source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-1044 | star, galaxy, history, definition, stellar-structure
Title: Metallicity of Celestial Objects: Why "Metal = Non-metal"? Metallicity of objects refers to the amount of chemical elements present in it other than Hydrogen and Helium.
Note: The other elements may or may not be actual metals in the true sense of their defintion.
The following is multiple choice question (with options) to answer.
Metalloids, metals, and nonmetals are all classes of what? | [
"protons",
"matter",
"elements",
"compounds"
] | C | Metalloids are the smallest class of elements. (The other two classes of elements are metals and nonmetals). There are just six metalloids. In addition to silicon, they include boron, germanium, arsenic, antimony, and tellurium. Metalloids fall between metals and nonmetals in the periodic table. They also fall between metals and nonmetals in terms of their properties. |
SciQ | SciQ-1045 | waves, pressure, acoustics, oscillators, vibrations
We can also address your question about why air doesn't fill in backwards. If we can assume an elastic medium, we know that the position and velocity of any particle movements are a function of cosine and sine respectively. With this, we can see that the reason the air only fills in from one side is that the air on the other side is in the process of moving away from that vacuum at that point in time. In fact, that air gets slowed down by this vacuum to a standstill, and that's what shapes the next cycle of the wave!
The following is multiple choice question (with options) to answer.
How does air always flow? | [
"left to right",
"in to out",
"high to low",
"low to high"
] | C | Cold air is dense, so it sinks. This creates a center of high pressure. Warm air is less dense so it rises. This creates a center of low pressure. Air always flows from higher to lower pressure. As the air flows, Earth’s surface rotates below it causing Coriolis effect. So while the wind blows into the low pressure, it revolves in a circular pattern. This wind pattern forms a cyclone. The same happens while the wind blows out of a high pressure. This forms an anticyclone. Both are shown in Figure below . |
SciQ | SciQ-1046 | optics, astronomy, reflection, metals, telescopes
I used a good lens, which is why the effect is so small, but this shows the principle behind it.
Exhibit D
This is a microwave door - it is opaque to microwaves, but as you can see, lets visible light through. (See Faraday Cage)
Exhibit E
WiFi. It can pass through walls and doors.
It should be clear now that light doesn't exactly behave like what our brain calls "light"
Finally
I hope this helps. As you can see - WAAAY to long for a comment.
The following is multiple choice question (with options) to answer.
What type of invisible waves are used in microwaves? | [
"radiation",
"thermal",
"electric",
"convection"
] | A | Did you ever wonder how a microwave works? It directs invisible waves of radiation toward the food placed inside of it. The radiation transfers energy to the food, causing it to get warmer. The radiation is in the form of microwaves, which are a type of electromagnetic waves. |
SciQ | SciQ-1047 | physiology, cardiology, blood-circulation
Title: What is the quality rate of intrinsic autoregulation in the heart? Autoregulation is the maintenance of constant blood flow to an organ in spite of fluctuations in Blood pressure.
It involves the relaxation of myocardium and contraction.
It is local.
I know that autoregulation is best done in the brain, well in kidneys and badly in skeletal muscle.
I am interested how it is in the heart.
I think it should be at least good.
Brain can be thought more important.
However, I am not sure.
How good is the autoregulation of the blood flow in the heart? My conjecture: Intrinsic regulation is done in the heart the second best, after the brain.
This idea is based on the fact that the brain controls heart's some autonomic functions.
It is an open research question how the autonomic nervous system affects the intrinsic functions of the heart - and the reverse is true too.
To answer this question, we need to understand the autonomic regulation of the heart better i.e. the inner-physiology of the heart's electrical activity.
The following is multiple choice question (with options) to answer.
Which muscular organ pumps blood all around your body? | [
"stomach",
"pancreas",
"lungs",
"heart"
] | D | When you think of muscles, you might think of biceps and the external muscles you see in a bodybuilder. However, some muscles are found deep inside your body. The heart, for example, is a very muscular organ. It has to pump blood all around your body. |
SciQ | SciQ-1048 | physiology
So, now the question is shifted: why do kisspeptin neurons show up only at puberty? We don't know for sure, but it looks like increased levels of E2 could be important for this.
Again, we get into a self-sustaining cycle. Growth of the body generates an increase in E2 production (possibly due to increased volume of the gonads?), which, when over a certain level permits the development of kisspeptin neurons, which will then stimulate the GnRH neurons, resulting in increased LH and E2. We then have more E2 and this makes kisspeptin neuron grow even more etc etc.
The following is multiple choice question (with options) to answer.
What causes the changes of puberty? | [
"insulin",
"testosterone",
"glucose",
"estrogen"
] | D | During adolescence, estrogen causes the changes of puberty. It causes the reproductive organs to mature. It also causes other female traits to develop. For example, it causes the breasts to grow and the hips to widen. |
SciQ | SciQ-1049 | 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.
