hear "something".
So yes, you can hear that parchment disappearing. No problem. Even if some of my approximations are off by a factor 10 or greater. We have about 5 orders of magnitude spare.
AFTERTHOUGHT
If you have ever played with a "naked" loudspeaker (I mean outside of the enclosure, so something like this one from greatplainsaudio.com):
The following is multiple choice question (with options) to answer.
What sound can be heard when sound waves bounce back from a hard object? | [
"eerie",
"boom",
"echo",
"loop"
] | C | Did you ever hear an echo of your own voice? An echo occurs when sound waves bounce back from a hard object. The man in Figure below is trying to create an echo by shouting toward a rock wall. When the sound waves strike the rock wall, they can’t pass through. Instead, they bounce back toward the man, and he hears an echo of his voice. An echo is just one example of how waves interact with matter. |
SciQ | SciQ-4950 | biochemistry, cell-biology, dna-replication, thermodynamics
RNA first (aka The RNA World Hypothesis)
Some theories suggest RNA came before functional proteins. In fact, this has been the de facto theory, because we had no mechanism to explain how proteins could self-replicate - something that has recently been demonstrated. In addition, this follows the central dogma, and would explain not only the development protein synthesis but also genetic information storage (the latter of which cannot be directly explained by the protein-first theory alone).
An idea behind this is that some RNA was able to auto-synthesize the first RNA-replicating enzymes. This sounds like a catch-22, but this study had found some RNA strands when joined can self-create an enzyme that replicates itself - the literal chemical makeup of this enzyme are RNA-oligonucleotides.
However, these RNA fragments in the lab have been take from existing ribozymes, so they may not be an accurate indicator for the first, spontaneously-created enzymes.
Limitations from and only RNA-first model stem from the fact that currently RNA synthesis/replication processes are detailed, intricate, and fragile. The chances of spontaneous reactions alone creating this process seem minuscule (though as mentioned earlier life took a LONG time to develop).
Until recently, another cited limitation concerned the fact that no known organisms replicate RNA. However, some viruses manage to code for RNA-replicated proteins, and (as mentioned earlier) RNA’s capability of self-replication has been recently discovered, be it in a lab setting.
Other theories
The last main debated theory concerns metabolism. This idea suggests metabolic processes occurred before the first life form, since many metabolic processes known today synthesize amino acids and nucleic acids from chemicals in our diet (how our body make the building blocks).
However, such a huge part of what makes metabolism today possible is driven by enzymes, which are proteins. Because of this, all of these processes would have to be dramatically slowed down in rate to mimic spontaneous reactions in primordial conditions, and on top of that there would have to be an explanation for how energetically unfavorable reactions in metabolism would occur. Most of these energetically unfavorable reactions in current metabolism harvest the potential energy in ATP, which longhand is adenosine triphosphate. The molecule adenosine is also used as one of the bases in nucleic acids, which at some level inherently contributes towards to the RNA World Hypothesis.
The following is multiple choice question (with options) to answer.
Robert merrifield developed the first synthetic approach for making what essential cell substances in the lab? | [
"proteins",
"cells",
"acids",
"lipids"
] | A | Cells in our bodies have an intricate mechanism for the manufacture of proteins. Humans have to use other techniques in order to synthesize the same proteins in a lab. The chemistry of peptide synthesis is complicated. Both active groups on an amino acid can react and the amino acid sequence must be a specific one in order for the protein to function. Robert Merrifield developed the first synthetic approach for making proteins in the lab, a manual approach which was lengthy and tedious (and, he won the Nobel Prize in Chemistry in 1984 for his work). Today however, automated systems can crank out a peptide in a very short period of time. |
SciQ | SciQ-4951 | quarks, elementary-particles
Title: Upness and downness There is a flavour for almost any type of quark [from here]:
isospin: $I_3=\frac{1}{2}((n_u-n_{\bar{u}})-(n_d-n_{\bar{d}}))$
strangeness: $S = −(n_s − n_{\bar s})$
charmness: $C = (n_c − n_{\bar c})$
bottomness: $B′ = −(n_b − n_{\bar b})$
topness: $T = (n_t − n_{\bar t})$
(where $n_i$ is the number of quarks $i$, and $\bar i$ is anti-$i$)
Why are the up and down quarks in this sense special, that they do not give rise to a upness nor downness, but rather to isospin. Consider a hadron with only up and down quarks. Given its isospin
$$I_3=\frac{1}{2}\left((n_u-n_\bar{u})-(n_d-n_\bar{d})\right)$$
and its charge
$$Q=I_3=\frac{2}{3}(n_u-n_\bar{u}) - \frac{1}{3}(n_d - n_\bar{d})$$
we can know what you called upness and downness, i.e. $n_u-n_\bar{u}$, and $n_d-n_\bar{d}$, respectively, modulo a sign perhaps. Then, as often, habits inherited from historical development will not change because the improvement would be perceived as too small to be worth it.
The following is multiple choice question (with options) to answer.
Strangeness, charm, bottomness, and topness are properties of what subatomic particle? | [
"pion",
"dark matter",
"quarks",
"molecules"
] | C | ± symbols are the values for antiquarks. B is baryon number, S is strangeness, c is charm, b is bottomness, t is topness. Values are approximate, are not directly observable, and vary with model. |
SciQ | SciQ-4952 | fluid-dynamics, pressure, fluid-statics, thought-experiment
at a local level, the random motion of particles is the cause of pressure,
Random motion of particles is measured by temperature; the higher the temperature, the more intense the random motion.
If we are to talk about causes, the cause of pressure on some wall is first and foremost mutual interaction of the particles and the wall. The fact that the particles move randomly is secondary. True, in gases increase of pressure often goes with increase in this random motion, because the increase of gas pressure can be done only by putting in substantial energy. But in liquids, it is possible to increase the pressure substantially with negligible amount of work and so with negligible change in intensity of this random motion.
Pressure of such liquid is due to force interaction of the particles with walls and each other, not necessarily due to their random motion. It suffices that particles push or pull each other. They do not have to move rapidly. You can have high pressure in very cold water or in ice cold at 1 K.
When pressure of a liquid water is increased, say, by moving a piston in a blocked syringe filled with water, water temperature increase is very small and is usually neglected.
Now to your question - gravity isn't necessary for pressure either. What is necessary to increase pressure is some other body that will squeeze the gas or liquid into smaller volume. On Earth, this body is the Earth with its gravity, but the same pressure is achieved in a closed vessel, such as the International Space Station, simply by making it robust enough to withstand the pressure and pushing in enough amount of gas. There is no effective gravity there, but there is pressure close to 100kPa, due to walls not allowing the gas to escape.
The following is multiple choice question (with options) to answer.
What needs to happen to temperature to cause pressure to increase dramatically? | [
"small increase",
"boiling point",
"no increase",
"large increase"
] | D | The pressure increases dramatically due to large increase in temperature. |
SciQ | SciQ-4953 | genetics, evolution, human-evolution, retrovirus
Title: Endogenous retroviral insertions as evidence for evolutionary relationships among primates A synopsis of a 2005 paper in PlosBiology by Yohn et al. states that:
Searching the genomes of a subset of apes and monkeys revealed that
the retrovirus had integrated into the germline of African great apes
and Old World monkeys—but did not infect humans and Asian apes
(orangutan, siamang, and gibbon). This undermines the notion that an
ancient infection invaded an ancestral primate lineage, since great
apes (including humans) share a common ancestor with Old World
monkeys.
Also, Micheal Lynch writes :
"Remarkably, we have found many cases of parallel intron gains at
essentially the same sites in independent genotypes," Lynch said.
"This strongly argues against the common assumption that when two
species share introns at the same site, it is always due to
inheritance from a common ancestor."
Since shared ERVs in humans and chimps is touted as one of the proofs of humans and chimps sharing ancestry (like by Ken Miller here), does the above paper (and quote) undermine this line of reasoning?
Is there any good (recent) source which discusses proof of common descent using ERVs? The Yohn et. al. (2005) paper (from Evan Eichler's lab) is describing a single type of endogenous retroviral element (loosely think of it as a 'species'), called PTERV1. They show that there were multiple independent infection events that resulted in permanent integrations in the ancestors of modern species (~3-4 MYA in the ancestors of gorillas and chimps, ~1.5 MYA in the ancestors of baboons and macaques). This in no way contradicts the notion of common ancestors among the apes/monkeys; indeed, they state this as a given in their analysis (emphasis mine):
A total of 275 of the insertion sites mapped unambiguously to
non-orthologous locations (Table 2), indicating that the vast majority
of elements were lineage-specific (i.e., they emerged after the
divergence of gorilla/chimpanzee and macaque/baboon from their common
ancestor).
The following is multiple choice question (with options) to answer.
Australopithecus afarensis is an ancestor of what primate? | [
"orangutans",
"lemurs",
"humans",
"gorillas"
] | C | Australopithecus afarensis is a human ancestor that lived about 3 million years ago. |
SciQ | SciQ-4954 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
Organs that produce eggs and secrete estrogen are part of what system? | [
"female reproductive system",
"circulatory system",
"digestive system",
"male reproductive system"
] | A | one of two female reproductive organs that produces eggs and secretes estrogen. |
SciQ | SciQ-4955 | earth-history
Common elements in space, such as CO2, H20, CH4 and NH3 are gaseous at Earth's distance from the sun and as a result, are unlikely to stick to anything in the Earth's formation region. This is true for all 4 inner planets and likely all rocky worlds. Rocky planets likely can only form close to their star, just as gas giants, ice giants or other icy abundant bodies like comets and low-density moons, can only form further out.
Gases like the 4 above can begin to be retained around a planet after it reaches a sufficiently large mass with low enough surface temperature to retain those gases by gravity.
The boundaries where CO2, H20, CH4, NH3 and other gases can be found in the protoplanetary disk is called the frost line. Different gases have different frost lines depending on their freezing point.
It's thought that much of Earth's water, CO2, CH4 and NH3 came to the Earth by comet after the planet formed. There's still some uncertainty on the percentages, as some of those elements could have been trapped during formation.
Just to add, hydrogen and helium are obviously abundant, but will only begin to accrue around a planet of a certain mass. In our solar-system, only Jupiter and Saturn are massive enough to accrue hydrogen and helium. That's why Uranus and Neptune are relatively low on hydrogen and helium compared to the universal abundance.
Argon is in Earth's atmosphere because it forms from gradual radioactive decay of Potassium-40. Earth's Helium is also present as a result of radioactive decay.
The following is multiple choice question (with options) to answer.
What are the most common types of compounds found on earth? | [
"ionic compounds",
"hydrogen-based compounds",
"carbon-based compounds",
"sodium - based compounds"
] | C | Cellulose is a compound found in plants. The chief component of cellulose is carbon. Cellulose is one of many carbon-based compounds that make up living things. In fact, carbon-based compounds are the most common type of compound on Earth. More than 90 percent of all known compounds contain carbon. Do you know why carbon is found in so many compounds? Read on to find out. |
SciQ | SciQ-4956 | homework-and-exercises, newtonian-mechanics, newtonian-gravity, orbital-motion
Title: Kepler's law problem
Two planets A and B move around the Sun in elliptic orbits with time periods $T_A$ and
$T_B$ respectively. If the eccentricity of the orbit of B is ε and its distance of closest
approach to the Sun is R, then the maximum possible distance between the planets is?
Attempt at a solution
I think i am almost there but this is what i have so far.
Using the eccentricity and R, I found the expression for the semi major axis of B as $R_{SB}$=$\frac{R}{1-\epsilon}$ and using the relation for time periods, i have the expression for $R_{SA}$=$[\frac{T_A}{T_B}]^{2/3}$$\frac{R}{1-\epsilon}$
Now my doubt is whether to assume that two planets have sun at the same focus(say, on the right side ...picture concentric ellipses) in which case the maximum distance is when one of them is closest to the sun and the other is farthest OR if the two planets have sun at different focii (one to the left and other to the right, in this the orbits overlap partly; in either of the case, i cannot find a perfect expression for the maximum distance!
These are the two cases i am picturing, of course there might be many more oriented differently in the 2D. In the diagram on the left, max distance is when both are at their apogee. In the diagram on the left, its when one is at the apogee and the other is at the perigee. Is it possible to find an expression for distance which i can differentiate to find the max value?
Answer is $\frac{1+\epsilon}{1-\epsilon}$(1+($\frac{T_A}{T_B})^\frac{2}{3})$R Make a sketch of the possible relative orientations of the 2 orbits. The planets will have maximum separation if the orbits are oriented with major axes aligned but set at $180^{\circ}$ - ie apogees on opposite sides of the focus.
The following is multiple choice question (with options) to answer.
Which planet is closest to the sun? | [
"Jupiter",
"Venus",
"Earth",
"mercury"
] | D | The four planets closest to the Sun - Mercury, Venus, Earth, and Mars - are the inner planets . They are similar to Earth. All are solid, dense, and rocky. None of the inner planets has rings. Compared to the outer planets, the inner planets are small. They have shorter orbits around the Sun and they spin more slowly. Venus spins backwards and spins the slowest of all the planets. |
SciQ | SciQ-4957 | reproduction, asexual-reproduction
Title: can self-fertilization in flowers be called asexual reproduction? Suppose a flower having both male and female reproductive parts is self-fertilized then can this be called asexual reproduction...?I'm quite confused cause in this case the fusion of male and female gametes do take place but again the gametes are from the same parent....please help. According to this article from Berkeley, asexual reproduction is:
Any reproductive process that does not involve meiosis or syngamy
Using this definition of asexual reproduction and knowing self-fertilization involves meiosis and syngamy, it is not asexual.
The following is multiple choice question (with options) to answer.
What do you call it when adult fish of the same species come together in a group and release gametes into the water at the same time? | [
"migration",
"spawning",
"schoaling",
"poaching"
] | B | Nearly all fish reproduce sexually and have separate sexes. Fertilization is generally external, and most fish are oviparous. Many adults of the same species may come together in a group and release gametes into the water at the same time, which is called spawning. Fish hatch into larvae that are different from the adult form of the species. |
SciQ | SciQ-4958 | thermodynamics, heat, ideal-gas
Title: Combined gas law in an open atmosphere The question was asked about pressure vs. Volume increasing in an ideal gas as temperature is increased. My question then is this. What is the formula to determine how much volume and pressure will increase as temperature is increased?
Let me frame the question this way. PV/T=P2V2/T2 this formula works for a controlled system where more than one of these values can be maintained. If we apply a known amount of heat, say n, to the atmosphere, what formula would be used to calculate volume and pressure as the temperature is increased? Technically speaking, If you managed to create a planet with an ideal gas atmosphere, the atmosphere would just float away. Why?
One of the approximations of an ideal gas is
There are no attractive or repulsive forces between the molecules or the surroundings
This means that the gas wouldn't feel the force of gravity!
So if I had a jar of ideal gas, the pressure wouldn't increase as I went to a greater depth in the jar(It does increase in gasses too, just like it does in liquids).
I know this sounds strange but all it really means is that you cannot apply the ideal gas approximation to a system the size of our atmosphere. This approximation works well for small systems(A jar of ideal gas), because the effects of gravity are pretty negligible.
So to analyse effects of change in temperature on the whole atmosphere, you'll need a better model. Maybe considering the atmosphere a non-viscous fluid can help, I don't know. You should research on this.
Note that other approximations like the Van der Waals equation wouldn't help too because they too neglect the effect of gravity.
The following is multiple choice question (with options) to answer.
What happens to the volume of a gas as the kelvin temperature increases? | [
"it drops",
"it decreases",
"it increases",
"it continues"
] | C | The volume of a gas increases as the Kelvin temperature increases. |
SciQ | SciQ-4959 | orbitals, atoms, spin
Once you have all the term symbols you can then apply selection rules to see which transitions are allowed.
Finally if the configuration contains, say, p$^2$ then one has also to consider the Pauli principle and it is more tricky. The way to do this is to list all s1, s2, l1, l2 values and remove any with the same set of quantum numbers. Finally when you have the term symbol Hund's rules are used to determine which levels and states are lowest in energy. (Many text books work through the p$^2$ case, See for example Steinfeld, 'Molecules & radiation')
The following is multiple choice question (with options) to answer.
If only one atom of a specific type is present what is not used? | [
"covalent bond",
"subscript",
"consonant",
"subset"
] | B | If only one atom of a specific type is present, no subscript is used. |
SciQ | SciQ-4960 | evolution, herpetology, dinosaurs
Title: Evolution of dinosaurs What did dinosaurs evolve from? Was it the reptiles that evolved from amphibians? I have been researching this but am very confused with who their direct predecessor was. Amphibians evolved from fish...reptiles from amphibians...dinosaurs from reptiles (?)...and birds from dinosaurs. That is my understanding, but it could be wrong. How are dinosaurs related to reptiles? And if they did evolve from reptiles, which kind of reptiles (such as lizards, crocodiles, or turtles for example)? Source of information
See the post The best free and most up to date phylogenetic tree on the internet? for info about how to find such information.
Generally speaking, you might be interested in an intro to phylogenetics such as the one provided in this answer for example.
Where are dinosaurs in the tree of life?
Dinosaurs fall within the Reptiliomorpha clade. Please note that Reptiliomorpha does not quite correspond to what we today call reptiles. Please see the post If dinosaurs could have feathers, would they still be reptiles?
Reptiliomorpha is the sister clade to Amphibia (from here) which contain all living amphibians.
If you look within the Amniota, you will find all of the following
Here, you see that turtles and mammals are an off-shoot of Diapsida. So dinosaurs are not mammals and there are not closely related to turtles. Now if you click on Diapsida you will find ...
the Archosauromorpha which contains all crocodiles, birds and dinosaurs. You can keep going to find Therapoda which contains many dinosaurs and birds. You can keep going like this for yourself and discover the entire tree of life!
Reacting to your sentences
What did dinosaurs evolve from?
When asking this question, please do not forget that no species evolved from an extant species. If this is unclear to you, you should have a look at this post.
Was it the reptiles that evolved from amphibians?
Well... the term reptile is a mess because it does not represent a monophyletic group (see this post). If you do not understand the term monophyletic, then you should have a look at this answer.
Amphibians evolved from fish...
The following is multiple choice question (with options) to answer.
What are the earliest reptile genus named? | [
"hylonomus",
"brachyophis",
"scolecophis",
"collorhabdium"
] | A | Earliest Reptile: Hylonomus . The earliest known reptile is given the genus name Hylonomus . It was about 20 to 30 centimeters (8 to 12 inches) long, lived in swamps, and ate insects and other small invertebrates. |
SciQ | SciQ-4961 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
What produces all the cells of the root and the root cap? | [
"interior meristem",
"apical meristem",
"somatic meristem",
"algal meristem"
] | B | |
SciQ | SciQ-4962 | human-biology, endocrinology, organs
Title: Is there a blood panel lab test that measures all the hormone-producing glands? I understand that there are gland-specific hormone tests, such as:
Secretin: for the pancreas; and
Prolactin/ACTH: for the pituitary; and
PTH: for the payathyroid, etc.
However, are there any "composite" blood panels that test the "entire gamut/spectrum" of organs/glands, similar to what composite metabolic panels do for your cell counts? There are no composite tests that measure all the clinically important hormone producing glands. There are too many hormones produced by too many hormone producing cells/tissues in the body to test for all of them all at once (i.e. in a panel).
For illustrative purposes only... if you go to wikipedia they have a list of all hormones in the human body which is definitely far from complete! But it gives you an indication of just "how many" hormones there are and why testing for all of them is impossible in a panel.
Even with regard only to pancreatic hormones, there are several hormones produced (e.g. insulin, glucagon, somatostatin) that aren't necessarily a marker of the glands overall function (because they are not necessarily involved in the same function). Each of these hormones has different functions even though they are produced by the same gland.
Regardless, from a medical perspective you would never have a reason to test for all of them anyway. If you tested enough of them you'd find at least one of them that would - by chance - be abnormal.
Additionally, if you asked a handful of scientists to name fifty hormones there would be a lot of different hormones on each of their lists. The definition of hormone is vague, and we are learning more about new hormones every day. In the last decade we have learned that bile acids - chemicals predominately produced by the liver that are involved in dietary fat absorption - also act as hormones. There aren't clinical reasons to study all of these molecules just yet, but this demonstrates that it would be impossible to measure all of them all at the same time in one particular "panel".
The following is multiple choice question (with options) to answer.
What is the master gland of the endocrine system? | [
"Hypothyroid",
"Thyroid",
"pituitary gland",
"Thymus"
] | C | The hypothalamus is part of the brain and also secretes hormones, thus connecting the nervous and endocrine systems. The pituitary gland is the master gland of the endocrine system and controls other endocrine glands. Endocrine glands also include the thyroid gland, adrenal glands, pancreas, and gonads. |
SciQ | SciQ-4963 | evolution, taxonomy
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but do not breed freely with members of another species in the wild.
That last part takes care of the ligers and tiglons. But what if we consider plants? Under the definition I just gave, most grasses (around 11,000 species) would have to be considered as one species. In the wild, most grasses will freely pollinate related species and produce hybrid seed, which germinates. You might then think we could just modify the definition to specify that the offspring must be fertile (i.e. able to reproduce with one another)...
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but do not breed freely with members of another species in the wild to produce fertile progeny.
Unfortunately, the situation is still more complicated (we've barely started!). Often wild hybridisation events between plants lead to healthy, fertile offspring. In fact common wheat (Triticum aestivum) is a natural hybrid between three related species of grass. The offspring are able to breed freely with one another.
Perhaps we could account for this by taking into account whether the populations usually interbreed, and whether they form distinct populations...
The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of populations or meta-populations of related individuals that resemble one another, are able to breed among themselves, but do tend not to breed freely with members of another species in the wild to produce fertile progeny.
The following is multiple choice question (with options) to answer.
The earth’s biomes are categorized into two major groups named what? | [
"terrestrial and galactic",
"aquatic and galactic",
"terrestrial and aquatic",
"icelandic and aquatic"
] | C | 44.3 | Terrestrial Biomes By the end of this section, you will be able to: • Identify the two major abiotic factors that determine terrestrial biomes • Recognize distinguishing characteristics of each of the eight major terrestrial biomes The Earth’s biomes are categorized into two major groups: terrestrial and aquatic. Terrestrial biomes are based on land, while aquatic biomes include both ocean and freshwater biomes. The eight major terrestrial biomes on Earth are each distinguished by characteristic temperatures and amount of precipitation. Comparing the annual totals of precipitation and fluctuations in precipitation from one biome to another provides clues as to the importance of abiotic factors in the distribution of biomes. Temperature variation on a daily and seasonal basis is also important for predicting the geographic distribution of the biome and the vegetation type in the biome. The distribution of these biomes shows that the same biome can occur in geographically distinct areas with similar climates (Figure 44.12). |
SciQ | SciQ-4964 | human-biology, endocrinology, organs
Title: Is there a blood panel lab test that measures all the hormone-producing glands? I understand that there are gland-specific hormone tests, such as:
Secretin: for the pancreas; and
Prolactin/ACTH: for the pituitary; and
PTH: for the payathyroid, etc.
However, are there any "composite" blood panels that test the "entire gamut/spectrum" of organs/glands, similar to what composite metabolic panels do for your cell counts? There are no composite tests that measure all the clinically important hormone producing glands. There are too many hormones produced by too many hormone producing cells/tissues in the body to test for all of them all at once (i.e. in a panel).
For illustrative purposes only... if you go to wikipedia they have a list of all hormones in the human body which is definitely far from complete! But it gives you an indication of just "how many" hormones there are and why testing for all of them is impossible in a panel.
Even with regard only to pancreatic hormones, there are several hormones produced (e.g. insulin, glucagon, somatostatin) that aren't necessarily a marker of the glands overall function (because they are not necessarily involved in the same function). Each of these hormones has different functions even though they are produced by the same gland.
Regardless, from a medical perspective you would never have a reason to test for all of them anyway. If you tested enough of them you'd find at least one of them that would - by chance - be abnormal.
Additionally, if you asked a handful of scientists to name fifty hormones there would be a lot of different hormones on each of their lists. The definition of hormone is vague, and we are learning more about new hormones every day. In the last decade we have learned that bile acids - chemicals predominately produced by the liver that are involved in dietary fat absorption - also act as hormones. There aren't clinical reasons to study all of these molecules just yet, but this demonstrates that it would be impossible to measure all of them all at the same time in one particular "panel".
The following is multiple choice question (with options) to answer.
What does the thymus gland produce? | [
"t cells",
"hormones",
"insulin",
"b cells"
] | A | Organs of the lymphatic system include the tonsils, thymus gland and spleen. The thymus gland produces T cells or T-lymphocytes (see below) and the spleen and tonsils help in fighting infections. The spleen’s main function is to filter the blood. The spleen also detects viruses and bacteria and triggers the release of pathogen fighting cells. |
SciQ | SciQ-4965 | cell-biology, meiosis, mitosis
Title: Is the cell cycle applicable to meiosis as well, or just mitosis? All the diagrams I can find, show the cell cycle as having G1 phase (growth 1), S phase (DNA replication), G2 (growth 2) before the Mitotic phase (mitosis + cytokinesis).
Is there an equivalent "cell cycle" for meiosis, since the chromosomes in parent cell in meiosis also having "double" the genetic material prior to cell division (presumably from DNA replication too)?
Is it simply the same cell cycle as mitosis but with a Meiotic phase instead of Mitotic?
If so, would appreciate if anyone had a diagram :) Thanks! The cell cycle is only associated with mitosis. The cell cycle is the normal process of cell division with which cells can indefinitely increase their number by cyclically repeating the process. When a cell goes through the cycle, the result is two cells that are genetically identical.
Meiosis is a special type of cell division (which can occur only in eukaryotes) that produces cells that are not genetically identical to the initiating cell. The number of chromosomes in each of the resulting cells is half the number that were in the initial cell. (These haploid cells can later participate in fertilization, producing a cell with the original number of chromosomes.) Many of the steps of meiosis are similar to the steps involved in mitosis, but overall the process is more complex. Since meiosis reduces the number of chromosomes, it cannot be repeated and so does not take part in a cell division cycle.
The following is multiple choice question (with options) to answer.
During which phase does dna replication occur in the cell cycle? | [
"mitosis",
"resting",
"synthesis",
"gap"
] | C | 9.2 | DNA Replication By the end of this section, you will be able to: • Explain the process of DNA replication • Explain the importance of telomerase to DNA replication • Describe mechanisms of DNA repair When a cell divides, it is important that each daughter cell receives an identical copy of the DNA. This is accomplished by the process of DNA replication. The replication of DNA occurs during the synthesis phase, or S phase, of the cell cycle, before the cell enters mitosis or meiosis. The elucidation of the structure of the double helix provided a hint as to how DNA is copied. Recall that adenine nucleotides pair with thymine nucleotides, and cytosine with guanine. This means that the two strands are complementary to each other. For example, a strand of DNA with a nucleotide sequence of AGTCATGA will have a complementary strand with the sequence TCAGTACT (Figure 9.8). |
SciQ | SciQ-4966 | analytical-chemistry, intermolecular-forces
Title: If polar non-polar intermolecular forces are stronger, why do polar compounds elute first in GC? I remembering reading that the interaction between a polar molecule and non-polar molecule is stronger than the interaction between two non-polar molecules.
However, in analytical chemistry classes, we are told that polar molecules elute first in a Gas Chromatograph that has a non-polar column. According to http://www.chem.ucla.edu/~bacher/General/30BL/gc/theory.html
If the polarity of the stationary phase and compound are similar, the retention time increases because the compound interacts stronger with the stationary phase. As a result, polar compounds have long retention times on polar stationary phases and shorter retention times on non-polar columns using the same temperature.
The following is multiple choice question (with options) to answer.
What kind of interactions do polar substances experience? | [
"monopole-dipole interactions",
"dipole-dipole interactions",
"monopole-monopole interactions",
"axial interactions"
] | B | Substances that are polar experience dipole-dipole interactions. |
SciQ | SciQ-4967 | cellular-respiration, glucose, fermentation
The so-called cycle of Cori & Cori
In my opinion it is best to approach glycolysis as I have done above, without reference to the tissue or organism, so as to understand the essential features of the process.
In the specific case of mammals, some tissues perform glycolysis anaerobically, e.g. the red blood cell (which lacks mitochondria) or rapidly excercising muscle (where the blood supply and number of mitochondria are not sufficient to generate ATP for muscle contraction. The liver, in contrast, has a plentiful supply of oxygen and hence NAD+, and so can reoxidize lactate to pyruvate if the former is transported in the blood from the anaerobic tissue to the liver, salvaging the carbon skeleton.
Under conditions of low blood sugar (e.g. starvation) it is important that the pyruvate be reconverted into glucose in the liver by gluconeogenesis, rather than be converted to other products, and the glucose is released into the blood. In this case one goes full circle, this process is generally referred to as the Cori Cycle. I always avoided this term myself in teaching students as I found it caused confusion with cycles such as the tricarboxylic acid cycle and the urea cycle, where all the chemical interconversions take place in the same tissue.
Footnote: Glycolysis under aerobic conditions
Under aerobic conditions (e.g. in the liver after a carbohydrate meal) the purpose of glycolysis is not primarily to generate energy but to utilize the glucose, storing it as fat (after glycogen capacity is reached) or using it to synthesize intermediates. There are different fates for the pyruvate (acetyl-CoA is shown), but lactate is not one of them as the NADH can be reoxidized far more efficiently in the mitochondria, with molecular oxygen being the ultimate oxidizing agent.
Text References
Berg et al. Section. 16.1 (5th ed.) covers glycolysis in great detail under aerobic conditions. The lactic dehydrogenase reaction is given little emphasis, but can be found in section 16.1.9.
The following is multiple choice question (with options) to answer.
Which process is glycolysis in during cellular respiration? | [
"aerobic",
"anaerobic",
"enzymatic",
"hydrolysis"
] | B | Cellular respiration occurs in three stages: glycolysis, the Krebs cycle, and electron transport. Glycolysis is an anaerobic process. The other two stages are aerobic processes. |
SciQ | SciQ-4968 | organic-chemistry, nomenclature, hydrocarbons
Title: Preferred IUPAC names for branched unsaturated hydrocarbons (polyenes)?
What are the preferred IUPAC names for the following three compounds?
Compound 1 is 3-ethenylhexa-1,5-diene. 2 is 3-methylidenehexa-1,5-diene.
But I am still not sure about 3. I have narrowed it down to two choices: 3-ethylidenehexa-1,5-diene or 4-ethenylhexa-1,4-diene.
How do I decide which two of the three double bonds should be in the parent chain, considering that both choices of parent chain have the same number of complex and double bonds?
The information I used is from the following Q&As:
How is a side-group that contains a double bond named?
How do you name an alkene using IUPAC rules if the longest carbon chain in this alkene does not include the double bond? According to the general methodology described in the current version of Nomenclature of Organic Chemistry – IUPAC Recommendations and Preferred Names 2013 (Blue Book), a double bond is expressed by changing the ending ‘ane’ of the name of the corresponding saturated parent structure to ‘ene’.
P-31.1.1.1 The presence of one or more double or triple bonds in an otherwise saturated parent hydride (…) is denoted by changing the ending ‘ane’ of the name of a saturated parent hydride to ‘ene’ or ‘yne’. Locants as low as possible are given to multiple bonds as a set, even though this may at times give ‘yne’ endings lower locants than ‘ene’ endings. If a choice remains, preference for low locants is given to the double bonds. In names, the ending ‘ene’ always precedes ‘yne’, with elision of the final letter ‘e’ in ‘ene’. Only the lower locant for a multiple bond is cited, except when the numerical difference between the two locants is greater than one, in which case the higher locant is enclosed in parentheses.
(…)
For example:
The following is multiple choice question (with options) to answer.
Saturated hydrocarbons are given the general name of what? | [
"lipids",
"alkanes",
"carbohydrates",
"enzymes"
] | B | Saturated hydrocarbons are given the general name of alkanes. The name of specific alkanes always ends in –ane and has a prefix to indicate how many carbon atoms it has. |
SciQ | SciQ-4969 | transcription, translation
Ralston, A. (2008) Operons and prokaryotic gene regulation. Nature Education
From Genes to Genomes: Concepts and Applications of DNA Technology
Molecular cell biology
Analysis of Genes and Genomes
The following is multiple choice question (with options) to answer.
In the cellular process of transcription, dna code is converted into what other kind of code? | [
"fna",
"sna",
"rna",
"dpa"
] | C | 3.4 Protein Synthesis DNA stores the information necessary for instructing the cell to perform all of its functions. Cells use the genetic code stored within DNA to build proteins, which ultimately determine the structure and function of the cell. This genetic code lies in the particular sequence of nucleotides that make up each gene along the DNA molecule. To “read” this code, the cell must perform two sequential steps. In the first step, transcription, the DNA code is converted into a RNA code. A molecule of messenger RNA that is complementary to a specific gene is synthesized in a process similar to DNA replication. The molecule of mRNA provides the code to synthesize a protein. In the process of translation, the mRNA attaches to a ribosome. Next, tRNA molecules shuttle the appropriate amino acids to the ribosome, one-by-one, coded by sequential triplet codons on the mRNA, until the protein is fully synthesized. When completed, the mRNA detaches from the ribosome, and the protein is released. Typically, multiple ribosomes attach to a single mRNA molecule at once such that multiple proteins can be manufactured from the mRNA concurrently. |
SciQ | SciQ-4970 | homework-and-exercises, forces, torque, gyroscopes, applied-physics
Please note that I am a beginner (maybe intermediate) at physics.
A spinning gyroscope has an angular momentum vector $\vec L$ pointing along its axis, given by the right-hand rule. Gravity exerts a torque on the gyroscope, trying to rotate it around an axis perpendicular to its current axis, changing its angular momentum by $d\vec L$ in a time $dt$. Since the axes are perpendicular, $\vec L$ and $d\vec L$ are perpendicular. Thus, the magnitude of the angular momentum does not change, only its direction is changing, causing it to precess. Torque is the rate of change of angular momentum: $$\vec{\tau} = \vec r \times \vec F = \frac{d \vec L}{dt}$$ The ground exerts a normal force, equal to the weight in magnitude, upwards on the point of contact with the ground, while the weight pulls it down at the disk, forming a torque couple given by $\vec r \times \vec F = rF \sin \theta$ above, where $\vec r$ is the vector from the point of contact to the disk and $\theta$ is the angle of the axis from the vertical. The height of the disc above the point of contact with the ground, which is proportional to $r$, affects the lever arm of gravity, causing a larger torque when the gyroscope is "taller" and smaller torque when the gyroscope is "shorter". We are assuming that the point of contact with the ground does not slip/move, and hence using it as our origin.
The size of the disc affects its moment of inertia. Torque is the rate of change of angular momentum with respect to time. The larger and heavier the disc, the greater its moment of inertia and angular momentum and the more resistant it is to changes in its angular momentum and will thus precess more slowly. This is also why the gyroscope precesses faster and faster as it slows down due to friction.
The following is multiple choice question (with options) to answer.
If a gyroscope is not spinning, it acquires angular momentum in the direction of what? | [
"gravity",
"velocity",
"torque",
"acceleration"
] | C | This same logic explains the behavior of gyroscopes. Figure 10.31 shows the two forces acting on a spinning gyroscope. The torque produced is perpendicular to the angular momentum, thus the direction of the torque is changed, but not its magnitude. The gyroscope precesses around a vertical axis, since the torque is always horizontal and perpendicular to L . If the gyroscope is not spinning, it acquires angular momentum in the direction of the torque ( L falling over just as we would expect. |
SciQ | SciQ-4971 | immunology, pathology, pathophysiology
SRC
You can see in healthy phagocytes that through one of two pathways, protein antigens end up displayed on HLA molecules for cellular immunity to take over. Option B is that another cell like a macrophage detects distress signals from the infected cell and induces cell death in it through receptors or oxidative burst. In the case of Salmonella, HLA expression is down-regulated and oxidative burst can be inhibited so localized, infected antigen-presenting cells cant mount an effective response.