If a sedimentary rock layer is not horizontal, what is it? | [
"deformed",
"mineralized",
"igneous",
"striated"
] | A | Sedimentary rock layers that are not horizontal are deformed. |
SciQ | SciQ-1050 | energy, visible-light, photons, sun, interactions
Title: What are the physical processes involved in feeling warm from the sunlight? Suppose a human is lying on a beach. He/she starts to feel warm after exposing his/her skin to the sunlight. I assume that feeling is due to the ability of the human body of "measuring" the increasing in temperature of the skin.
Now I want to understand what are the physical processes involved in this increasing in temperature.
Imagine a group of photons impinging on the skin in a certain interval of time. I tried to list the possible interactions from a particle physics perspective between photons and the human tissue and I concluded that the possible interactions may be:
Photoionization
Compton scattering
Rayleigh scattering
Pair production
The first 3 seems to be reasonable, but the fourth one requires an energy threshold too high: there are no incident photons that may have that energy. I conclude that by looking at the spectrum of sunlight that actually reaches the earth's surface below the atmosphere. So I think that the pair production does not play a role in this situation.
Are there any other interaction processes between photons and tissue molecules involved in the increasing of temperature of the human tissue?
After listing the processes I wonder what actually increases the temperature: is the temperature increasing because the photons-molecules interactions lead to a transition of molecules to excited vibrational states? or maybe transitions to excited rotational states?
I thought that another possibility is that the photons interactions are increasing the kinetic energy of the water molecules in the skin or maybe are increasing the lattice vibration of other tissue (skin, bones or others). Are this processes happening simultaneously? One of this processes (for example transition to rotational excited states) is dominant over the others ?
I'm looking to a qualitative answer, without going into too much details of the Biology of the human body. I just want to create an approximate picture of this situation in my mind. I want to create a mental "video" from the instant in which a photon or a group of photons impinges in the skin to the moment in which tissue molecules are affected and the temperature starts rising up.
I thank in advance anyone who answers this question. You forgot garden-variety absorption! Here, light promotes electrons from lower energy states to higher energy states. However, skin is made of many small particles, so scattering is important as well.
Here’s the mental video:
The following is multiple choice question (with options) to answer.
What system, which includes the skin, plays important roles in protection, sensing stimuli and thermoregulation? | [
"integumentary system",
"teleporters system",
"digestive system",
"pectins system"
] | A | 5.3 Functions of the Integumentary System The skin plays important roles in protection, sensing stimuli, thermoregulation, and vitamin D synthesis. It is the first layer of defense to prevent dehydration, infection, and injury to the rest of the body. Sweat glands in the skin allow the skin surface to cool when the body gets overheated. Thermoregulation is also accomplished by the dilation or constriction of heat-carrying blood vessels in the skin. Immune cells present among the skin layers patrol the areas to keep them free of foreign materials. Fat stores in the hypodermis aid in both thermoregulation and protection. Finally, the skin plays a role in the synthesis of vitamin D, which is necessary for our well-being but not easily available in natural foods. |
SciQ | SciQ-1051 | homework, plant-physiology, plant-anatomy
and 'Vascular Plants = Winning! - Crash Course Biology #37'
https://youtu.be/h9oDTMXM7M8?t=373
[5] Osmosis (water compensating solutes) "In Da Club - Membranes & Transport: Crash Course Biology #5"
https://youtu.be/dPKvHrD1eS4?list=PL3EED4C1D684D3ADF&t=148
Ian (and dad <= all errors and approximations are his :) ).
The following is multiple choice question (with options) to answer.
What type of plant tissue transports water and dissolved mineral upward to the leaves? | [
"xylem",
"phloem",
"ectoderm",
"collagen"
] | A | Xylem carries water and dissolved minerals from the roots upward to the leaves. |
SciQ | SciQ-1052 | optics, material-science
Title: What material can a lens be made from? I need to make a camera lens that can easily withstand temperatures of about 1000 Fahrenheit.
What should I make the lens out of? Fused silica should be ok at this temp. Sapphire will also be fine. It seems unlikely that the correct design is to have your lenses at this temperature though, can you share more about your problem?
The following is multiple choice question (with options) to answer.
What can lenses be used to make? | [
"comparison representations",
"function representations",
"aspect representations",
"visual representations"
] | D | Lenses can be used to make visual representations, called images . |
SciQ | SciQ-1053 | surface-tension
Title: What is the surface tension of liquids in space? I mean does surface tension exists in space on liquids?
Let's take an example if I have to write something using ballpen in space and space does not have gravity. Does it works because of the surface tension? Surface tension does exist "in space", which I take you to mean "without gravity". Surface tension in liquids is simply the attractive interactions between the molecules of a liquid. That exists whether there is gravity or not. I think most pens will not work well without being in the proper orientation in gravity, though. If you try using a normal ballpoint pen and write on a paper on the ceiling, you'll probably find that it won't work because gravity is pushing the ink in the wrong direction.
The following is multiple choice question (with options) to answer.
Surface tension is a property of matter that is in what state? | [
"liquid",
"water",
"mixture",
"Base"
] | A | Molecules within a liquid are pulled equally in all directions by intermolecular forces. However, molecules at the surface are pulled downwards and sideways by other liquid molecules, but not upwards away from the surface. The overall effect is that the surface molecules are pulled into the liquid, creating a surface that is tightened like a film. This phenomenon is referred to as surface tension . Liquids that have strong intermolecular forces, like the hydrogen bonding in water, exhibit the greatest surface tension. Table below shows surface tension values for various common liquids. |
SciQ | SciQ-1054 | physiology, respiration
Title: Why does a worm's skin need to be wet for oxygen to diffuse across it? Pages I've read about worms' respiratory systems says that the skin needs to be wet (covered in mucus) or oxygen won't diffuse across the skin. Why? If there is more oxygen outside the worm's skin than inside, what prevents it from diffusing across the skin, even if the skin is dried out? The quick answer: When the skin dries, the lipids in the cell membranes of the skin tissue undergo a phase transition which makes the membranes less permeable for oxygen.
Explanation: The lipids of the cell membrane can exist in different phase states. In the liquid disordered phase the lipids are relatively flexible and mobile, making this phase more oxygen permeable compared to the liquid ordered phase, in which the lipids are more rigidly packed.
The phase transition temperature of lipids increases upon dehydration (another reference), meaning that at the same ambient temperature, a dry lipid membrane is in the liquid ordered state and a wet lipid membrane is in the liquid disordered state.
Therefore, a dry cell membrane is less oxygen permeable than a wet one.
The following is multiple choice question (with options) to answer.
Amphibians have permeable skin which allows for the exchange of oxygen and carbon dioxide, what is this "breathing called?" | [
"benign respiration",
"variant respiration",
"aquatic respiration",
"cutaneous respiration"
] | D | Characteristics of Amphibians As tetrapods, most amphibians are characterized by four well-developed limbs. Some species of salamanders and all caecilians are functionally limbless; their limbs are vestigial. An important characteristic of extant amphibians is a moist, permeable skin that is achieved via mucus glands that keep the skin moist; thus, exchange of oxygen and carbon dioxide with the environment can take place through it ( cutaneous respiration). Additional characteristics of amphibians include pedicellate teeth—teeth in which the root and crown are calcified, separated by a zone of noncalcified tissue—and a papilla amphibiorum and papilla basilaris, structures of the inner ear that are sensitive to frequencies below and above 10,00 hertz, respectively. Amphibians also have an auricular operculum, which is an extra bone in the ear that transmits sounds to the inner ear. All extant adult amphibians are carnivorous, and some terrestrial amphibians have a sticky tongue that is used to capture prey. |
SciQ | SciQ-1055 | material-science
Title: Wood: A Naturally Occurring Composite Material? In materials science texts, I see wood used an example of a naturally occurring composite material. One of the main components of wood is cellulose, which is a polymer. But what other component makes it a composite?
Thanks for any clarification. the two components of wood-as-a-composite are cellulose fibers and lignin, the resin in which the cellulose fibers are embedded. Cellulose furnishes strength in tension and the resin furnishes strength in shear.
The following is multiple choice question (with options) to answer.
What is the main component of paper, cardboard, and textiles made from cotton, linen, and other plant fibers? | [
"vascular tissue",
"pulp",
"cellulose",
"cambium"
] | C | Cellulose is another polymer of glucose, consisting of anywhere from hundreds to over ten thousand monomers. It is the structural component of the cell walls of green plants and is the single most common organic molecule on Earth. Roughly 33% of all plant matter is cellulose. The linkage structure in cellulose is different than that of starch, and cellulose is indigestible except by a few microorganisms that live in the digestive tracts of cattle and termites. The figure below shows a triple strand of cellulose. There is no branching and the fibers adopt a very stiff rod-like structure with numerous hydrogen bonds between the fibers adding to its strength. Cellulose is the main component of paper, cardboard, and textiles made from cotton, linen, and other plant fibers. |
SciQ | SciQ-1056 | quantum-mechanics, thermodynamics, statistical-mechanics, terminology, gas
available as a pdf here, which makes the claim much more clear:
Quantum Gases
The configurational properties of low-molecular-weight gases (hydrogen, helium, neon) are described by quantum, rather than classical, statistical mechanics.