That's not to say everything is de-regulated early on. If you succeed in antigen presentation or innate killing (perhaps a non-pathogenic strain), you will resolve the infection as seen in the above figure: a combination of T-mediated killing, B-mediated killing, NK-mediated killing, and generalized inflammation.
In the chronic case, the pathogen will have escaped the primary immune response, but the system will attempt to continue to resolve the infection. This can lead to a number of things: cellular anergy, cellular hyperactivity, sequestration (see granuloma), chronic inflammation & tissue damage, and so forth. The following diagram is predicated upon viral infections but the immunology is largely similar:
SRC
There are changes to the system that are a result of over-exposure to antigen, and an inability to clear that stimulation. The best way to explain it is that chronic stimulation leads to both hyperactivity and suppression. The constant presence of effector molecules like TNF-a leads to a persistent state of tissue inflammation, which is bad for the tissue, but taken together with the persistent presence of antigen, this may lead to dysfunctional responses by lymphocytes (3).
A particularly virulent infection may be impossible for your immune system to clear without assistance, then, requiring the intervention of gram-negative antibiotics, for example.
The following is multiple choice question (with options) to answer.
Which leukocytes are first to respond to bacterial infections? | [
"microcytes",
"neutrophils",
"chemocytes",
"erythrocytes"
] | B | 18.4 Leukocytes and Platelets Leukocytes function in body defenses. They squeeze out of the walls of blood vessels through emigration or diapedesis, then may move through tissue fluid or become attached to various organs where they fight against pathogenic organisms, diseased cells, or other threats to health. Granular leukocytes, which include neutrophils, eosinophils, and basophils, originate with myeloid stem cells, as do the agranular monocytes. The other agranular leukocytes, NK cells, B cells, and T cells, arise from the lymphoid stem cell line. The most abundant leukocytes are the neutrophils, which are first responders to infections, especially with bacteria. About 20–30 percent of all leukocytes are lymphocytes, which are critical to the body’s defense against specific threats. Leukemia and lymphoma are malignancies involving leukocytes. Platelets are fragments of cells known as megakaryocytes that dwell within the bone marrow. While many platelets are stored in the spleen, others enter the circulation and are essential for hemostasis; they also produce several growth factors important for repair and healing. |
SciQ | SciQ-4972 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
What thin whip-like structures help prokaryotes move toward food or away from toxins? | [
"sporangia",
"flagella",
"cilia",
"antennae"
] | B | Most prokaryotes have one or more long, thin "whips" called flagella (flagellum, plural) . You can see flagella in Figure below . Flagella help prokaryotes move toward food or away from toxins. Each flagellum spins around a fixed base. This causes the cell to roll and tumble. |
SciQ | SciQ-4973 | organic-chemistry, everyday-chemistry, experimental-chemistry, biochemistry, food-chemistry
Title: How Bread is made with yeast, sugar and luke warm milk? Materials and Apparatus:
wheat flour
sugar
dry yeast
glass bowl
covering plate
milk
Procedure:
Lukewarm milk is taken in the glass bowl and sugar is added to it. Then, yeast is added to the same.
The mixture is left undisturbed for 10-12 minutes to activate the yeast
3 cups of wheat flour are added to the bowl containing the milk mixture.
The mixture is mixed thoroughly with 100ml of added water and the dough is kneaded well
The dough is placed in a bowl, covered with a plate and left undisturbed for 2 hours.
My query/confusion:
Why is milk needed?
"activated yeast"- what's the difference?
Can yeast work without sugar or milk.
Detail out the stages of the anaerobic oxidative process which takes place as a common first step in both aerobic and anaerobic respiration.
Finally, feel free to share anything I may be missing which should be here.
If you have any confusion regarding what I want to ask, please ask in the comments. Please upvote if you are curious about it too
milk is not needed, 'pure' bread is without milk
yeast is a fungus, therefore, it is alive. Its best to work with fresh yeast, which you find as small cubes in the refrigerated section. This one does not have to be activated. non-fresh yeast is dried, so in order for it to work properly, it has to be undried by adding water, which is called activation.
and 4. As said before, milk is not needed. Sugar however is the food for the yeast, without it, it does nothing. In aerobic breathing, the yeast metabolizes the sugar as we would: sugar + oxygen -> water + CO2. Without oxygen, the yeast resorts to ethanol fermentation: sugar -> alcohol + CO2 (this is, why it is used to make beer or wine). For making bread, we have a mixture of both respirations, which does not really matter, since we are only interested in the CO2, which makes the dough fluffy =) But without sugar, there is no CO2.
The following is multiple choice question (with options) to answer.
What common process is used in the production of bread, cheese and alcoholic beverages? | [
"cloning",
"condensation",
"fermentation",
"oxidation"
] | C | agents of fermentation in the production of bread, cheeses, alcoholic beverages, and numerous other food preparations. Secondary metabolites of fungi are used in medicine as antibiotics and anticoagulants. Fungi are used in research as model organisms for the study of eukaryotic genetics and metabolism. |
SciQ | SciQ-4974 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
Comprising 10 percent of the mass of the brain, what structure has varied functions that all point to a role in the motor system? | [
"medulla oblongata",
"cerebrum",
"cerebellum",
"superior peduncle"
] | C | 16.5 | The Coordination and Gait Exams By the end of this section, you will be able to: • Explain the relationship between the location of the cerebellum and its function in movement • Chart the major divisions of the cerebellum • List the major connections of the cerebellum • Describe the relationship of the cerebellum to axial and appendicular musculature • Explain the prevalent causes of cerebellar ataxia The role of the cerebellum is a subject of debate. There is an obvious connection to motor function based on the clinical implications of cerebellar damage. There is also strong evidence of the cerebellar role in procedural memory. The two are not incompatible; in fact, procedural memory is motor memory, such as learning to ride a bicycle. Significant work has been performed to describe the connections within the cerebellum that result in learning. A model for this learning is classical conditioning, as shown by the famous dogs from the physiologist Ivan Pavlov’s work. This classical conditioning, which can be related to motor learning, fits with the neural connections of the cerebellum. The cerebellum is 10 percent of the mass of the brain and has varied functions that all point to a role in the motor system. |
SciQ | SciQ-4975 | rna-sequencing, sequence-analysis
It seems to me that both the polyA sequences at the end are some sort of tail rather than actual coding for poly lysines. If we BLAST either of the sequences, the polyA part doesn't align with any reliable nucleotide or protein (i.e., with the NCBI non-redundant databases). I can give more examples and show their best alignments to nr-Sequences but it will make the question too long.
Cross posted to SeqAnswers. The CATGTC sequence at the end of the poly A tail is an artefact of the method used in constructing the original cDNA library.
According to https://www.ncbi.nlm.nih.gov/nucest/EE485195.1 this EST comes from a library constructed in the Clontech vector pDNR-LIB
The Clontech SMART cDNA cloning system manuals are linked to from here
and the general manual descibes the use of a primer for 1st strand synthesis:
CDS III/3' PCR Primer 5'-ATTCTAGAGGCCGAGGCGGCCGACATG-d(T)30N-1N-3'
(N = A, G, C, or T; N-1 = A, G, or C)
If you look carefully at the primer you will see that the oligo dT portion, designed to anneal to the poly-A tail of the mRNA is preceded by the sequence GACATG and a SfiI site that is used in some clever cloning strategy that I don't fully understand. What is clear however is that the use of this primer will put CATGTC immediately after the poly A in the cDNA:
.....SfiI....
5'-ATTCTAGAGGCCGAGGCGGCCGACATGTTTTTTTTTTTTTTTTTTT...
TAAGATCTCCGGCTCCGCCGGCTGTACAAAAAAAAAAAAAAAAAAA...5'
>>> turning bottom strand around - 5' ...AAAAAAACATGTC
The following is multiple choice question (with options) to answer.
What is a segment of dna that carries a code for making a specific polypeptide chain called? | [
"nucleotide",
"amino acid",
"a gene",
"a protein"
] | C | Each particular organism contains many protein molecules that are specific to that organism. The particular base sequence of DNA is responsible for the production of all of the different proteins that are present in each and every living thing that has ever inhabited the Earth. How does that work? Cells use the unique sequence of DNA bases to decide which proteins to synthesize. A gene is a segment of DNA that carries a code for making a specific polypeptide chain. The cell essentially decodes the DNA in order to make whatever peptides and proteins are needed by that organism. |
SciQ | SciQ-4976 | human-biology, immunology, medicine, vaccination, antigen
Title: How does adjuvant enhance the immunogenicity of antigen? My question is, How does adjuvant enhance immunogenicity of antigen?
I just want to know deeply about it , Any suggestions will be helpful! This is a quick answer to a very broad question since the mechanisms of adjuvants are very different. I'll try to summarize just a few. For a deeper understanding please start reading this paper and its references.
1) Aluminum salts (aluminum phosphate or hydroxide)
Studies suggest alum salts work by causing the formation of an antigen
depot at the inoculation site from where the antigen is released slowly.
The trapping of soluble antigen in the alum gel may also increase the
duration of antigen interaction with the immune system. Other
mechanisms of action involve complement, eosinophil, and macrophage,
activation and increased efficiency of antigen uptake by antigen
presenting cells seen with particulate matter with a size under 10
micron.
2) Calcium salts
They work pretty much like aluminum salts but they are much better tolerated by the organism.
3) Bacteria-derived (peptidoglycan or lipopolysaccharide)
They are naturally recognized by the immune system and for this reason, they are used to simply boost the immune response.
4) Emulsions
They form a depot at the injection site, enabling the slow release of antigen. The immune system has more time to recognize the antigen and react.
5) Liposomes
They help to extend the half-life of antigens in the blood leading to a higher antigen exposure to antigen presenting cells after vaccination. A Very similar effect is achieved using microbeads made of artificial polymers.
The following is multiple choice question (with options) to answer.
Introduction of antigens into the body through immunization can confer what benefit? | [
"active respiration",
"active immunity",
"growth rate",
"sensitive immunity"
] | B | |
SciQ | SciQ-4977 | neuroscience, brain, neuroanatomy, neurology
Title: Why do humans alone have the capability to have religious/spiritual experiences? What is it in our brain that makes having such experiences possible? I assume other species don't have these. Sure there are instances in the natural world where you can see individuals of the species gather around the dead one. Sometime even the alpha male in the group allows the kin/relatives of the dead individual to approach it (for whatever reason).
The kind of thing I don't see in the wild-life kingdom is an individual becoming "enlightened" or the likes.
Sure our cerebrum is highly developed and all. But "what" is it in our brain that makes it capable for humans to have such experiences?
I've read articles saying we have identified such regions in the brain. Just want to know what these structures are. Did such research establish that such structures also exist in other species too? Its not clear that this is true.
Working with animals has been a little disconcerting over the past 50-60 years. In the distant past, I think most evolutionary anthropologists and their like bought into the idea that humans were completely uniquely intelligent and spiritual. But the more we try to define human sensibilities apart from other animals, the more we find its difficult to see animals as being completely incapable of human feelings and even thoughts.
I refer you to this question which describes the shift in intelligence theories over the years: Why have humans evolved conciousness?
The above reference is just to say that every definition of intelligence that is fairly broad has been overturned by animals (thumbs, socialization, tool use, self awareness, communication and language).
If you want to say 'I know we're special, but I just can't say how' you are in lots of good company... it's become pretty hard to lay down a definition that includes all human beings and excludes animals.
The following is multiple choice question (with options) to answer.
What part of the brain is largest in intelligent mammals? | [
"manubrium",
"cortex",
"thallus",
"cerebrum"
] | D | In intelligent mammals, such as primates, the cerebrum is larger compared to the rest of the brain. A larger cerebrum allows primates to develop higher levels of intelligence. Primates have the ability to learn new behaviors. They also engage in complex social interactions, such as fighting and play. |
SciQ | SciQ-4978 | fluid-dynamics, waves, geophysics
Title: What is the dominant cause for ocean waves at a beach? What is the dominant cause for ocean waves at a beach? Are they the result of wind/pressure difference? If so, the waves do seem to exist in similar intensity even during relative quiet times of the day.
Is there a simple mathematical model that we can quickly explain the intensity/frequency of waves with? Does the strength of the waves (say the variance and mean of the amplitude of waves) relate to a simple physical quantity (temperature, off shore wind, pressure difference)? Yes, primarily wind. It's called the Kelvin-Helmholtz instability. Strong winds in an area will excite a range of wavelengths, the longer wavelengths will go faster according to the deep water dispersion relation ( speed proportional to square root of wavelength). So if you see a train of waves with decreasing wavelength over time, you could in principle infer a common point of origin (this is a common textbook or qualifying exam type problem).
The following is multiple choice question (with options) to answer.
What is the cause of most ocean waves? | [
"Gravity",
"Magnetic pull",
"winds",
"tides"
] | C | Most ocean waves are caused by winds. The size of a wave depends on how fast, how far, and how long the wind blows. Tsunamis are waves caused by earthquakes. |
SciQ | SciQ-4979 | atmosphere, wind, geography, troposphere, stratosphere
Title: Other than the South Pole where is the windless place on Earth? For this other question "Would this chambered cylinder be possible", preferably near the equator where is a calmest place from the troposphere to the stratosphere where is the windless place one Earth most of the year? Not just the south pole, but 'Ridge A' and many other parts of the high Antarctic Plateau, at or about 4000 metres altitude, are generally recognized as being the least windy. Otherwise, there are a many parts of the high pressure belts at about +/- 30 degrees which have little wind for most of the year. These tend to be very dry deserts where occasional winds have momentum from other regions. On a local scale there are some deep valleys in tropical rain forests. Once you get below the canopy turbulence level they seldom receive winds of any significance - just the lightest breeze from impeded convection. However, records are hard to find because anemometers in such locations are not really representative of anything.
There is an instagram which claims that Fern tree bus stop, in Hobart, Tasmania, is the 'calmest place on Earth'.
But my experience of Hobart is that icy winds in winter can be far from calm.
These things are relative. Compared to the 2100 km/hour winds of Neptune, everywhere on our planet is as close to windless as makes no difference.
The following is multiple choice question (with options) to answer.
What is the lowest layer of the atmosphere called? | [
"troposphere",
"lithosphere",
"mesosphere",
"asthenosphere"
] | A | Air movement takes place in the troposphere. This is the lowest layer of the atmosphere. Air moves because of differences in heating. These differences create convection currents and winds ( Figure below ). |
SciQ | SciQ-4980 | evolution, zoology, anatomy, species
Title: Examples of animals with 12-28 legs? Many commonly known animals' limbs usually number between 0 and 10. For example, a non-exhaustive list:
snakes have 0
Members of Bipedidae have 2 legs. Birds and humans have 2 legs (but 4 limbs)
Most mammals, reptiles, amphibians have 4 legs
Echinoderms (e.g., sea stars) typically have 5 legs.
Insects typically have 6 legs
Octopi and arachnids have 8 legs
decapods (e.g., crabs) have 10 legs
....But I can't really think of many examples of animals containing more legs until you reach 30+ legs in centipedes and millipedes. Some millipedes even have as many as 750 legs! The lone example I am aware of, the sunflower sea star, typically has 16-24 (though up to 40) limbs.
So my question is: what are some examples of animals with 12-28 legs? As a couple of counterexamples, species in the classes Symphyla (Pseudocentipedes) and Pauropoda within Myriapoda have 8-11 and 12 leg pairs respectively, so between 16 to 24 legs (sometimes with one or two leg pair stronlgy reduced in size).
(species in Symphyla, from wikipedia)
Another common and species-rich group with 14 walking legs (7 leg pairs) is Isopoda.
(Isopod, picture from wikipedia)
You also need to define 'legs' for the discussion to be meaningful. As you say, decapods have 10 legs on their thoracic segments (thoracic appendages), but they can also have appendages on their abdomens (Pleopods/swimming legs), which will place many decapods in the 10-20 leg range.
(Decapod abdominal appendages/legs in yellow, from wikipedia)
So overall, in Arthropoda, having 12-28 legs doesn't seem all that uncommon. There are probably other Arthropod groups besides those mentioned here that also have leg counts in this range.
However, for a general account, the most likely answer (if there is indeed a relative lack of 12-28 legged animals) is probably evolutionary contingencies and strongly conservative body plans within organism groups.
The following is multiple choice question (with options) to answer.
What is the biggest group of animals on the planet? | [
"arthropods",
"herbivores",
"mammles",
"carnivores"
] | A | How often do you think you see an arthropod? Well, have you ever looked up close at an ant? A spider? A fly? A moth? With over a million described species (and many more yet to be described) in the phylum containing arthropods, chances are, you encounter one of these organisms every day, without even leaving your house. Arthropods are a very diverse group of animals. In fact, they are the biggest group of animals on the planet, with upwards of 5 million distinct species. |
SciQ | SciQ-4981 | physical-chemistry, acid-base, equilibrium
You have a solution of weak base. You add a stronger base. The increase in hydroxide concentration leads, by Le Chatelier's principle, to a lower extent of dissociation.*
This is beyond the scope of Ostwald's law, which tacitly assumes the lack of what amounts to a common-ion effect. Ostwald's law holds if the solvent which you're using to dilute your solution does not interfere (or interferes only weakly) with your electrolyte's solubility; the added solvent must serve to decrease the concentration of your electrolyte. Evidently, then, adding a stronger base will interfere with the solubility of your weak base, and is not governed by Ostwald's law.
The following is multiple choice question (with options) to answer.
The presence of solute particles blocks some of the ability for liquid particles to do what? | [
"evaporate",
"dissolve",
"fuse",
"melt"
] | A | The presence of solute particles blocks some of the ability for liquid particles to evaporate. Thus, solutions of solid solutes typically have a lower vapor pressure than the pure solvent. |
SciQ | SciQ-4982 | inorganic-chemistry, coordination-compounds, transition-metals, color
Title: How can we predict the colour of transition metal complexes? I am facing problems in indentifying colour of complex compunds just by seeing the their molecular formula. Is there any method or concept to predict the colour of complex compunds? The basic principle of coloured compounds is that there is some kind of electronic transition whose energy difference corresponds to a photon whose wavelength is in the visible region ($\pu{400nm}<\lambda<\pu{700nm}$). Thus, to determine the colour of a compound we should always be looking at the molecular orbital scheme; for reference, I have attached the MO scheme of a typical octahedral $\ce{[ML6]^n+}$ compound in figure 1.
The following is multiple choice question (with options) to answer.
What are color and hardness physical properties of? | [
"elements",
"cells",
"ions",
"matter"
] | D | A: You can see that snow and sand have a different color. You can also feel that snow is softer than sand. Both color and hardness are physical properties of matter. |
SciQ | SciQ-4983 | biochemistry, endocrinology, cell-signaling
Title: Effect of steroid hormone on specific cells? As steroid hormones can pass through the plasma membrane by simple diffusion because they are lipid derived hormones, it means that they are capable of passing through every cell of our body, BUT why are only specific cells responsive against steroid hormones?
For example, all of our body cells almost contains the genes for the development of secondary sexual characters but why do only specific cells show a response against these steroid hormones because the development of secondary sexual characters occur only in specific region of our body, that is, beard formation occur only in a specific region of the face, etc.
IN SUMMARY: When steroid hormones can pass through every cell of our body then why do they show only a localized response? Unlike other types of hormones, steroid hormones do not have to bind to plasma membrane receptors. Instead, they can interact with intracellular receptors that are themselves transcription activators. Steroid hormones too hydrophobic to dissolve readily in the blood travel on specific carrier proteins from their point of release to their target tissues. In the target tissue, the hormone passes through the plasma membrane by simple diffusion and binds to its specific receptor protein in the cytoplasm. The receptor-hormone complex then translocates into the nucleus where it acts by binding to highly specific DNA sequences called hormone response elements (HREs), thereby altering gene expression.
Hormone binding triggers changes in the conformation of the receptor proteins so that they be- come capable of interacting with additional transcription factors. The bound hormone-receptor complex can either enhance or suppress the expression of adjacent genes.
The DNA sequences (HREs) to which hormone- receptor complexes bind are similar in length and arrangement, but differ in sequence, for the various steroid hormones. Each receptor has a consensus HRE sequence to which the hormone-receptor complex binds well, with each consensus consisting of two six-nucleotide sequences, either contiguous or separated by three nucleotides,
The ability of a given hormone to act through the hormone-receptor complex to alter the expression of a specific gene depends on the exact sequence of the HRE, its position relative to the gene, and the number of HREs associated with the gene.
The following is multiple choice question (with options) to answer.
What are steroid hormones made of? | [
"organisms",
"lipids",
"water",
"amino acid"
] | B | Steroid hormones are made of lipids, such as phospholipids and cholesterol. They are fat soluble, so they can diffuse across the plasma membrane of target cells and bind with receptors in the cytoplasm of the cell (see Figure below ). The steroid hormone and receptor form a complex that moves into the nucleus and influences the expression of genes, essentially acting as a transcription factor. Examples of steroid hormones include cortisol and sex hormones. |
SciQ | SciQ-4984 | human-biology, microbiology, virology, medicine, infection
So, for about 3 L of blood serum in a person, that's 3 * 10^11 copies of the viral genome in the blood as a threshold for survival. I couldn't find useful information about viral load in organs and other tissue, but since blood has been claimed to have much higher concentration of virus than saliva or other fluids, we can assume this number is a significant portion of the total load. I'll assume about a third, so we get 10 ^ 12 genome copies. Some or even most of these RNA genomes might not be incorporated into viral particles but counting actual viral particles is very difficult, so no-one has published a correlation between Q-RT-PCR results and infectious particle counts as far as I could find.
Next, we need to estimate the number of progeny viruses that each infected cell produces. In Clin Diagn Lab Immunol. 2002 Jan; 9(1): 19–27. , researchers got about 2 * 10^4 PFU from wells containing 2-4 * 10^6 alveolar macrophage cells each. In these wells, 50-60% of the cells had detached from the walls, compared to 0 in non-infected wells. This implies that, for macrophages at least, about 100 infected cells make enough virus to create one plaque in the assay they used. In J Virol. 2015 Jul 1; 89(13): 6773–6781. about 1000 particles per PFU are reported for the 12th passage of virus in their Vero cell assay system, so 10 virus particles per infected cell. We estimated 10^12 virus particles earlier, so that implies about 10^11 cells were infected. That's a similar number as estimated for HIV in the comments of that question you linked. At about 3 * 10^13 human cells in the body, that's about 0.3 % of all cells.
Each of the studies I've linked here is quite different from the other, so plugging results from one into the other is introducing a lot of error, but hopefully the process was informative.
The following is multiple choice question (with options) to answer.
How many processes contribute to the emergence of viral diseases? | [
"two",
"four",
"three",
"one"
] | C | |
SciQ | SciQ-4985 | earthquakes, seismology, instrumentation, in-situ-measurements, diy
Title: Using accelerometer as a seismograph I'm using ADXL345 accelerometer with Raspberry Pi to build a seismograph. I've successfully hooked it up and can plot the accelerometer data in three axis. Is there any way to express these data in the form of the magnitude of an earthquake, of course, at the point of sensing? I know that it might be imprecise, but any representation would be helpful (e.g. Richter scale), and how to accomplish that. The magnitude of an earthquake is related to the total energy released, therefore to estimate it from a seismogram you need to know the distance to the source. In the case of the Richter scale for example, the relationship between magnitude and seismogram amplitude is defined for a standard distance.
If you have only one seismograph, you can not triangulate the location of the source (hypocenter). Therefore, you can not estimate the magnitude of a seismic event (Richter or moment magnitude).
But you can estimate the local seismic intensity of the event at the particular location of your instrument. With the accelerometer data you can easily measure the peak ground acceleration, that can be used to estimate the intensity in any of the existing scales. For example, the peak ground accelerations associated to each intensity level in the commonly used Mercalli intensity scale are:
Those g values would be easy to calculate with the accelerometer data and proper calibration constants.
Table taken from the Wikipedia page for peak ground acceleration
You might want to have a look at this question. There are some nice answers and references that you might find useful.
The following is multiple choice question (with options) to answer.
What type of scale is the richter scale? | [
"logarithmic",
"asymmetric",
"algorithmic",
"dimensional"
] | A | 7. Like the Richter scale, the moment magnitude scale is logarithmic. The 2011 Tōhoku earthquake in Japan was 9.0 and did tremendous damage. A few months earlier, an 8.8 struck Chile and did much less damage. Why?. |
SciQ | SciQ-4986 | geology, soil, mapping, regional-geology
Title: What is the average color of soil? Where I live the soil is red.
Is there a map or chart where you can see the average color of the dirt according to geographical location? What would the color be if all of the dirt on Earth was added equally to a pallet?
I understand that composition of minerals determines dirt color but what makes dirt its color is not the question I am asking.
Kata Tjuta, Northern Territory, Australia
Sagada, Mountain Province, Philippines
https://eugeneexplorer.wordpress.com/2016/11/22/blue-soil-hills/
Gentry County, Missouri, United States
http://www.airphotona.com/image.asp?imageid=11944 This gif, prepared by the United States Department of Agriculture - Natural Resources Conservation Services (USDA-NRCS) soil scientists at the National Soil Survey Center, has soil colors based on the Munsell Color System for the United States at different depths:
The soil colors nearest the surface are darker due to more organic matter and are lighter at depth with varying colors by region.
Source: http://munsell.com/color-blog/soil-colors-national-parks-anniversary/
This link also has soil colors of select United States National Parks. For example:
The following is multiple choice question (with options) to answer.
Where is pedocal soil commonly found? | [
"slopes",
"forests",
"grasslands",
"deserts"
] | C | Pedocal is the soil common in grasslands. The more arid climate increases calcium in the soil. Pedocal is not as fertile. |
SciQ | SciQ-4987 | human-biology, digestive-system, immune-system, microbiome
The next level of defense comes from the cells of the innate immune system (14). In innate immunity, specialized cells monitor the area they are in for Pathogen-Associated Molecular Patterns (PAMPs). PAMPs can be sugars that make up the cell walls of the microbe or proteins that get expressed on the surface of the organism, such as Flagellin, a protein only found in the flagella of certain pathogen. The innate immune cells have pattern recognition receptors (PRR) that have a general specificity for recognizing and responding to the PAMPs. Our cells even have PRRs for DNA and Double Stranded RNA's, however those are usually found in vesicles on the inside of the cell. These interactions are very general, however once PRRs bind to the PAMP, they are able to signal into the cytoplasm, which can lead to the production of proteins, among other possible responses.
Here you can think of PRRs like a motion detector in a security system; the dog, or your two year old, or an intruder are going to set off the alarm just the same. It is not specific. The motion sensor "knows" that something that it is supposed to recognize, i.e. a moving object larger than a mouse passed by and it triggered the response, but it cannot tell you which moving object triggered it, only that it was triggered.
The innate immune cells are also able to respond by "eating" the pathogen in a process called phagocytosis. Here, they break up the bacteria, yeast, or the remnants of other dead host cells or large pathogens, things like worms, and put the broken up pieces on protein molecules on their surface.
When innate immune cells do this, they are presenting molecules to specialized immune cells (adaptive immune cells (14)), B-Cells and T-Cells, that are highly specific as to what they will react to. These cells can also cause a lot of damage to the host, so they are tightly regulated. Think of the interactions as keys and locks. A protein from a bacteria should turn a few of these cells on, but a protein from the host should not fit the lock.
The following is multiple choice question (with options) to answer.
What are the key cells in the immune response? | [
"keratinocytes",
"erythrocytes",
"lymphocytes",
"leukocytes"
] | C | Lymphocytes are the key cells in the immune response. They are leukocytes that become activated by a particular antigen. There are two major type of lymphocytes: B cells and T cells. |
SciQ | SciQ-4988 | photosynthesis, chloroplasts
Title: Chloroplasts in an animal cell What would happen if we inject a chloroplast organelle into an animal cell?
Will the animal cell destroy it? Or is it possible that the chloroplast will somehow survive, and even replicate? Could there be photosynthesis in such a cell, or will some of the necessary mechanisms be missing? To answer your bigger question:
Yes, most of this is possible - under some conditions -, and animals and animal cells can acquire chloroplasts, and use them.
E.g.: see Elysia chlorotica whose cells actively take up chloroplasts and use them, and keep them alive (though not replicating). - Though some genes of algae are also contained in the Elysia chlorotica genome - which may be considered as partial replication.
Also there are salamanders that have replicating algae within them (since embryogenesis) - even algae (with chloroplasts) within animal cells - though here the algae might be rather understood as symbionts or "cell types", and the animal cells don't have the chloroplasts by themselves.
The following is multiple choice question (with options) to answer.
Where are most chloroplasts found in plants? | [
"leaves",
"flowers",
"roots",
"stems"
] | A | In plants, most chloroplasts are found in the leaves. Therefore, all the raw materials needed for photosynthesis must be present in the leaves. These materials include light, water, and carbon dioxide. The shape of the leaves gives them a lot of surface area to absorb light for photosynthesis. Roots take up water from the soil. Stems carry the water from the roots to the leaves. Carbon dioxide enters the leaves through tiny openings called stomata. (The oxygen released during photosynthesis also exits the leaves through the stomata. ). |
SciQ | SciQ-4989 | genetics, vision
Title: Color vision across species Is it true that color vision is sex-linked for all species with binary sexes? Is there an evolutionary significance to the fact that color vision is X-linked in humans? E.g., only female humans can be tetrachromats. Short answer
Human females do not benefit much from an extra cone class, as color discrimination is hardly affected in most tetrachromats. In fact, tetrachromats often show increased error rates in their color discrimination. In dichromatic New World monkeys the heterozygous females do functionally benefit from their extra cone as they gain trichromatic vision.
Background
Anomalous trichromats have all of their three cone types to perceive colors, but one type of cone perceives light slightly out of alignment. There are three different types of effect produced depending upon which cone type is affected.
The different anomalous conditions are protanomaly (reduced sensitivity to red light), deuteranomaly (reduced green sensitivity - the most common type) and tritanomaly (reduced blue sensitivity - extremely rare). People with deuteranomaly and protanomaly are collectively known as red-green colour blind and they generally have difficulty distinguishing between reds, greens, browns and oranges. They also commonly confuse different types of blue and purple hues. Red and green cones are indeed coded on the X-chromosome.
One source of variation is the very common Ser180Ala polymorphism that accounts for two spectrally different red pigments and that plays an important role in variation in normal color vision as well as defective color vision. The most common source of variation is the existence of several types of red/green pigment chimeras. The red and green-pigment genes are arranged in an array on the X-chromosome with one red-pigment gene followed by one or more green-pigment genes. Recombination events have given rise to red/green hybrid genes and deletion of the green-pigment genes. Only the first two genes in the tandem are expressed. The severity of red-green color vision defects is inversely proportional to the difference between the wavelengths of maximal absorption of the photopigments encoded by these two genes.
Females who are heterozygous for red and green pigment genes that encode three
The following is multiple choice question (with options) to answer.
What type of x-linked trait is color blindness? | [
"predominant",
"conscientiousness trait",
"recessive",
"dominant"
] | C | Pedigree for Color Blindness. Color blindness is an X-linked recessive trait. Mothers pass the recessive allele for the trait to their sons, who pass it to their daughters. |
SciQ | SciQ-4990 | organic-chemistry, reaction-mechanism
Title: Acetaldehyde with few drops of concentrated sulphuric acid
Acetaldehyde on treatment with a few drops of concentrated $\ce{H2SO4}$ gives?
Attempt:
First, I formed an enol intermediate in acidic medium $\ce{CH2=CHOH}$. Then, I performed electrophilic addition of another acetaldehyde molecule on this enol intermediate to get $\ce{CH3CH(OH)CH2CHO}$.
But answer given in my book is:
Please let me know the error in my attempt. You're not wrong.
Your mechanism describes the classic acid catalyzed synthesis of 3-hydroxybutanal by dimerisation of acetaldehyde (Borodin 1869, Wurtz 1872).
Image: Whoopie23, Wikipedia
However, under different conditions acetaldehyde forms different addion and condensation products. E.g. with concentrated sulphuric acid at low temperatures metaldehyde is formed whereas at room temperature paraldehyde (the answer given in your book) is formed.
The following is multiple choice question (with options) to answer.
What do you call a condensation reaction in which an ester is formed from an alcohol and a carboxylic acid? | [
"esterification",
"transesterification",
"esterisation",
"decarboxylation"
] | A | An esterification is a condensation reaction in which an ester is formed from an alcohol and a carboxylic acid. Esterification is a subcategory of condensation reactions because a water molecule is produced in the reaction. The reaction is catalyzed by a strong acid, usually sulfuric acid. When the carboxylic acid butanoic acid is heated with an excess of methanol and a few drops of sulfuric acid, the ester methyl butanoate is produced. Methyl butanoate has the scent of pineapples. The reaction is shown below with both molecular and structural formulas. |
SciQ | SciQ-4991 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
These types of cella support young, growing parts of a plant? | [
"epidermal cells",
"collenchyma cells",
"pinworm cells",
"angular cells"
] | B | |
SciQ | SciQ-4992 | energy, photons, semiconductor-physics, solar-cells
In down-conversion one high energy photon promotes an electron from 1 to 3, and by falling to energy level 2 and then 1, two photons can be emitted. Thus one high energy photon in and two low energy photons out.
Of course the next step would be to use a solar cell to collect the converted photons. The up and down converters themselves don't generate power.
Other approaches
There are other approaches to reaching higher efficiency. In specially engineered materials high energy photons can generate multiple electron-hole pairs which provides more current per photon than normal solar cells.
Then there are the hot-carrier approaches. If a material and maintain a thermal gradient then this provides an additional thermodynamic potential allowing higher efficiencies to be achieved.
You can even use hot-carrier materials as a spectral converters! I've worked on this approach over the last few years.
The following is multiple choice question (with options) to answer.
What can be used to convert the energy provided by the sun to usable electrical energy? | [
"Power Plants",
"Pannels",
"solar cells",
"Wind Mills"
] | C | Solar cells convert the energy in sunlight to electrical energy. They contain a material such as silicon that absorbs light energy and gives off electrons. |
SciQ | SciQ-4993 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
Most plant cells have a large central what? | [
"membranes",
"nuclei",
"vacuole",
"loci"
] | C | Most plant cells have a large central vacuole . It can make up as much as 90 percent of a plant cell’s total volume. The central vacuole is like a large storage container. It may store substances such as water, enzymes, and salts. It may have other roles as well. For example, the central vacuole helps stems and leaves hold their shape. It may also contain pigments that give flowers their colors. |
SciQ | SciQ-4994 | thermodynamics, heat-engine
You have your flame power the $`` {\small{\begin{array}{c} \textbf{Hot Water} \\[-25px] \textbf{/ Steam} \end{array}}} "$ stream. This step is how we input the excessive driving force that comes from the flame's unnecessarily high temperature.
You hook up some random waste heat source to the $`` {\small{\begin{array}{c} \textbf{Chilled} \\[-25px] \textbf{Water} \end{array}}} "$ stream. When the contents of this stream go through the $`` \textbf{Evaporator} " ,$ they'll give off their heat to evaporate the heat pump's internal working fluid – and, since the that internal working fluid is stealing the stream's thermal energy, that stream is cooled in the process. This step is where we get the extra thermal energy from.
You hook up whatever you want to heat, like the air to your home or the food you want to cook, to the $`` {\small{\begin{array}{c} \textbf{Cooling} \\[-25px] \textbf{Tower} \end{array}}} "$ stream. As the contents of that stream flow through the absorber, the internal working fluid is reconstituted in an exothermic reaction, warming the contents of the stream. The warmed stream then exits the heat pump, only to reenter it in the condenser. In the condenser, the gaseous internal working fluid condenses on the stream, again dumping heat into it (as condensation is also exothermic).