(The rest of that passage looks eerily similar to the one in your textbook. Is the Chueh & Prausnitz paper the reference 18 cited in your book? If it isn't, there's some pretty flagrant behaviour there.)
Basically, what they're claiming is that if you're studying the dynamics of a gas molecule leaving the liquid phase and into more open space, then classical mechanics is a good approximation so long as the molecule is massive enough, and that this approximation works well for all but the very lightest of molecules.
That's where your listing comes in: H$_2$, He and Ne are the lightest possible constituents of reasonable gases, as most everything in between will coalesce into diatomics that are heavier than neon. Presumably the claim goes that by the time you get to N$_2$ at mass 14 then the quantum mechanical effects become effectively negligible.
(And there are, of course, unreasonable gases ─ HF in particular, but also potentially Li$_2$ and Be$_2$ ─ which lie below that mass-$10$ cutoff, so presumably the fugacity calculations would need to be repeated for them, but I don't think that studying the equilibrium gas and liquid fractions of hydrofluoric acid as a function of temperature is a particularly appealing experiment.)
The following is multiple choice question (with options) to answer.
What theory explains the physical behavior of gases? | [
"thermodynamic theory of gases",
"kinetic theory of gases",
"quantum theory of gases",
"relativity theory of gases"
] | B | The physical behavior of gases is explained by the kinetic theory of gases. |
SciQ | SciQ-1057 | genetics, biochemistry, proteins, rna
Title: Where do amino acids get attached to tRNA and where is it synthesized? Some very basic parts of transcription/translation seem to be left out in various literature. I can't find the answer to this anywhere:
How exactly is tRNA synthesized? I realize that mRNA is synthesized through transcription and I know a lot about that. However tRNA is supposedly synthesized the same way but every time you read about transcription they just talk about how the mRNA then gets this and that...?
Where do the amino acids get attached? Is it in the nucleus or outside the nucleus?
Thanks. A pre-tRNA is transcribed from tRNA genes in DNA by RNA polymerase III. Processing occurs in the nucleus, where a 5' sequence is cleaved by RNase P, the 3's CCA motif is added, and ~10% of the nucleotides are substituted. The tRNA are transported out via the pore complexes. Aminoacyl-tRNA synthetase enzymes attach amino acids in the cytoplasm in a 2-step reaction that requires ATP. You'll find there's a unique splicing mechanism in tRNA that additionally splices out an anticodon intron which is abesnt in mature tRNA's:
The wikipedia article notes RNA Pol III generally recognizes internal control elements rather than upstream control elements as in a normal gene.
Source: Qiagen
Source: Molecular Cell Biology. 4th edition.
Addendum: I said in my post that tRNA is charged in the cytoplasm, this is somewhat true. In mammalian cells, we also see that tRNA are charged in the nucleus as well, and it might aid in the export of some of these charged tRNAs. (Source)
The following is multiple choice question (with options) to answer.
Only finished mrnas are exported from the nucleus to what? | [
"electron",
"amino acids",
"cerebellum",
"cytoplasm"
] | D | 9.3 Transcription In prokaryotes, mRNA synthesis is initiated at a promoter sequence on the DNA template. Elongation synthesizes new mRNA. Termination liberates the mRNA and occurs by mechanisms that stall the RNA polymerase and cause it to fall off the DNA template. Newly transcribed eukaryotic mRNAs are modified with a cap and a poly-A tail. These structures protect the mature mRNA from degradation and help export it from the nucleus. Eukaryotic mRNAs also undergo splicing, in which introns are removed and exons are reconnected with single-nucleotide accuracy. Only finished mRNAs are exported from the nucleus to the cytoplasm. |
SciQ | SciQ-1058 | human-anatomy, cardiology
Title: Structure separating the left atrium from the ascending aorta? With reference to the (adult) anatomy of the human heart:
The left atrium (LA) and the proximal part of the ascending aorta (Ao) abut one another, as shown nicely in this image [1]. Is there a name for the wall(s) separating the LA and Ao? And is this a single structure (i.e. septum), or is there a sinus?
[1] http://www.radiologyassistant.nl/data/bin/w440/a5097978b829cd_3-chamber.jpg There isn't any particular structure there: you have the wall of the aorta/adventitia, and if you have an explanted heart there is a space and then the auricle of the left atrium on one side and the right atrium on the other. These would all be contained within the pericardium.
Where the aorta is most "touching" the left atrium is where the pulmonary veins come in: I think this picture from Gray is most helpful.
Figure 494. Henry Gray (1825–1861). Anatomy of the Human Body. 1918.
There really isn't much to distinguish these veins from the non-auricle part of the atrium, similar to the vena cava on the right side. If you were to cut along the veins eventually you would just open up into the atrium.
The Visible Heart Lab is another good reference http://www.vhlab.umn.edu/atlas/aorta for cardiac anatomy.
The following is multiple choice question (with options) to answer.
What is the largest artery in the body called? | [
"carotid",
"subclavian",
"aorta",
"femoral"
] | C | Arteries are muscular blood vessels that carry blood away from the heart. They have thick walls that can withstand the pressure of blood being pumped by the heart. Arteries generally carry oxygen-rich blood. The largest artery is the aorta , which receives blood directly from the heart. |
SciQ | SciQ-1059 | physical-chemistry, color, light
Title: Colour due to transmission and reflection It makes sense to me that when looking through a sample (observer | sample | light), it should appear as the opposite of the light absorbed, but it does not make sense to me to expect the same when not looking through it, just standing by the same side as the light source (observer | light | sample, or light | observer | sample).
In the first cenario, the observer sees light emitted - light absorbed (the transmitted, that barely interacts with the sample). In the second, the observer sees light reflected (to my understanding, light emitted from the de-excitations of excitations caused by the light source).
However, when I see a solution of $Cu^{2+}$, it looks the same when observed in both settings. Thereby implying that transmitted colour = reflected colour. Why is that?
Somewhat related question but without a satisfactory answer: Transmission, absorption, and reflection of light Since your experimental observation with copper salts negates your original hypothesis, it implies that the way you are trying to explain it is wrong. The main culprit and the source of all these problems is the color wheel which is taught in schools. Misconceptions persist for long. When you are looking at the copper solutions in two different settings, it is misleading to think that copper solution is reflecting blue light back to you. It is not.
In each case, copper(II) solution is absorbing a small portion of the red light from the visible spectrum and it appears to you like a pure blue solution.
Indeed it is our brain which has been created in such a way that when the visible spectrum has a certain red portion missing, it perceives the remaining spectrum as "blue".
Hint: Water in the ocean also appears blue? Water also very very weakly absorbs the red portion of the visible spectrum. You just need tons of water to perceive this effect.
There is a beautiful book by the name of The Physics and Chemistry of Color. The same author wrote an article "The fifteen causes of color: The physics and chemistry of color." It is certainly worth consulting. Article-behind paywall
The following is multiple choice question (with options) to answer.
What type of change has occurred when a copper penny changes color? | [
"carbon change",
"chemical change",
"reactive change",
"contamination change"
] | B | Some of these pennies are shiny and copper colored. That’s how pennies look when they are new. The older pennies are dull and brown. Copper at the surface of these pennies has combined with air to become a different substance with different properties. The change in color shows that a chemical change has occurred. |
SciQ | SciQ-1060 | electric-circuits, electric-current, electrical-resistance, batteries, short-circuits
Title: The importance and the role of a switch in an electrical circuit There is this simple test:
Three identical bulbs are connected in the circuit illustrated in the figure. When switch $S$ is closed:
a] The brightness of $A$ and $B$ remains the same, while $C$ goes out.
b] The brightness of $A$ and $B$ remains the same, while that of $C$ is halved.
c] The brightness of $A$ and $B$ decreases while $C$ goes off.
d] The brightness of $A$ and $B$ increases while $C$ goes off.
For my opinion the answer to this question is D because the switch (which has a resistance of $0\, \Omega$ has a node connected before the third bulb C) that "interrupts" the circuit. But, going into detail, according to Kirchhoff's first law the current should also go on the third bulb as in the first red node it divides into two currents $I_1$ and $I_2$. The current $I_1$ goes for example in the key $S$ and $I_2$ in the third bulb. The key and the third bulb have the same potential difference. I believe that the current $I_2$ passes through the third bulb but the current passing through it is so small that it does not turn on.
I made a point. When an individual is operated on at the heart and puts a by-pass (a bridge), blood will flow on the tube that detects the by-pass and the occluded artery (the third bulb) where blood will flow slowly, over time it will atrophy.
If the circuit were like the one drawn in the picture I would answer the b).
My question is: I have not very clear the rule of a switch in a eletric-circuit.
In fact, I find it difficult to give an answer to the following image.
The following is multiple choice question (with options) to answer.
A switch in a circuit controls the flow of what, specifically, within the circuit? | [
"resistance",
"current",
"pressure",
"density"
] | B | Many circuits have switches to control the flow of current through the circuit. When the switch is turned on, the circuit is closed and current can flow through it. When the switch is turned off, the circuit is open and current cannot flow through it. |
SciQ | SciQ-1061 | genetics, cell-biology, embryology, meiosis, gamete
Title: Fertilization of the human egg- where does our centrosome come from? Is there a centrosome in a human egg cell? Is the reason why the egg cell remains paused before meiosis 2 because there isn't a centrosome, and it only divides when the sperm fertilizes it thus it can have a centrosome? If this is so, then how did oogenesis happen? ? To answer the first part of your question. The sperm actually introduces two centrosomes. The centrosome then nucleates the new microtubule assembly to form the sperm aster — a step essential for successful fertilization. You can visit these sites Simerly, et al as well as Paweltz, et al
The following is multiple choice question (with options) to answer.