If you do a thermal-energy balance on the system, you'll see the the thermal energy from the flame and the waste-heat source both ended up warming your home/food/whatever. In effect, you got more thermal energy out of the flame than the flame actually had by using its excess driving force to also harvest thermal energy from a waste heat source.
possibility of a “reverse-refrigerator” that cooks?
The following is multiple choice question (with options) to answer.
When you heat a pot of water on a stove top, energy moves from the pot to its metal handle by what process? | [
"thermal radiation",
"convection",
"induction",
"conduction"
] | D | Sunlight is turned into electricity at a solar power plant. These power plants use a large group of mirrors to focus sunlight on one place. This place is called a receiver ( Figure below ). At the receiver, a liquid such as oil or water is heated to a high temperature. The liquid transfers its heat by conduction . In conduction, energy moves between two objects that are in contact. The higher temperature object transfers heat to the lower temperature object. For example, when you heat a pot of water on a stove top, energy moves from the pot to its metal handle by conduction. At a solar power plant, the energy conducted by the heated liquid is used to make electricity. |
SciQ | SciQ-4995 | metabolism, ecology, photosynthesis
Title: Why isn't phosphorus or nitrogen a limiting nutrient for animals? Nitrogen and Phosphorus are usually the limiting nutrient for plants, especially for algae. Phosphorus is used for DNA, ATP and phospholipids, and Nitrogen is used for pretty much every protein a cell might want to produce. That is, their need for biological processes is not tied specifically to photosynthesis: anything that lives is going to need them, pretty much for anything it might want to do. It would make sense for them to be a limiting nutrient for almost anything that's trying to grow, plant or animal.
Yet for animals the limiting "nutrient" seems to always be energy, ie: food. Why aren't animals limited by lack of nutrients in the same way that plants are? Obviously animals need these nutrients, too. Or to reverse the question, why do plants need so much more phosphorus/nitrogen than animals do?
My best guess is that an animal's digestion of plant material is relatively inefficient energy-wise but relatively efficient nutrient-wise. So for an animal to eat enough food to have sufficient energy to survive, it's probably eaten more than enough Nitrogen and Phosphorus for its needs. But I'm just guessing and I can't find any data that would back up that guess. Phosphorus
Your suggestion that if we are meeting our calorific requirement we will be getting enough is true for phosphorus.
Most foods contain lots of phosphorus. The maximum dietary requirement occurs during adolescent growth, estimated at 1250 mg per day. Assuming a calorie intake of 2500 kcal we can calculate a 2500 kcal equivalent phosphorus content for various foods:
skimmed milk contains 7,400 mg phosphorus per 2500 kcal
roasted chicken breast contains 7,500 mg phosphorus per 2500 kcal
cooked white rice contains 3840 mg per 2500 kcal
(Calculations are based upon values obtained via this site.)
Nitrogen
Our requirement for nitrogen is met by our protein intake: inadequate protein intake manifests as kwashiorkor which is essentially due to a dietary deficiency of essential amino acids. In other words, the only way to achieve a nitrogen-deficient diet is to not eat protein, and this would not be alleviated by any inorganic source of nitrogen, even if we could consume enough of such a N source.
The following is multiple choice question (with options) to answer.
Of all the mineral nutrients, what contributes the most to plant growth and crop yields? | [
"methane",
"silicon",
"nitrogen",
"oxygen"
] | C | |
SciQ | SciQ-4996 | reaction-mechanism, energy, theoretical-chemistry, reaction-coordinate
An approach towards identifying dynamic effect without trajectories
Insights into dynamic effects
Bifurcating organic reactions
The entirety of Chapter 8 of his book is also dedicated to this topic.
Addendum: FWIW, as a chemical engineer, the (imperfect) analogy that I like to use is to liken the MEP to the 'reversible process' of thermodynamics:
Start at the beginning state
Take an infinitesimal step
Let the system infinitesimally relax
Repeat 2 & 3 until you reach the end state
As I (very approximately) understand it, irreversibility comes from changing the state of a system "too much, too fast", leading to net generation of entropy as the system relaxes back to the reversible pathway, and it's "kinetic energy" in a qualitative, generalized sense that allows the system to depart from the reversible path.
The following is multiple choice question (with options) to answer.
What do you call a reaction that consumes energy as it is carried out? | [
"autotrophic",
"exothermic",
"endothermic",
"unstable"
] | C | The exothermic reaction on the left releases energy. The endothermic reaction on the right consumes energy. |
SciQ | SciQ-4997 | meteorology, atmosphere, carbon, co2, rain
Bear in mind that this assumes an enormous rainfall intensity, 100% CO2 saturation of the water and equilibrium chemical dynamics. After the raindrops hit the ground at least half of it will immediately re-evaporate back into the air, leaving, at absolute most, about 3% of the atmospheric CO2 leached out of the atmosphere that will be available to react with the soil, rock or biosphere. Also consider that this is but one of several important processes affecting CO2 transience, such as photosynthesis, respiration, volcanism, industrial pollution, etc. So the CO2 estimates that you read about are average values. Advection and turbulent air mixing should ensure that the CO2 regains approximately normal concentration within an hour or two after rainfall.
The following is multiple choice question (with options) to answer.
What type of rain dissolves and damages stone buildings and statues? | [
"acid rain",
"stored rain",
"morning rain",
"plastic rain"
] | A | A: Acid rain dissolves and damages stone buildings and statues. The Figure below shows a statue that has been damaged by acid rain. |
SciQ | SciQ-4998 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
What organ packages nutrients absorbed by the digestive system; produces plasma proteins, clotting factors, and bile; and disposes of worn-out cell components and waste products? | [
"liver",
"heart",
"liver",
"brain"
] | A | Hepatic Portal System The liver is a complex biochemical processing plant. It packages nutrients absorbed by the digestive system; produces plasma proteins, clotting factors, and bile; and disposes of worn-out cell components and waste products. Instead of entering the circulation directly, absorbed nutrients and certain wastes (for example, materials produced by the spleen) travel to the liver for processing. They do so via the hepatic portal system (Figure 20.43). Portal systems begin and end in capillaries. In this case, the initial capillaries from the stomach, small intestine, large intestine, and spleen lead to the hepatic portal vein and end in specialized capillaries within the liver, the hepatic sinusoids. You saw the only other portal system with the hypothalamic-hypophyseal portal vessel in the endocrine chapter. The hepatic portal system consists of the hepatic portal vein and the veins that drain into it. The hepatic portal vein itself is relatively short, beginning at the level of L2 with the confluence of the superior mesenteric and splenic veins. It also receives branches from the inferior mesenteric vein, plus the splenic veins and all their tributaries. The superior mesenteric vein receives blood from the small intestine, two-thirds of the large intestine, and the stomach. The inferior mesenteric vein drains the distal third of the large intestine, including the descending colon, the sigmoid colon, and the rectum. The splenic vein is formed from branches from the spleen, pancreas, and portions of the stomach, and the inferior mesenteric vein. After its formation, the hepatic portal vein also receives branches from the gastric veins of the stomach and cystic veins from the gall bladder. The hepatic portal vein delivers materials from these digestive and circulatory organs directly to the liver for processing. Because of the hepatic portal system, the liver receives its blood supply from two different sources: from normal systemic circulation via the hepatic artery and from the hepatic portal vein. The liver processes the blood from the portal system to remove certain wastes and excess nutrients, which are stored for later use. This processed blood, as well as the systemic blood that came from the hepatic artery, exits the liver via the right, left, and middle hepatic veins, and flows into the inferior vena cava. Overall systemic blood composition remains relatively stable, since the liver is able to metabolize the absorbed digestive components. |
SciQ | SciQ-4999 | newtonian-mechanics, forces, friction, free-body-diagram
Title: Implication of "gradually pulled\moved\pushed" in high school Newtonian physics In some of the physics problem I've been going over, the phrase "gradually pulled/moved/pushed" is coming up again. I can not understand what the implication of this is. Here is an example problem where it comes,
In the setup shown, a block is placed on a frictionless floor, the cord and pulleys are ideal and each spring has stifness $k$. The block is pulled away from the wall. How far will the block shift, while the pulling force is increased gradually from zero to a value $F$?
My concern what does the meaning of "gradual" in this case imply? Does the word play any vital role?
To be clear, I am not interested in the solution of above the problem, but rather what "gradually pulled" means in this post I think this remark is probably to avoid dealing with complications that arise if you were to not gradually exert a force. For instance, in real life if you yank on a box attached to a spring (the spring is attached to some wall as in your picture) and then hold the box with the same force you yanked it with, the spring will not just extend: it will wiggle and wobble and probably have some sort of wave motion going through it. In other words, the situation becomes more complicated. To avoid this potentially complicated spring behavior, we gradually increase the force exerted on the box.
It is the same general idea as the following. In some electricity and magnetism problems, we talk about "moving a charge such that the charge does not accelerate". We do not want the charge to accelerate because accelerating charges can introduce the complication of radiation.
The following is multiple choice question (with options) to answer.
What is defined as a push or pull acting on an object? | [
"force",
"work",
"effort",
"motion"
] | A | Force is defined as a push or pull acting on an object. Forces include gravity, friction, and applied force. |
SciQ | SciQ-5000 | gravity, earth, moon, celestial-mechanics
Title: Speed of the Moon Why the motion of the Moon looks very slow in the sky? Doesn't it need the high speed in order to escape the earth's gravity? The Moon moves at about a thousand metres per second, but it's a long way away so it only appears to move slowly. Most of the apparent movement of the Moon is actually due to the rotation of the Earth. We see it appearing to go round the Earth once a day, but it actually takes about 28 days to complete an orbit.
The Wikipedia article on the Moon's orbit has these and many other stats about the Moon.
The following is multiple choice question (with options) to answer.
How much time does the moon take to complete one revolution around the earth? | [
"one week",
"one day",
"one year",
"one month"
] | D | |
SciQ | SciQ-5001 | evolution, zoology, taxonomy, phylogenetics
The apomorphy that defines the tetrapods is "paired limbs". You have Amphibia to the left and Amniota to the right, whose apomorphy is " egg with extraembrionic membranes". Inside them, you have Reptilia, whose apomorphies are "skull with upper and lower fenestra and beta-keratin in epidermis". Turtles came from an ancestor with these characteristics. So, turtles belong to the monophyletic group of "Reptiles".
Post scriptum: You wrote that "turtles (specifically sea turtles) live on both land and water, very much like amphibians". Just a curiosity: the reason why sea turtles leave the water (sea) from time to time shows exactly that they are not amphibians! Amphibians, being non-amniotes, have eggs that survive under water (actually, with few exceptions, they need to be under water). Turtles, on the other hand, are amniotes, and the amniotic egg cannot be laid under water. That's why the turtles have to leave the water to lay eggs: because, contrary to the amphibians, they cannot lay eggs under water.
The following is multiple choice question (with options) to answer.
Like other amphibians, frogs generally lay their eggs in moist environments, which are required since the eggs lack what feature? | [
"shells",
"membrane",
"nucleus",
"tubes"
] | A | Frog eggs are fertilized externally, and like other amphibians, frogs generally lay their eggs in moist environments. A moist environment is required as eggs lack a shell and thus dehydrate quickly in dry environments. Frogs demonstrate a great diversity of parental behaviors, with some species laying many eggs and exhibiting little parental care, to species that carry eggs and tadpoles on their hind legs or backs. The life cycle of frogs, as other amphibians, consists of two distinct stages: the larval stage followed by metamorphosis to an adult stage. The larval stage of a frog, the tadpole, is often a filter-feeding herbivore. Tadpoles usually have gills, a lateral line system, long-finned tails, and lack limbs. At the end of the tadpole stage, frogs undergo metamorphosis into the adult form (Figure 29.18). During this stage, the gills, tail, and lateral line system disappear, and four limbs develop. The jaws become larger and are suited for carnivorous feeding, and the digestive system transforms into the typical short gut of a predator. An eardrum and air-breathing lungs also develop. These changes during metamorphosis allow the larvae to move onto land in the adult stage. |
SciQ | SciQ-5002 | v_s}$ $f_r=f_s\frac{v+v_r}{v+v_s}$ Given data are: f_s=480\ {\rm Hz} , v_r=\frac{1}{3}v_s , f_r=422\ {\rm Hz} $\Rightarrow 422=480\frac{345+\frac{1}{3}v_s}{345+v_s}$ $v_s=76.37\frac{{\rm m}}{{\rm s}}$ When a certain string is clamped at both ends, the lowest four resonant frequencies are 50,100,150, and 200 \mathrm {Hz}. When the string is also clamped at its midpoint, the lowest four resonant frequencies are: (a) 50, 100, 150, and 200 Hz (b) 50, 150, 250, and 300 Hz (c) 100, 200, 300, and 400 Hz (d) 25, 50 75, and 100 Hz (e) 75, 150, 225, and 300 Hz The waves which produced in a string with both ends fixed is called standing waves. In this case, the length of string is equal to some integer multiple of half-wavelengths i.e. L=n\ \lambda /2 or its wavelengths are quantized as {\lambda }_n=2L/n where {\lambda }_n is the wavelength of the nth mode.In the other words, a standing wave can exist only if its wavelength satisfies the equation above. The fundamental relation between frequency f and wavelength \lambda of a travelling wave with velocity v is v=f\lambda . Therefore, the frequency of nth mode is found as $f_n=n\frac{v}{2L}\ ,\ \ \left(n=1,2,3,\dots \right)$ The frequency of n=1 case is called the fundamental frequency i.e. f_1=v/2L. The 50\ \mathrm{Hz} frequency in above is fundamental frequency so using it we can find the ratio of v/L as $f_1=\frac{v}{2L}\to
The following is multiple choice question (with options) to answer.
What is the ratio of a wave frequency to its vibration frequency? | [
"one",
"same",
"three",
"two"
] | B | The frequency of a wave is the same as the frequency of the vibrations that caused the wave. For example, to generate a higher-frequency wave in a rope, you must move the rope up and down more quickly. This takes more energy, so a higher-frequency wave has more energy than a lower-frequency wave with the same amplitude. You can see examples of different frequencies in the Figure below (Amplitude is the distance that particles of the medium move when the energy of a wave passes through them. ). |
SciQ | SciQ-5003 | terminology, human-physiology, organs
Title: Medical term for "holding urine for a long time" Sometimes I get/feel pain in my stomach because of holding urine for long time. Is there any medical terminology describing: "holding urine for a long time", or pain associated with this activity? A swollen organ may be described as distended if the swelling is symptomatic of a medical disfunction.
The purpose of most bladders is to collect and retain a fluid; if that fluid needs to be discharged periodically, and is not able to do so, then there is usually pain as a result of the distension.
Inability to urinate is known as ischuria or urinary retention, and could be the result of obstruction to the urethra, could be a failure of the bladder to fully contract during urination, or could many other possible causes.
The following is multiple choice question (with options) to answer.
What is the hollow and muscular balloon-shaped organ that collects urine? | [
"urinary bladder",
"kidney",
"urethra",
"prostate"
] | A | The urinary bladder is a hollow and muscular organ. It is shaped a little like a balloon. It is the organ that collects urine. |
SciQ | SciQ-5004 | biochemistry, biophysics, bioenergetics
Title: Are there known life forms that are able to transform mechanical energy into chemical energy? Are there known life forms that are able to transform mechanical energy into chemical energy?
This question asks a similar subject, but more specific and has no answers.
The background of this question are thoughts about hypothetical life on tidally locked exoplanets of red dwarf stars, where light for photosynthesis is scarce but mechanical energy (storms and/or water currents) aplenty. There are no known life forms that use mechanical energy as a primary form of metabolic energy (i.e., for generic cellular functions). Many life forms are sensitive to mechanical disruption in some way, so they do utilize mechanical energy, but in a very limited fashion (@David's answer touches on this), and of course many organisms have life cycles that somehow depend on mechanical transportation (seed/spore dispersal, traveling on the wind or ocean currents, etc).
I think the main physical problem is that mechanical energy just isn't available to biological cells in a form that can be converted to substantial chemical energy. They are small, and tend to have other great benefits for being small.
To use an ocean wave as an example, there is very little or no perceptible movement for a cell in that wave, besides an apparent increase and decrease in the force of gravity. The top and bottom of the cell are moving together with the flow of water, so there is no differential to operate on.
An E. coli weighs about 1 picogram. If it could capture all of the energy from falling from 1km in the air on earth, assuming no uncaptured aerodynamic drag, that would be about 10-11 joules.
If there are ~3000 kJ/mol of energy available from burning glucose, that means about 5 × 10-21 joules per molecule of glucose, so about 20 billion glucose molecules, which sounds like a lot but it is only 1 femtogram, 0.1% the weight of the cell.
The following is multiple choice question (with options) to answer.
Sugars, starches, and cellulose are examples of what biochemical compounds that organisms use for energy? | [
"prokaryotes",
"carbohydrates",
"calories",
"proteins"
] | B | Carbohydrates are biochemical compounds that include sugars, starches, and cellulose. They contain oxygen in addition to carbon and hydrogen. Organisms use carbohydrates mainly for energy. |
SciQ | SciQ-5005 | embryology
Title: Is endoderm visible in the germ layer? This picture is my drawing about germ layer - not embryonic folding as I wrote initially.
Where exactly is the endoderm here in the picture?
The known things
Ectoderm
Neural tube
Notochord
Endoderm - Where is this?
Somite
Somite leg
Intraembryonic coelom
Embryonic somatopleura
Embryonic splanchopleura (lateral mesoderm)
Endoderm
Mesoderm (intraembryonic) I think you're going for a view of tube formation, in which case, here's a good image:
Lateral plate mesoderm
Intermediate mesoderm
Somite mesoderm
Chorda
Endoderm
(Reference)
Again in your drawing I think you correctly have it labeled as 10, and don't really need to put it twice.
The following is multiple choice question (with options) to answer.