What causes fertilization to occur? | [
"genetic and an egg fuse",
"accumulation and an egg fuse",
"tissue and an egg fuse",
"sperm and an egg fuse"
] | D | Many animals have a relatively simple life cycle. A general animal life cycle is shown in Figure below . Most animals spend the majority of their life as diploid organisms. Just about all animals reproduce sexually. Diploid adults undergo meiosis to produce sperm or eggs. Fertilization occurs when a sperm and an egg fuse. The zygote that forms develops into an embryo. The embryo eventually develops into an adult. |
SciQ | SciQ-1062 | evolution, botany, development, fruit, seeds
What is the point of fruit if not to be eaten? It’s my understanding that organisms will adapt to survive and thrive. I understand that being eaten can spread seeds, but this just seems like too much of a risky tactic to rely on.
Following on from part one: If being eaten is the best way to spread seed, why do some plants avoid this (such as by being poisonous or thorny)? Seeds are spread by many mechanisms
Wind dispersal: When air currents used to spread seeds. Often these plants have evolved features to facilitate wind catching, for example dandelions. Aka, anemochory.
Propulsion & bursting: When seeds are propelled from the plant in an such as in these videos. This is called Ballochory.
Water: Similarly to wind dispersal plants can spread seeds by water movement/currents, aka Hydrochory. This is used by many algae and water living plants.
Sticky Seeds: There are many ways a seed can attach to the outside of an animal - by using hooks, barbs, sticky excretions, hairs. Seeds then get carried by an animal and fall off later. This is epizoochory.
Fruiting: Plants can use seed-bearing fruit to encourage animals to eat the seeds. They will then be spread when the waste is excreted after digestion. This is a process of endozoochory.
More than one way to spread a seed
The following is multiple choice question (with options) to answer.
Because they spread seeds, fruits are an agent of what? | [
"disposal",
"propagation",
"dispersal",
"predation"
] | C | Fruit The seed forms in an ovary, which enlarges as the seeds grow. As the seed develops, the walls of the ovary also thicken and form the fruit. In botany, a fruit is a fertilized and fully grown, ripened ovary. Many foods commonly called vegetables are actually fruit. Eggplants, zucchini, string beans, and bell peppers are all technically fruit because they contain seeds and are derived from the thick ovary tissue. Acorns and winged maple keys, whose scientific name is a samara, are also fruit. Mature fruit can be described as fleshy or dry. Fleshy fruit include the familiar berries, peaches, apples, grapes, and tomatoes. Rice, wheat, and nuts are examples of dry fruit. Another distinction is that not all fruits are derived from the ovary. Some fruits are derived from separate ovaries in a single flower, such as the raspberry. Other fruits, such as the pineapple, form from clusters of flowers. Additionally, some fruits, like watermelon and orange, have rinds. Regardless of how they are formed, fruits are an agent of dispersal. The variety of shapes and characteristics reflect the mode of dispersal. The light, dry fruits of trees and dandelions are carried by the wind. Floating coconuts are transported by water. Some fruits are colored, perfumed, sweet, and nutritious to attract herbivores, which eat the fruit and disperse the tough undigested seeds in their feces. Other fruits have burs and hooks that cling to fur and hitch rides on animals. |
SciQ | SciQ-1063 | genetics, molecular-biology, cell-biology, cancer, mutations
Title: Question about proto-oncogenes and oncogenes? My textbook says:
Growth-promoting genes are called proto-oncogenes. Some can be changed into oncogenes by a point mutation that alters the ability of the proto-oncogene to be switched off. They remain permanently switched on. Oncogenes promote unregulated cell division. Such cell division leads to a tumour.
Does this mean that the change from proto-oncogene to oncogene is not a mutation in the exon, but rather in the intron?
I hope I used these terms correctly. Thank you for any help :) I am going to add to @MattDMo 's answer a bit.
Proto-oncogenes Function, Developmental Program, and Regulation
Proto-oncogenes are normally functioning genes that are more often than not in the pathways that lead to mitosis and cellular replication. They have important roles in the development, growth, and maintenance of the organism. Proto-oncogene is an accurate description of the genes, but I unfortunately think that sometimes people think that the genes themselves are bad and that isn't the case.
Growth and development in multicellular organisms are highly regulated processes with many checks and balances. Certain cells need to grow in certain places at certain times, and then they need to go into and remain in interphase. If they don't, or they do things at the incorrect times, the multicellular organism will not develop properly or will develop conditions such as cancer.
It is often these points of regulation that become dysregulated when a proto-oncogene becomes oncogenic. If there are regions of allostery that are affected by a mutation in the coding sequence (exon) and a control molecule that represses the activity of the enzyme through conformation change can no longer bind, then that enzyme can remain active, always turned on.
You can also have a situation where you have transcriptional regulators of proto-oncogenes that can be effected making the gene product oncogenic. If there is a mutation in an enhancer (intronic) of the gene that affects the binding kinetics of enhancers leading to a great increase in transcription, this concentrational difference can lead to uncontrolled grown and tumor formation.
The following is multiple choice question (with options) to answer.
Proto-oncogenes normally help regulate what? | [
"cell death",
"cell function",
"cell transition",
"cell division"
] | D | |
SciQ | SciQ-1064 | cell-biology
Title: Structure of Cell Are cells spheres or ovals/circles bound by phospholipidbilayer?
If they are spherical how are we able to see the nucleus through the phospholipid bilayer under a microscope? Not exactly. That is a stereotype of cells. Muscle cells are not round nor oval, but rather elongated rods. If you were to look up epithelia cells, you can quickly see that cells are grouped based on their physical characteristics; simple (round/oval & single layer), columnar, and cuboidal to name a few. Cells come in many shapes and sizes. As Hans stated, stains are vital in viewing cellular components. There is a diverse amount of stains used - which all carry a purpose and benefit in a specific application.
The following is multiple choice question (with options) to answer.
The "double helix" shape is associated with what substance found in cells? | [
"plasma",
"genes",
"bacteria",
"dna"
] | D | data are passed to new generations; and even how proteins are built to required specifications. All these abilities depend on the pairing of complementary bases. Figure 19.7 "Complementary Base Pairing" shows the two sets of base pairs and illustrates two things. First, a pyrimidine is paired with a purine in each case, so that the long dimensions of both pairs are identical (1.08 nm). If two pyrimidines were paired or two purines were paired, the two pyrimidines would take up less space than a purine and a pyrimidine, and the two purines would take up more space, as illustrated in Figure 19.8 "Difference in Widths of Possible Base Pairs". If these pairings were ever to occur, the structure of DNA would be like a staircase made with stairs of different widths. For the two strands of the double helix to fit neatly, a pyrimidine must always be paired with a purine. The second thing you should notice in Figure 19.7 "Complementary Base Pairing" is that the correct pairing enables formation of three instances of hydrogen bonding between guanine and cytosine and two between adenine and thymine. The additive contribution of this hydrogen bonding imparts great stability to the DNA double helix. |
SciQ | SciQ-1065 | biophysics, theoretical-biology, ecosystem
Systems ecology, especially with regard to energy and nutrient flow.
This type of ecology can be strongly influenced by physics. For one example see the book Theoretical Ecosystem Ecology: Understanding Element Cycles by Ågren & Bosatta (Ågren was originally a physicist)
Physical limitations to growth and transport
This can include for instance mechanical contraints on plant growth (see e.g. the book Plant Physics by Nicklas & Spatz), water transport in trees (see e.g. this BioSE question) or the biomechanics of movement (see e.g. Hudson et al (2012) on the speed and movement of cheetahs or Wikipedia: Biomechanics).
Allometric relationships between organisms, e.g. with regard to metabolism
To explain these types of relationships knowledge in physics is useful. See e.g. Kleiber's law for more.
MAXENT as a general approach to ecological patterns or to model species distributions
This is basically a tool lifted from physics that can be applied to ecological problems. There are many papers to look at, but Harte & Newman (2014) (Harte is another previous physicist) and Elith et al (2010) are two good starting points.
Dynamical modelling of populations and communities
This field use many of the same tools for analysis as physics, e.g. systems of differential equations. One of the pioneers in this field (among many) were Robert May (also started with a PhD in physics), and his classical book Theoretical Ecology: Principles and Applications is still a good starting point.
Energy harnessing and conversion by organisms
This can refer both to how organsims convert prey to energy (e.g. conversion efficiencies) and the physics of photosynthesis (which is an interesting intersection between physics and molecular biology). See Jang et al (2004) and O'Reilly & Olaya-Castro (2013) for examples of the how quantum mechanics can inform us about photosynthesis.
Hopefully this will give you a sense of some different ways that knowledge in physics can be useful for biology.
The following is multiple choice question (with options) to answer.
What do you call the physical environment in which a species lives and to which it is adapted? | [
"environment",
"habitat",
"domain",
"ecosystem"
] | B | An ecosystem consists of all the biotic and abiotic factors in an area and their interactions. A niche refers to the role of a species in its ecosystem. A habitat is the physical environment in which a species lives and to which it is adapted. Two different species cannot occupy the same niche in the same place for very long. |
SciQ | SciQ-1066 | planets
Title: What is Venus's core made of? As we all know Venus's surface is so hot that it can probably melt lead.