During the embryonic stage of vertebrates, the notochord develops into what? | [
"backbone",
"brain stem",
"umbilical cord",
"rib cage"
] | A | Living chordates are mainly vertebrates. In vertebrates, the notochord develops into a backbone, or vertebral column, after the embryonic stage. A small percentage of chordates are invertebrates. Their notochord never develops into a backbone. Invertebrate chordates include tunicates and lancelets. Both groups of animals are small and relatively primitive. They are probably similar to the earliest chordates that evolved more than 500 million years ago. |
SciQ | SciQ-5006 | ros, rostopic, ros-indigo, joint-state
I know this is documented somewhere more officially - I'll try to get a link.
As gvdhoorn mentioned, I made a mistake here, either the gripper joints are there, or the other joints are there.
This is expected behavior. See this Wiki for the reference.
The following is multiple choice question (with options) to answer.
What category of joints is immovable? | [
"sporozoans",
"synarthrosis",
"diarthroses",
"amphiarthroses"
] | B | Classification of Joints on the Basis of Function The functional classification divides joints into three categories: synarthroses, amphiarthroses, and diarthroses. A synarthrosis is a joint that is immovable. This includes sutures, gomphoses, and synchondroses. Amphiarthroses are joints that allow slight movement, including syndesmoses and symphyses. Diarthroses are joints that allow for free movement of the joint, as in synovial joints. |
SciQ | SciQ-5007 | genetics, botany, twins
In a number of varieties, two and sometimes three megaspores were functional, giving rise to several embryo sacs. On fertilization, embryos develop in these, causing the phenomenon of pseudopolyembryony.
Therefore this source seems to agree with the first.
However, a more recent paper Martínez-Gómez, P., & Gradziel, T. M. (2003). Sexual polyembryony in almond. Sexual plant reproduction, 16(3), 135-139., focused on almonds, suggests that certain almond cultivars are prone to true polyembryony, though it seems like the additional seeds are often a bit stunted and have high mortality. They also reference a paper purporting to mention polyembryony in peach, Toyama, T. K. (1974). Haploidy in peach. HortScience, 9, 187-188., though I cannot find this article in anything but Japanese - the title, however, suggests that these may be haploid polyembryos, which also occur with the almonds - these are indeed from division of the same embryo, but because they are haploid they would not actually be genetically identical, since each is taking half of the diploid chromosomes.
With only these limited descriptions to go by, which seem to be mostly observational rather than backed by any systematic study, I would hesitantly conclude that most likely what you are seeing is a fruit in which two separate ovules developed together, and therefore could be as genetically different as any two different peaches from the same tree. True polyembryos seem to be possible in stone fruits, but as a mostly rare occurrence that is only common in particular strains - when it does occur, it may be via haploidy, which means the seeds will still be genetically distinct.
The following is multiple choice question (with options) to answer.
What do male cones in seed plants contain? | [
"nutrients",
"nitrogen",
"pollen",
"spores"
] | C | |
SciQ | SciQ-5008 | acid-base, corrosion
Title: Are all corrosives either acids or bases? Are all corrosives either acid or a base? From what I could remember from school, strong acids and bases can be corrosive, but can substances be corrosive from reasons other than that? I tried my best to check for the answer with my limited knowledge.
If it is not just acids and bases what is it then, how can we categorize them, if possible in simple terms? Wikipedia lists many corrosive compounds. While a lot of them function as strong acids or bases, there are also these (not an exhaustive list):
Strong oxidizers including concentrated hydrogen peroxide
Fluorides (they say "fluoride ion", so salts as well as the acid are meant)
Organic compounds that can act as alkylating agents such as methyl sulfate
The moral of the story: Hazards can't be pigeonholed into specific types of chemicals. Best to find and read the safety data sheet with any chemical.
The following is multiple choice question (with options) to answer.
What kind of harm does a corrosive substance cause? | [
"Attracts dust",
"Rust objects",
"Builds a crust",
"eats through objects"
] | D | If a substance is corrosive, it can eat through objects. Many scientists have to work with chemicals that are corrosive or otherwise dangerous. That's one reason that following safety precautions in the laboratory or field is very important. |
SciQ | SciQ-5009 | organic-chemistry, biochemistry, molecules
Title: Why might two different chemical structures smell the same? From what I understand, it is the functional group attached to a structure that determines the odor it will give off, for the most part. Which explains why two similar molecules, except for their functional groups, would smell different. So, would that make it so that two different molecules with the same functional groups would smell the same? The molecular determinants of odor perception is a disputed area in fragrance biochemistry. There are two basic theories: the "shape" hypothesis and the "vibrations" hypothesis. Luca Turin is the foremost exponent of the more controversial and less widespread "vibrations" hypothesis, but he does a good job of explaining both theories in his TED talk.
According to the vibrational theory, since different functional groups have different vibrational modes, they should smell quite different. An example from Luca's talk is a complex alcohol vs. the corresponding thiol.
According to the shape theory, molecules which have similar but not identical functional groups should smell similarly, unless the protein receptors in our nose that sense odors have very exquisite shape sensitivity, enough to perceive the very slight difference in the shape of thiol vs. an alcohol in a large otherwise identical molecule.
Why might two different chemical structures smell the same?
According to one theory, they would smell the same if they had similar vibrational (i.e. infrared) spectra. In 2011, PNAS published is a very intriguing result that showed this was true for fruit flies in the case of some odorants. They changed the vibrations by isotopic substitutions, a method that should leave essentially unchanged molecule's shape and its chemical reactivity.
So, would that make it so that two different molecules with the same functional groups would smell the same?
In my mind this is true if you believe the vibrational theory as well. But it is harder to understand why it is true if you believe the shape theory.
Of course, the real answer may be a combination of both theories. I'm a tepid supporter of the vibration theory myself, but I would be very interested in a chem.se answer from another expert who is less impressed with Dr. Turin's theories than me.
The following is multiple choice question (with options) to answer.
Receptors for what chemical messengers recognize molecules with specific shapes and side groups, and respond only to those that are recognized? | [
"enzymes",
"chromosomes",
"hormones",
"acids"
] | C | Pathways of Hormone Action The message a hormone sends is received by a hormone receptor, a protein located either inside the cell or within the cell membrane. The receptor will process the message by initiating other signaling events or cellular mechanisms that result in the target cell’s response. Hormone receptors recognize molecules with specific shapes and side groups, and respond only to those hormones that are recognized. The same type of receptor may be located on cells in different body tissues, and trigger somewhat different responses. Thus, the response triggered by a hormone depends not only on the hormone, but also on the target cell. Once the target cell receives the hormone signal, it can respond in a variety of ways. The response may include the stimulation of protein synthesis, activation or deactivation of enzymes, alteration in the permeability of the cell membrane, altered rates of mitosis and cell growth, and stimulation of the secretion of products. Moreover, a single hormone may be capable of inducing different responses in a given cell. |
SciQ | SciQ-5010 | thermodynamics, classical-mechanics, experimental-technique
Title: What special feature does this kind of coupling have? This diagram was in the 4th chapter of the book Heat and Thermodynamics, Zemansky and Dittman.
An amount of gas confined to a cylinder of thermally insulator material, here, is undergoing an adiabatic expansion. As the gas expands, the body is lifted.
My question is that why is the mechanism designed like that? I mean that almond shaped thing attached to the small gear. There must be an idea behind it, as the book says:
My own guess is that this kind of hanging the mass, guarantees a quasi-static process. As the piston moves up the pressure inside the cylinder decreases.
Thus the force exerted by the gas in the cylinder on the piston decreases.
What is needed to allow the piston to move up slowly is to apply a decreasing external force on the piston as the piston moves up such that the external force is slightly less than the force exerted by the gas on the piston.
That decreasing force is achieved using the cam, rack and pinion.
There is a lever with axle of the pinion/cam acting as the fulcrum.
As the rack moves up the cam rotates and reduces the distance between the line of action of the weight and the axle thus reducing the torque produced by the weight and hence the torque exerted by the pinion.
Hence the force on the rack/piston is reduced.
Update
Schematic diagram of apparatus
When the piston has moved a distance $x$ from the bottom of the cylinder the rack has also moved upwards a distance $x$.
At the same time the pinion and the cam have rotated through an angle $\theta$.
$x=a \theta$ where $a$ is the fixed radius of the pinion.
For an adiabatic expansion $PV^\gamma = {\rm constant} = \dfrac F A (Ax)^\gamma \Rightarrow F x^\gamma = \rm constant$
With the symbols as defined in the diagram $F = \dfrac b a mg \Rightarrow b\;\theta^\gamma = \rm constant$ and this is the equation for the shape of the cam.
The following is multiple choice question (with options) to answer.
A hydraulic jack that makes it possible to lift a car easily is an example of what, meaning it produces mechanical advantages? | [
"simple machine",
"complex machines",
"quantum physics",
"simple weapon"
] | A | A person is able to lift the entire rear end of the automobile using only one hand with the hydraulic jack shown in the image. Hydraulic systems are similar to simple machines in that they can produce very large mechanical advantages. |
SciQ | SciQ-5011 | evolution, life-history
Title: Has there been any observation of species adapting the evolution process? I am very interested in the evolution of the evolution process itself. There are of course a lot of things that influence how evolution will work, but for this question, I am interested in things that are only related to the evolution process. Examples could be increase chance of mutations in newborns, change in reproduction age, and similar. I am specifically interested in observation where the evolution process itself has adapted to a change in the environment. Bacteria such as E. coli are known to increase their mutation rate (by switching to a more error prone polymerase among other things) when under stress. This can mean being placed in a medium where it's not adapted to grow (http://www.micab.umn.edu/courses/8002/Rosenberg.pdf) or when treated with antibiotics (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1088971/?tool=pmcentrez).
The following is multiple choice question (with options) to answer.
What process consists of the mechanisms that produce an observed pattern of change? | [
"evolution",
"cycle",
"repetition",
"variation"
] | A | |
SciQ | SciQ-5012 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Prokaryotic cells have a cell wall located outside of the __________? | [
"plasma membrane",
"epidermis",
"chromosomes",
"chloroplasts"
] | A | Prokaryotic cells have a cell wall outside their plasma membrane. |
SciQ | SciQ-5013 | newtonian-mechanics, angular-momentum, rotational-dynamics
Title: Basic Understanding Of Angular Momentum I am trying to understand angular momentum in the same visceral way that I understand linear momentum, e.g., if someone rolls a bowling ball towards me then it is “natural” to me that I must apply a force to divert its path. It’s a little more mysterious that I encounter resistance when I apply torque to the axle of a spinning bicycle wheel.
If I imagine a point mass m rotating on a mass-less rod a distance r from its axis, I understand that I am to take the cross product of r and mv to get the angular momentum vector, but in my readings, this fact always seems to be presented without further explanation.
If I think about what’s going on with this system’s linear momentum, I would predict that it would wobble around as mv changed. In this case, when I apply torque, I think that I can see that I am trying to change mv and the resistance I would encounter is explainable in sort of the same way as the bowling ball above. Am I on the right track with this example? I note that if I add a second mass π radians from the first at the same distance, the linear momentum of the system disappears, but the angular momentum doubles. Should I explain that in this case that I should ignore the total momentum and that I am applying force separately to the 2 mvs? The dynamic properties of a spinning body can be understood in a visceral way, but not in the same way as for linear momentum.
In the case of linear momentum the principle one must have in mind first and foremost is the principle of relativity of inertial motion. When you take the case of an object in inertial motion you have the freedom to consider the motion of the object as seen from a co-moving point of view. You imagine yourself co-moving with that object.
In terms of this initially co-moving coordinate system the object is initially stationary. You can subsequently deliver an impulse to the object, and thus cause a velocity with respect to the initial coordinate system.
The principle of relativity of inertial motion gives that there is no inherent distinction between diverting the path of an object and accelerating from a standstill position. The two cases look different, but underneath they are one and the same case.
The following is multiple choice question (with options) to answer.
Multiplying the linear momentum of a spinning object by the radius calculates what? | [
"total momentum",
"angular torque",
"angular momentum",
"applied momentum"
] | C | The angular momentum of a spinning object can be found in two equivalent ways. Just like linear momentum, one way, shown in the first equation, is to multiply the moment of inertia, the rotational analog of mass, with the angular velocity. The other way is simply multiplying the linear momentum by the radius, as shown in the second equation. |
SciQ | SciQ-5014 | ph
Here, the addition of any $\ce{HA}$ will produce $\ce{H^+}$ and $\ce{A^-}$ in an aqueous solution (the blood), and decrease the $\ce{pH}$. $\ce{A^-}$ is only a base insomuch as it can form $\ce{HA}$ by combining with $\ce{H^+}$. This can occur if you add (or, as occurs in the kidney, reabsorb) $\ce{A^-}$ with some counter ion other than a proton. Then you can drive the equilibrium to to the left, towards $\ce{HA}$, decreasing $\ce{[H^+]}$. Otherwise, $\ce{A^-}$ derived from $\ce{HA}$ will not drive the equilibrium one way or the other. $\ce{H^+}$ will still dissociate as determined by the $\ce{K_a}$.
The following is multiple choice question (with options) to answer.
What are responsible for removing excess h+ ions from the blood? | [
"kidneys",
"liver nodes",
"intestinal walls",
"stomach chambers"
] | A | The kidneys are responsible for removing excess H+ ions from the blood. If the kidneys fail, what would happen to blood pH and to hemoglobin affinity for oxygen? Factors That Affect Oxygen Binding The oxygen-carrying capacity of hemoglobin determines how much oxygen is carried in the blood. In addition to P O , 2 other environmental factors and diseases can affect oxygen carrying capacity and delivery. Carbon dioxide levels, blood pH, and body temperature affect oxygen-carrying capacity (Figure 39.20). When carbon + dioxide is in the blood, it reacts with water to form bicarbonate (HCO− 3 ) and hydrogen ions (H ). As the level of carbon dioxide in the blood increases, more H+ is produced and the pH decreases. This increase in carbon dioxide and subsequent decrease in pH reduce the affinity of hemoglobin for oxygen. The oxygen dissociates from the Hb molecule, shifting the oxygen dissociation curve to the right. Therefore, more oxygen is needed to reach the same hemoglobin saturation level as when the pH was higher. A similar shift in the curve also results from an increase in body temperature. Increased temperature, such as from increased activity of skeletal muscle, causes the affinity of hemoglobin for oxygen to be reduced. Diseases like sickle cell anemia and thalassemia decrease the blood’s ability to deliver oxygen to tissues and its oxygencarrying capacity. In sickle cell anemia, the shape of the red blood cell is crescent-shaped, elongated, and stiffened, reducing its ability to deliver oxygen (Figure 39.21). In this form, red blood cells cannot pass through the capillaries. This is painful when it occurs. Thalassemia is a rare genetic disease caused by a defect in either the alpha or the beta subunit of Hb. Patients with thalassemia produce a high number of red blood cells, but these cells have lower-than-normal levels of hemoglobin. Therefore, the oxygen-carrying capacity is diminished. |
SciQ | SciQ-5015 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
What makes up the dense outer layer of bones? | [
"cartilage",
"scales",
"marrow",
"compact bone"
] | D | Compact bone makes up the dense outer layer of bones. |
SciQ | SciQ-5016 | inorganic-chemistry, alloy
Title: If alloys are homogeneous mixtures, why can't we separate their components? An alloy is a material composed of two or more metals or a metal and a nonmetal. And, they are usually formed by heating the elements to their melting points, and then cooling them, so that the components mix. Now, why doesn't this works backwards i.e. if we heat the alloy again to melting point of their constituents, and they should separate? Once the alloy has been formed the atoms from the different metals will have shared there electrons with each other and come to an equilibrium. In this state the metal atoms have formed a complex structure which has a different reactivity or properties than each individual metal did in its original form .
The following is multiple choice question (with options) to answer.
What refers to a substance made from two or more elements joined by chemical bonds? | [
"component",
"compound",
"contrast",
"basic"
] | B | In nature, elements rarely occur alone. Instead, they combine to form compounds. A compound is a substance composed of two or more elements joined by chemical bonds. For example, the compound glucose is an important body fuel. It is always composed of the same three elements: carbon, hydrogen, and oxygen. Moreover, the elements that make up any given compound always occur in the same relative amounts. In glucose, there are always six carbon and six oxygen units for every twelve hydrogen units. But what, exactly, are these “units” of elements?. |
SciQ | SciQ-5017 | pressure, friction, material-science
Now we have a triaxial compressive stress state. If all stresses were equal, there would be no plastic deformation. But as the friction forces have a limit, the vertical stress increases until the difference to the horizontal stress is enough to deform the material (or break the roll...). That is the reason for the friction hill.
The following is multiple choice question (with options) to answer.
Stress building up at the same rate over time at a fault causes what phenomenon? | [
"earthquakes",
"erosion",
"volcanoes",
"storms"
] | A | When an earthquake will occur is much more difficult to predict. Stress on a fault builds up at the same rate over time. So earthquakes should occur at regular intervals. But, so far, scientists cannot predict when quakes will occur even to within a few years. Around Parkfield, California, an earthquake of magnitude 6.0 or higher occurs about every 22 years. So seismologists predicted that one would strike in 1993. But that quake came in 2004—11 years late ( Figure below ). |
SciQ | SciQ-5018 | everyday-chemistry
Title: what's the difference between sand and quartz? What's the difference between sand and quartz?
Is quartz more crystalline form of sand? Do they have the same composition or my be not? or my be the two words is similar? Do they contain more than silica?
Thanks.
Sand is a poorly-defined mixture, not a necessarily a pure substance. Some sands are fairly pure $\ce{SiO2}$, the same chemical formula as pure quartz, but in some areas of the world, sand can be made of entirely different chemicals, such as calcite.
Quartz is a particular crystal form of $\ce{SiO2}$, but $\ce{SiO2}$ also forms the minerals tridymite, cristobalite, coesite, and stishovite, amorphous silica, etc. It's like having a collection of Legos or TinkerToys that have the same pieces, but can be assembled in different formats.
The following is multiple choice question (with options) to answer.
Materials made from non-living substances like pebbles and sand are called what? | [
"microscopic",
"fibrous",
"organic",
"inorganic"
] | D | Some of them are inorganic . Inorganic materials are made from non-living substances like pebbles and sand. |
SciQ | SciQ-5019 | atmospheric-science, density, air
Title: Why does the composition of the air does not change with altitude? Air contains about 78% nitrogen and 21% oxygen independent of altitude (up to 100 km). Why is this? Shouldn't the concentration of nitrogen increase with higher altitudes since nitrogen has a lower density than oxygen?
Shouldn't the concentration of nitrogen increase with higher altitudes since nitrogen has a lower density than oxygen?
No, it shouldn't, at least not up to 100 km or so. Look at your graph, which shows that even argon is well-mixed throughout the lower atmosphere (the troposphere, stratosphere, and mesosphere). Argon atoms are considerably more massive than are carbon dioxide molecules, which in turn are considerably more massive than oxygen and nitrogen molecules, and yet all of these (along with all of the long-lived gases in the atmosphere) are well-mixed throughout the lower atmosphere.
The reason is that the lower atmosphere is dense enough to support turbulence while the upper atmosphere is not. The turbopause marks the somewhat fuzzy boundary below which turbulent mixing dominates over diffusion and above which it's diffusion that dominates.
The following is multiple choice question (with options) to answer.
What type of gas levels in the atmosphere are increasing? | [
"helium gas",
"greenhouse gas",
"hydrogen gas",
"carbonate gas"
] | B | Greenhouse gas levels in the atmosphere are increasing. Global temperatures are increasing. |
SciQ | SciQ-5020 | geology, crust, geobiology
Title: Does crustal thickness have anything to do with how life existed and sustained on Earth? The original question that was put on hold "If the crust were the thickest layer of Earth, what effect would its thickness have on organisms?" was actually one of those 'counterfactual question' found on my science book, and it was really just a 'reflect upon' question. And it's actually a hard one for me to answer since it's 'what if?'s. So by revising, it would still confuse some poeple, but I guess it's already specific on its own. But I still find it hard.
Follow up question:
And what if it ever was thicker than the mantle or the rest of Earth's layers, can the planet still sustain biological life? If the crust were the thickest layer or Earth, several things would happen:
It wouldn't be a "crust" any more, by definition. Because this is what a "crust" is: a thin layer on the exterior of something. However, if we assume that the mechanical properties of the crust (being cold and brittle etc) would extend deeper in the Earth, the following applies.
No mantle convection, or at least mantle convection weak enough to probably not affect the surface. Therefore, no volcanoes, no mountain building, no subduction, no recycling of volatile elements, no sub-seafloor hydrothermal vents.
If it's cold enough, the core probably solidified and there is no magnetic field.
A good example would be Mars. A planet hypothesised to have tectonic activity in the past, but not any more. The crust of Mars isn't the thickest layer (again - think of definitions), but it is thicker in absolute and relative terms when compared to Earth. I will leave the implications of "Marsifying" Earth on organisms for you to figure out.
The following is multiple choice question (with options) to answer.
What is the earths crust composed of? | [
"sedimentary rock",
"igneuos rock",
"bicellular rock",
"metamorphic rock"
] | B | Like Earth, the Moon has a distinct crust, mantle, and core. The crust is composed of igneous rock. This rock is rich in the elements oxygen, silicon, magnesium, and aluminum. On the near side, the Moon’s crust is about 30 kilometers thick. On the far side, the crust is about 100 kilometers thick. The mantle is made of rock like Earth’s upper mantle. The Moon has a small metallic core, perhaps 300 to 500 kilometers in diameter. The composition of the core is probably mostly iron with some sulfur and nickel. We learned this both from the rock samples gathered by astronauts and from spacecraft sent to the Moon. |
SciQ | SciQ-5021 | cancer, mutations
Here is another great paper that specifically addresses your question, linking increased cell division with the accumulation of both significant and insignificant mutations, which over time, lead to an accumulation of mutations needed for cancer to develop.
The following is multiple choice question (with options) to answer.
Cells that are divided by oncogenes contain damaged what? | [
"dna",
"bacteria",
"atoms",
"cells"
] | A | Proto-oncogenes normally help control cell division. Mutations in these genes turn them into oncogenes. Oncogenes promote the division of cells with damaged DNA. |
SciQ | SciQ-5022 | genetics
Title: How does chromosome cross-over occur? I have heard that during meiosis, homologous chromosomes from each parent "cross-over", which enables the off-spring to inherit some alleles from the mother and some alleles from the father. The picture below illustrates this "cross-over", but of course this must occur at multiple sites, rather than just the one shown in the picture.
Now my question is what causes the chromosomes to align perfectly during cross-over so that the loci of a particular gene will substitute for the corresponding loci on the homologous chromosome, as opposed to being substituted with a completely random locus? Does each gene have a unique non coding sequence before it specifying what gene it is to enable this process to occur? Quite simply, because chromosome pairing is sequence specific. Holliday Junctions, which are the functional structures of a cross-over, occur through a process called "strand invasion," during which a region of one chromosome physically base-pairs with that of another. Thus one locus cannot pair with a random locus, as there is generally insufficient sequence complimentarity between two random regions to form a functional Holliday Junction. One interesting consequence of this mechanism is gene duplication and deletion in repetitious regions of the chromosome. For example, genes with large repeated regions, such as the gene responsible for Huntington's disease, can expand and contract during homologous recombination due to strand invasion occurring at non-equivalent, but still homologous, sites. Wikipedia does a nice job going over homologous recombination. I also recommend looking over the relevant sections in Molecular Biology of the Cell, available on the PubMed Bookshelf.
The following is multiple choice question (with options) to answer.
When does exchange of dna segments happen between non-sister chromatids of homologous chromosomes? | [
"during mitosis",
"during diversion",
"during meiosis",
"during crossing-over"
] | D | During crossing-over, segments of DNA are exchanged between non-sister chromatids of homologous chromosomes. Notice how this can result in an allele (A) on one chromosome being moved to the other chromosome. The four chromatids compose the tetrad, with a chiasma at the point of exchange. |
SciQ | SciQ-5023 | star, night-sky
Title: What is this rapidly twinkling red, blue, and white star I saw? Last night, I was on my balcony at 1AM (PST) and I looked up and saw two stars near the horizon (I'd guess ~30 degrees above the horizon), and they were "twinkling" about twice as fast as other stars higher in the sky, and I could clearly see them changing from red to white to blue repeatedly. Other stars in the sky only appeared white to me, and didn't seem to "twinkle" as rapidly as these two stars did. The red and blue make me think of red-shift and blue-shift, but I don't know how I would see both from the same object.
What was I seeing?
I don't know if it helps, but I am in the Los Angeles area, and I was looking in a roughly north direction. almost exactly to the east, according to google maps.
Edit: I tried taking a picture, but light pollution from the nearby street lights wouldn't permit me taking a decent picture. However, I noticed a group of three stars close together in nearly a perfect almost vertical line, and managed to find that in Stellarium. I think I found the two stars I am seeing: Procyon and Sirius
Is there anything about either of these stars that would make them show as red/blue? It's most probably Sirius. At this time of year (at 1 am local time) it's low in the sky in the East, so there is a lot of atmosphere in the way, and as Sirius is a bright bluish star, it will show all the colours described as it twinkles.
The following is multiple choice question (with options) to answer.
What are observable patterns of stars found in the night sky called? | [
"deformations",
"latitudes",
"deviations",
"constellations"
] | D | Humans have been studying the night sky for thousands of years. Knowing the motions of stars helped people keep track of seasons. With this information they could know when to plant crops. Stars were so important that the patterns they made in the sky were named. These patterns are called constellations . Even now, constellations help astronomers know where they are looking in the night sky. |
SciQ | SciQ-5024 | blood-circulation, kidney
Title: Why does glomerulus don't allow white blood cells to leave? The glomerulus in nephrons are just a ball of capillaries, so why can't it allow the white blood cells to squeeze though the epithelial cells into Bowman's capsule just like the formation of tissue fluid in other capillaries by filtration? Red blood cells, White blood cells, platelets and proteins with large molecular weight cannot pass through the podocyte and fenestrations in glomerular capillary, but small molecules like water, salts and sugars are filtered out as part of urine.
As these cells and proteins are large to cross through this filter, they remain in the capillary and create osmotic pressure within the capillary. Bowman’s space has osmotic pressure approximately zero. So, only hydrostatic pressure works in this state and help in movement of fluid across the capillary wall.
Via: https://opentextbc.ca/anatomyandphysiology/chapter/25-5-physiology-of-urine-formation/
The following is multiple choice question (with options) to answer.
If you were to filter out all the cells in blood, you would be left with what golden-yellow liquid? | [
"plasma",
"pus",
"hemoglobin",
"platelets"
] | A | If you were to filter out all the cells in blood, a golden-yellow liquid would be left behind. Plasma is this fluid part of the blood. Plasma is about 90% water and about 10% dissolved proteins, glucose, ions, hormones, and gases. Blood is made up mostly of plasma. |
SciQ | SciQ-5025 | organic-chemistry, redox
$$\ce{Zn^2+ + 2e- <=> Zn(Hg)} \quad E^\circ = \pu{−0.7628 V}$$
Many commonly used reducing agents in organic chemistry, such as $\ce{LiAlH4}$ and $\ce{NaBH4}$, serve as sources of the hydride ion $\ce{H-}$. As an example, in the reduction of ketones using $\ce{NaBH4},$ hydrogen is added across the $\ce{C=O}$ double bond though a tetrahedral intermediate.
The following is multiple choice question (with options) to answer.
The simplest organic compounds have hydrogen and what else? | [
"sodium",
"nitrogen",
"carbon",
"oxygen"
] | C | The simplest organic compounds are those composed of only two elements: carbon and hydrogen. These compounds are called hydrocarbons. Hydrocarbons themselves are separated into two types: aliphatic hydrocarbons and aromatic hydrocarbons. Aliphatic hydrocarbons are hydrocarbons based on chains of C atoms. There are three types of aliphatic hydrocarbons. Alkanes are aliphatic hydrocarbons with only single covalent bonds. Alkenes are hydrocarbons that contain at least one C–C double bond, and alkynes are hydrocarbons that contain a C–C triple bond. Occasionally, we find an aliphatic hydrocarbon with a ring of C atoms; these hydrocarbons are calledcycloalkanes (or cycloalkenes or cycloalkynes). Aromatic hydrocarbons have a special six-carbon ring called a benzene ring. Electrons in the benzene ring have special energetic properties that give benzene physical and chemical properties that are markedly different from alkanes. Originally, the term aromatic was used to describe this class of compounds because they were particularly fragrant. However, in modern chemistry the term aromatic denotes the presence of a six-membered ring that imparts different and unique properties to a molecule. The simplest alkanes have their C atoms bonded in a straight chain; these are callednormal alkanes. They are named according to the number of C atoms in the chain. The smallest alkane is methane:. |
SciQ | SciQ-5026 | organic-chemistry, thermodynamics, kinetics
...we see that for $k_2$ to be higher than $k_1$, i.e. for $\ln{\frac{k_2}{k_1}}$ to be greater than 0, then $\Delta G^{\ddagger}_2$ must be smaller than $\Delta G^{\ddagger}_1$ (note the negative sign).
The effect of temperature is still in the equation:
$$\ln{\frac{k_2}{k_1}} = -\frac{1}{RT}\left(\Delta G^{\ddagger}_2 - \Delta G^{\ddagger}_1 \right)$$
The assumption of TST is that $\Delta G^{\ddagger}$ is not a function of temperature. As temperature is lowered, then the $RT$ divisor in the equation gets smaller, which means that the difference $\left(\Delta G^{\ddagger}_2 - \Delta G^{\ddagger}_1 \right)$ affects the ratio of rate constants more. Thus, under the assumptions we have made, cooling will favor the kinetic product more. As temperature is raised, eventually $RT$ becomes much greater than $\left(\Delta G^{\ddagger}_2 - \Delta G^{\ddagger}_1 \right)$, so selectivity for the kinetic product vanishes because $\ln{\frac{k_2}{k_1}} \rightarrow 0$, i.e. $\frac{k_2}{k_1} \rightarrow 1$.
The following is multiple choice question (with options) to answer.
Temperature and what other environmental factor are important in the activity of an enzyme? | [
"ph level",
"size",
"shape",
"color"
] | A | |
SciQ | SciQ-5027 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
What glands are wedges of glandular and neuroendocrine tissue adhering to the top of the kidneys by a fibrous capsule? | [
"heart glands",
"nutrients glands",
"fatty glands",
"adrenal glands"
] | D | 17.6 | The Adrenal Glands By the end of this section, you will be able to: • Describe the location and structure of the adrenal glands • Identify the hormones produced by the adrenal cortex and adrenal medulla, and summarize their target cells and effects The adrenal glands are wedges of glandular and neuroendocrine tissue adhering to the top of the kidneys by a fibrous capsule (Figure 17.17). The adrenal glands have a rich blood supply and experience one of the highest rates of blood flow in the body. They are served by several arteries branching off the aorta, including the suprarenal and renal arteries. Blood flows to each adrenal gland at the adrenal cortex and then drains into the adrenal medulla. Adrenal hormones are released into the circulation via the left and right suprarenal veins. |
SciQ | SciQ-5028 | newtonian-mechanics, forces, newtonian-gravity, free-body-diagram, string
Title: How does a weight connected to a string over a pulley pulling a cart apply force onto the cart? How does the mass hanging down on the bottom (Assuming frictionless environment) apply a pull force to the car? How does the weight of the object transfer to the string (tension force and maybe the pulley does something?) which pulls the car? I wonder if the following diagram is helpful:
There is a force from the pulley on the string - that is what allows the tension to "turn the corner" so the force from the weight (which is downwards) is turned into a horizontal force (tension that can pull the cart).
The following is multiple choice question (with options) to answer.
What is the force that pulls downward on an object and is measured by weight? | [
"work",
"strength",
"gravity",
"light"
] | C | Weight measures the force of gravity pulling downward on an object. The SI unit for weight, like other forces, is the Newton (N). On Earth, a mass of 1 kilogram has a weight of about 10 Newtons because of the pull of Earth’s gravity. On the moon, which has less gravity, the same mass would weigh less. Weight is measured with a scale, like the spring scale shown in the Figure below . The scale measures the force with which gravity pulls an object downward. To delve a little deeper into weight and gravity, watch this video:. |
SciQ | SciQ-5029 | genetics, botany, seeds
Title: What DNA does a self-fertile plant's seedling have? Some plants are said to be self-fertile. An example is Prunus tomentosa.
Assuming that no cross-pollination happened with other plants, if a self-fertile plant such as prunus tomentosa produces a seedling, what DNA will the seedling have? Is the seedling's DNA an exact copy of the parent plant's DNA, or do the genes get rearranged? Selfing (aka self-fertilizing) differs from cloning. When selfing occurs, the offspring is not an exact copy of the parent. When cloning occurs, the offspring is an exact copy (except for a few mutations) of the parent.
Selfing implies that an individual will produce two gametes (typically a spermatozoid and an ovule but that might be a bit more complicated) and these two gametes are fusing to give the zygote (egg or offspring if you prefer).
As a consequence, when selfing, meiosis is occurring (and therefore segregation and recombination) so that the offspring is not an exact clone of the parent but rather some kind of a rearrangement of the parent genome (with a few mutations of course).
The following is multiple choice question (with options) to answer.
Which reproduction produces offspring genetically identical to the one parent? | [
"asexual",
"microscopic",
"sexual",
"bsexual"
] | A | That is the main difference between sexual and asexual reproduction. Sexual reproduction just means combining genetic material from two parents. Asexual reproduction produces offspring genetically identical to the one parent. |
SciQ | SciQ-5030 | quantum-mechanics, water, liquid-state
Title: Quantum description of water It seems that we have quantum description of solid and gas, but there seem to be few quantum models of liquid, with the exception of Liquid Helium or perhaps Fermi Liquid.
For solids, we often study crystal, which is easier due to the lattice symmetry. For gas, particles often interact weakly so it's easy to formulate a non-interacting model. In this sense, I can see why people choose to study these systems first.
But are there any models that make use of quantum mechanics to explore the liquid phase? Perhaps a quantum mechanical description of water.
Maybe we can combine Shrodinger Equation and Navier Stokes equation in some way. Of course Navier Stokes equation itself is already hard enough, so perhaps we need to go to certain limits. Fermi liquid, Luttinger liquid, Bose-Einstein condensate, Superconductivity and similar states of matter are known as quantum fluids or quantum liquids, and there are books written on the subject, see, e.g., Interactions in quantum fluids. The word liquid/fluid is however somewhat ambiguous, as it may mean different (although not mutually exclusive) things:
The following is multiple choice question (with options) to answer.
Water in its solid state is commonly known as what? | [
"sea",
"ice",
"carbon dioxide",
"glass"
] | B | During the water cycle, water occurs in three different states: gas (water vapor), liquid (water), and solid (ice). Many processes are involved as water changes state in the water cycle. |
SciQ | SciQ-5031 | oxygen, nitrogen
Thus, we need to add $\pu{112.6 m^3}$ of nitrogen to reach 5% concentration of oxygen. The answer seems reasonable because we need to add approximately 4 times of the original volume in order to lower the concentration 4 times.
The following is multiple choice question (with options) to answer.
Besides the concentration of dissolve oxygen and nutrients in the water, what other factor limits aquatic organisms? | [
"lake size",
"availability of sunlight",
"rainfall",
"temperature"
] | B | Most aquatic organisms do not have to deal with extremes of temperature or moisture. Instead, their main limiting factors are the availability of sunlight and the concentration of dissolved oxygen and nutrients in the water. |
SciQ | SciQ-5032 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Which type of membrane are ribosomes surrounded by? | [
"none",
"permenant",
"partial",
"temporary"
] | A | Ribosomes are found in both eukaryotic and prokaryotic cells. Ribosomes are not surrounded by a membrane. The other organelles found in eukaryotic cells are surrounded by a membrane. |
SciQ | SciQ-5033 | evolution, zoology, literature
Title: Which Darwin book (and today edition) is illustrated by his own drawings? I am interested in buying Charles Darwin books and mostly drawings (nowadays editions, I am not a collector). Please, can you advise in which book and which edition I can find the most of his drawings? I found some books as On the Origin of Species ad the Geology of The Voyage of The Beagle but I am not sure if there are his drawings too. I am a student so I couldn't spend too much money on it, but I was interested in his texts and drawings, supporting each other in one book/journal/publication. Thank you ! I believe that there is only one drawing in the first edition of On the Origin of Species, and it is Darwin's. Any good edition such as the fascimile edition with an introduction by Ernst Mayr, will include this drawing. I'm not sure about other editions of the Origin or other books of Darwin's. However, maybe you don't need to buy anything. Darwin Online is a wonderful collection that includes many (all?) of Darwin's writings over the years, including images of many of them; the drawings are no doubt included.
It's possible that the History of Science and Mathematics StackExchange site would be a better place for this question.
The following is multiple choice question (with options) to answer.
Which scientist was responsible for the theory of evolution by natural selection? | [
"stephen hawking",
"charles darwin",
"galileo Galilei",
"albert einstein"
] | B | Linnaeus classified organisms based on obvious physical traits. Basically, organisms were grouped together if they looked alike. After Darwin published his theory of evolution in the 1800s (discussed in the following chapter), scientists looked for a way to classify organisms that showed phylogeny. Phylogeny is the evolutionary history of a group of related organisms. It is represented by a phylogenetic tree , like the one in Figure below . |
SciQ | SciQ-5034 | botany, plant-physiology, fruit
Title: How does coconut water solidify into hardened coconut meat? At first, the coconut is filled with liquid endosperm. Later when it ripens, the outer layers form brown fibrous covering, and the inner solid layer turns brown and hardens. Within that, a white layer forms (which is soft and thin at first and then gradually hardens and thickens). After ripening, there is a white layer with very little fluid. So, it's gotta be the liquid endosperm which has hardened over the course of time to form the white layer. So, how does it harden? There are three types of endosperms encountered in botany - nuclear, heliobial and cellular. The endosperm of Cocos nucifera is both special and interesting.
Initially, the cocunut is a nuclear liquid endosperm. Meaning, it is a coenocytic liquid tissue with lots of rapidly dividing nuclei. The reference I cite here (although pretty old), states that it is safe to assume the fluid to be the 'sol' phase of cytoplasm. At some point, gelification of the sol surrounding the nuclei occurs and cellular boundaries start to appear.
These cells and nuclei start to settle down on the endothelium (inner lining of the integuments) and the cells divide to produce a columnar sort of a covering over the it. This is what forms the characteristic coconut meat. Development of the cellular endosperm is by coalescence of these deposited cells and nuclei at the antipodal end (bottom end of the fruit) and continues towards the top end. You might have noticed that the meat is thicker at the bottom but thins out towards the top.
The cells right above the endothelium stay meristematic for a long time while the columnar cells on top of this meristematic layer grow radially inward.
The following is multiple choice question (with options) to answer.
Soft cartilage gradually turns into hard bone through what process? | [
"oxidation",
"elongation",
"ossification",
"calcification"
] | C | Early in the development of a human fetus, the skeleton is made entirely of cartilage . The relatively soft cartilage gradually turns into hard bone through ossification . This is a process in which mineral deposits replace cartilage. As shown in Figure below , ossification of long bones, which are found in the arms and legs, begins at the center of the bones and continues toward the ends. By birth, several areas of cartilage remain in the skeleton, including growth plates at the ends of the long bones. This cartilage grows as the long bones grow, so the bones can keep increasing in length during childhood. |
SciQ | SciQ-5035 | biochemistry, fermentation
Title: Acetone–butanol–ethanol fermentation
Source
Source
Source
Acetoacetyl-CoA is a C3 unit.
3-Hydroxybutyryl-CoA / Butyryl is a C4 unit.
Where does the additional C atom come from? I'm suspecting it's another Acetyl-CoA -> CoA reaction, but I don't see it in the images. Well, I’m not sure I should answer this, as your question is predicated by an incorrect supposition:
Acetoacetyl-CoA is a C3 unit.
3-Hydroxybutyryl-CoA / Butyryl is a C4 unit.
Not according to Kegg:
However, my answer is worthwhile if I explain how I found this out. One way to check this sort of thing is to go to the Kegg website and search for the compounds of interest, find the appropriate pathway (shown below) and then click to check compounds and reactions.
There is also the Metacyc website for metabolic pathways, and you can check the formulae on Wikipedia.
The following is multiple choice question (with options) to answer.
Glycerol is a triol, an alcohol which contains three what? | [
"stark functional groups",
"cytoplasm functional groups",
"hydroxl functional groups",
"hydroxl acidic groups"
] | C | Glycerol is a triol, an alcohol which contains three hydroxyl functional groups. A fatty acid is a long carbon chain, generally from 12 to 24 carbons in length, with an attached carboxyl group. Each of the three fatty acid molecules undergoes an esterification with one of the hydroxyl groups of the glycerol molecule. The result is a large triester molecule referred to as a triglyceride. |
SciQ | SciQ-5036 | neuroscience, neurophysiology, hearing, human-ear, senses
Title: Depolarization and hyperpolarization in stereocilia of the inner ear It’s a well mentioned fact that when the stereocilia of the cochlear hair cells bend in one direction, the hair cell depolarizes, and when the stereocilia bend in the other direction, the cell hyperpolarizes. When the basilar membrane vibrates, the stereocilia are bent back and forth, creating depolarizations in the hair cells followed by hyperpolarizations. What I’m having trouble understanding is why this is significant. This does not determine the frequency of the sound wave, as that is determined by the location along the basilar membrane that the wave impinges on. I don’t see how this would determine amplitude either, seeing as a greater amplitude would only create more drastic bending of a greater number of hair cells. Can anyone shed some light on this? There are roughly two modes of pitch coding in the cochlea: place-coding and temporal coding. The place-theory is the most prevalent accepted model of how the cochlea realizes pitch coding (e.g., Zwislocki, 1991). Basically, it is based on a frequency-to-place Fourier transformation on the incoming sound, where each frequency is coded on a different place on the basilar membrane, as described accurately in the question.
However, there is another, much overlooked way of coding pitch, namely temporal coding. Up until about 1 kHz, spiral ganglion cells in the auditory nerve and acoustical brain stem regions (such as the inferior colliculus) have been found to respond in a phase-locked pattern (Du et al., 2011). Electrophysiology in auditory nerve fibers illustrates the phase-locked activity in response to low-frequency sounds (Fig. 1). This phase-locking behavior of neurons in the auditory system is called the frequency-following response (FFR).
The following is multiple choice question (with options) to answer.
The parts of the ears involved in balance are called what? | [
"symmetrical canals",
"semicircular canals",
"lobe canal",
"rectangular canals"
] | B | The parts of the ears involved in balance are the semicircular canals . Above, the semicircular canals are colored purple ( Figure above ). The canals contain liquid and are like the bottle of water pictured below ( Figure below ). When the bottle tips, the water surface moves up and down the sides of the bottle. When the body tips, the liquid in the semicircular canals moves up and down the sides of the canals. Tiny hair cells line the semicircular canals. Movement of the liquid inside the canals causes the hair cells to send nerve impulses. The nerve impulses travel to the cerebellum in the brain along the vestibular nerve. In response, the cerebellum sends commands to muscles to contract or relax so that the body stays balanced. |
SciQ | SciQ-5037 | energy-efficiency, thermal-insulation
greater if the window is bigger
less as temperature difference get smaller
Radiative heat transfer
The main factor that is of consideration here is the solar radiation. There are three types of radiation:
Direct radiation: the direct rays of the sun. (this is zero on a cloudy day).
Diffuse radiation: this is always present and its an effect of the presence of atmosphere. In higher latitudes it tends to increase because the sun rays need to "pass through" more atmosphere.
reflected (you can neglect this)
If you can get the rays of the sun (direct radiation) into the house, this will always be a significant plus in the heat balance of the house.
Final thoughts
This problem is very instance specific depending on:
the location of the house
orientation of windows
type of blinds, etc.
Therefore, it is impossible to draw a generic conclusion. As such, only trends can be realistically observed.
At a temperature difference of 30$[^oC]$ it makes sense to close the blinds on a cloudy day. However, if you get closer to 15$[^oC]$ then the savings are diminished.
If the windows are positioned in the right angle and light shines into the room, then expect the added solar radiation will improve the heat balance in favour of open blinds.
The following is multiple choice question (with options) to answer.
The sun’s heat can also be trapped in your home by using south facing windows and good what? | [
"vegetation",
"insulation",
"floors",
"curtains"
] | B | Solar energy is used to heat homes and water, and to make electricity. Scientists and engineers have many ways to get energy from the Sun ( Figure above ). One is by using solar cells. Solar cells are devices that turn sunlight directly into electricity. Lots of solar cells make up an individual solar panel. You may have seen solar panels on roof tops. The Sun’s heat can also be trapped in your home by using south facing windows and good insulation. |
SciQ | SciQ-5038 | cell-biology, hematology, red-blood-cell
Title: Why are red blood cells considered to be cells? Wikipedia states that a cell is
the basic structural, functional and biological unit of all known living organisms. Cells are the smallest unit of life that can replicate independently.
It then goes on to state that
All cells (except red blood cells which lack a cell nucleus and most organelles to accommodate maximum space for hemoglobin) possess DNA.
Then why are red blood cells still considered cells, while they can't replicate? Is the definition on Wikipedia just a bad definition? Or are red blood cells wrongly considered cells, but remain so for historical reasons? Or are they considered cells for some other reason, such as this answer which states that red blood cells do contain a nucleus at some point? A very good question, and it is most likely because of the last option. It had a nucleus for part of its life. After the RBC jettisons its nucleus, it still remains very metabolically active for approximately 3 months. It maintains its cell membrane integrity, it metabolizes glucose, it interacts constantly with its environment, numerous cellular functions and structure remain intact... It is extremely specialized for a primary purpose, and no longer requires the nucleus to provide more proteins. It has limited capacity to heal from injury, so it has a limited life span.
Speculation: I wonder if it might lose the nucleus early on so that when it is destroyed in the spleen at the end of its life as RBCs are, the spleen macrophages are not overwhelmed with additional processing of nucleic acids? Macrophage type cells are already working hard in there to clear infectious agents and some immune cells from the blood.
The following is multiple choice question (with options) to answer.
Red blood cells do not perform aerobic respiration, but they do perform what process that is nearly universal to organisms? | [
"mitosis",
"glycolysis",
"reproduction",
"digestion"
] | B | CRITICAL THINKING QUESTIONS 18. Why is it beneficial for cells to use ATP rather than energy directly from the bonds of carbohydrates? What are the greatest drawbacks to harnessing energy directly from the bonds of several different compounds? 19. Nearly all organisms on earth carry out some form of glycolysis. How does that fact support or not support the assertion that glycolysis is one of the oldest metabolic pathways? 20. Red blood cells do not perform aerobic respiration, but they do perform glycolysis. Why do all cells need an energy source, and what would happen if glycolysis were blocked in a red blood cell? 21. What is the primary difference between a circular pathway and a linear pathway?. |
SciQ | SciQ-5039 | universe, age
Title: Is it be correct to say that we live in a young (only 14 billion years old) universe? From what I have read, it seems that our universe is expected to function more or less as it does now for some $10^{12}$ years, possibly more. If that is correct, our universe's current age of $14$ billion years seems like this place we live in is still a baby, or at most a child.
I realize we are a long way from being sure about making such a broad characterization. Nevertheless, does it generally accord with current astronomical and cosmological thinking to say that our universe is still young? Calling something young or old is normally done in reference to some special age. For things that have limited lifespans it is usually the average life expectancy (old people are people who are close to or beyond the life expectancy). For things that can potentially remain arbitrarily long we compare to some typical timescale of their evolution, in particular the longest dynamical timescale (one might call a piece of a decaying radioactive element "old" when it has been around more than a few half-lives).
Since the current $\Lambda$CDM consensus model of the universe has an unlimited long future we need to find a good reference timescale.
We are living in the stelliferous era, when stars form and shine. This lasts from some hundred million years after the big bang until $10^{12}$ to $10^{14}$ years in the future. Many people implicitly assume a biocentric perspective thinking that life is only possible during this era and that the end of stars would be the end of the universe, at least the end of anything interesting. By this standard we are in the early part of the stelliferous, so it is a young universe.
The following is multiple choice question (with options) to answer.
Late adulthood begins in the mid-60s and continues until? | [
"birth",
"death",
"youth",
"adolescence"
] | B | Late adulthood begins in the mid-60s and continues until death. This is the stage of life when most people retire from work. This frees up their time for hobbies, grandchildren, or other interests. For example, the man in Figure below enjoys creating music in old age. |
SciQ | SciQ-5040 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
The concentration of a substance is the quantity of solute present in a given quantity of ___________? | [
"mixture",
"structure",
"solution",
"salutation"
] | C | Summary The concentration of a substance is the quantity of solute present in a given quantity of solution. Concentrations are usually expressed as molarity, the number of moles of solute in 1 L of solution. Solutions of known concentration can be prepared either by dissolving a known mass of solute in a solvent and diluting to a desired final volume or by diluting the appropriate volume of a more concentrated solution (a stock solution) to the desired final volume. |
SciQ | SciQ-5041 | geology, rocks, sedimentology, geomorphology, terminology
Title: What do you call boulders of non sedimentary rock that were lithified into sandstone? I'm convinced there is a word for this. I was in the Hoodoos at Writing on Stone this weekend and kept noticing what looked like reddish quartzite boulders laying around in the sand, or sometimes sticking partially out of the hoodoos.
When a non-sedimentary rock gets washed out into silt which later lithifies, what's it called? It's kind of like a conglomerate, except there's only a couple of really big rocks, which eventually fall out out the rock because all the sandstone around them eroded away. The technical term for a sedimentary rock that has a lithified fine-grained sediment with larger pieces of rocks suspended in it upon lithification is a conglomerate. The fine-grained interstitial part is called the matrix, and the large pieces suspended in it are called clasts. Clasts can range from gravel- to boulder-size. These are technical terms used by sedimentologists.
It is tempting to refer to these fragments as xenoliths but as that word has a very specific meaning in igneous petrology, it is best to avoid it to remove any confusion.
The following is multiple choice question (with options) to answer.
What is the study of rock strata called? | [
"biochemistry",
"chemistry",
"stratigraphy",
"biology"
] | C | The study of rock strata is called stratigraphy . The laws of stratigraphy can help scientists understand Earth’s past. The laws of stratigraphy are usually credited to a geologist from Denmark named Nicolas Steno. He lived in the 1600s. The laws are illustrated in the Figure below ; refer to the figure as you read about Steno's laws below. |
SciQ | SciQ-5042 | proteins, amino-acids, classification
Title: Classifying Polypeptides (and/or Proteins) Since polypeptides are a linear chain of twenty amino acids, each having a single letter abbreviation (e.g. Alanine = A). So can a polypeptide be represented as just the sequence (say: ADN for an Alanine, Aspartic acid, Asparagine polypeptide)?
This method of classifying polypeptides would lead to a possible 8000 (20**3) variations just for 3-amino-acid-polypetides (3200000 for 5-amino-acid-polypeptides, etc.) and that there would be many variations; and for longer polypeptides - that is, proteins - there would be even more variations.
Or are only the important polypeptides and proteins named, since not every variation of polypeptides and proteins are found in the body? I would've thought that many proteins (and enzymes, etc.) are incredibly specific and so they could be classified in some methodological way, as opposed to just 'lipase' or 'carbohydrase' which provides no structural information (though it would have a long methodological name). You can certainly refer to short peptides by their sequence. I don't know of any exact boundaries, but I've seen tripeptides referred to by either their three letter codes (Ala-Asp-Asn) or even the chemical name (alanylaspartylasparagine) although obviously that gets ridiculous pretty quickly.
As the largest known protein, titin also has the longest IUPAC name of
a protein. The full chemical name of the human canonical form of
titin, which starts methionyl... and ends ...isoleucine, contains
189,819 letters and is sometimes stated to be the longest word in the
English language, or any language. However, lexicographers regard generic names of chemical compounds as verbal formulae rather than English words
The following is multiple choice question (with options) to answer.
What is the particular sequence of amino acids in a longer chain called? | [
"atomic sequence",
"molecular sequence",
"amino acid sequence",
"carbon sequence"
] | C | The dipeptide has a free amino group on one end of the molecule and a free carboxyl group on the other end. Each is capable of extending the chain through the formation of another peptide bond. The particular sequence of amino acids in a longer chain is called an amino acid sequence. By convention, the amino acid sequence is listed in the order such that the free amino group is on the left end of the molecule and the free carboxyl group is on the right end of the molecule. For example, suppose that a sequence of the amino acids glycine, tryptophan, and alanine is formed with the free amino group as part of the glycine and the free carboxyl group as part of the alanine. The amino acid sequence can be easily written using the abbreviations as Gly-Trp-Ala. This is a different sequence from Ala-Trp-Gly because the free amino and carboxyl groups would be on different amino acids in that case. |
SciQ | SciQ-5043 | physiology, senescence, organs
Kidney: 7.2 years
Liver: 16.9 years
Lung: 2.1 years
Heart: 14.5 years
Kidney-Pancreas: 12.9 years
These numbers are not definite, since the life style of the donor and the receiver as well as infections of the transplated patient (who has a severely suppressed immune system – this is critical) also play an important role in determining the lifetime of the organ.
The following is multiple choice question (with options) to answer.
Stones, infections, and diabetes threaten the health and functioning of what paired organs? | [
"lungs",
"arteries",
"kidneys",
"tissues"
] | C | A person can live a normal, healthy life with just one kidney. However, at least one kidney must function properly to maintain life. Diseases that threaten the health and functioning of the kidneys include kidney stones, infections, and diabetes. |
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