What would be in it's in core?
Is it in the liquid or solid state?
What would be it's temperature?
How many cores does it have? Scientists think that Venus' internal structure is somewhat like Earth's, as shown below:
In other words, a crust, mantle, and core. The evidence points to Venus not having plate tectonics like Earth or a magnetic field. Venus also probably has a partially molten core, like Earth, as it has been cooling at the same rate.
Honestly, we don't know much else. We can tell you the atmosphere composition, but we don't know what the core is made up of. The Venus Wikipedia page (here) is very helpful and has more information and explanations of why we don't know these things.
The following is multiple choice question (with options) to answer.
What is the outer core made of? | [
"compressed air",
"solid iron",
"solid rock",
"liquid metal"
] | D | Yes! The outer core, anyway. The outer core is liquid metal, like in this photo. Of course, the metal is under an incredible amount of pressure. |
SciQ | SciQ-1067 | cell-biology, microbiology
Title: Are there any organisms that are made of more than one (~5-12) cell? Prokaryotes and eukaryotes are unicellular, made of one cell. Great. Eukaryotes are unicellular or multicellular. But the typical examples of multicellular eukaryotes we have are made of, often, trillions of cells, like us humans. Ants must still be made of many millions of cells. Are there known eukaryotes with very few cells that make them up? Like, 5, or something? Or maybe a dozen cells making up the whole organism in its fully developed state? There's Trichoplax adhaerens, a Placozoa, made of a few thousand cells. Then there is Dicyema japonicum, a simple mesozoan, made up of 9 to 41 cells. Arguably, the simplest multicellular organism is the algae Tetrabaena socialis, whose body consists of 4 cells. Then, there's the parasitic Myxozoa which have 7 cells.
The following is multiple choice question (with options) to answer.
What type of eukaryotes are protists normally? | [
"immature",
"photosynthetic",
"multicellular",
"unicellular"
] | D | Most protists are so small that they can be seen only with a microscope. Protists are mostly unicellular (one-celled) eukaryotes. A few protists are multicellular (many-celled) and surprisingly large. For example, kelp is a multicellular protist that can grow to be over 100-meters long ( Figure below ). Multicellular protists, however, do not show cellular specialization or differentiation into tissues. That means their cells all look the same and, for the most part, function the same. On the other hand, your cells often are much different from each other and have special jobs. |
SciQ | SciQ-1068 | body diagram of the situation. You can use the Inclined Plane – Simple Machine Gizmo™ to see how inclined planes can help to lift objects. An inclined plane of angle θ = 20. The inclined plane is one of the six classical simple machines defined by Renaissance scientists. A cylinder of mass m = 250 g and length l = 10 cm is placed on an inclined plane of a rake angle α = 30 °. Materials: spring scale, object: block of wood or similar object, flat board, string, masking tape, protractor. QUESTIONS: 1. A very important application in mechanics is the inclined plane. First draw a free body diagram of the block. Floating displays using a DCRA have the space efficiency problem of having a system thickness equal to the height of the floating image and the problem of a ghost image interrupting the visibility of the floating display. It allows one to use less force to move an object. A ramp is the most basic example of an inclined plane. The lecture begins with the application of Newton’s three laws, with the warning that they are not valid for objects that move at speeds comparable to the speed of light or objects that are incredibly small and of the atomic scale. 0-kilogram object accelerating at 10. In today's lab, you will be investigating how different angles of an inclined plane affect the easiness to pull up an object. Acceleration = m/s 2 compared to 9. A force of magnitude $$T=\text{312} \text{N}$$ up an incline is required to keep a body at rest on a frictionless inclined plane which makes an angle of $$\text{35}$$ $$\text{°}$$ with the horizontal. Compute The Component Of The Gravitational Force Acting Down The Inclined Plane. A body resting on a plane inclined at at an angle α to the horizontal plane is in a state of equilibrium when the gravitational force tending to slide the body down the inclined plane is balanced by an equal and opposite frictional force acting up the inclined plane. angle of inclination: The angle that the inclined surface makes with the horizontal ground. Get an answer for 'Work on an incline plane. Simple machines are tools that make your work easier. ) and Inclined Planes Overview. Most things would rapidly slide across a floor that was slanted almost vertically steep. Then, measure the distance from that point to the bottom of the plane. Lifting a load vertically straight up takes
The following is multiple choice question (with options) to answer.
An inclined plane is a good example of what kind of machine? | [
"complex",
"weak",
"simple",
"strong"
] | C | An inclined plane is also a simple machine. The resistance is the weight of the box resting on the inclined plane. In order to lift this box straight up, the effort force would need to be equal to its weight. However, assuming no friction, less effort (a smaller effort force) is required to slide the box up the incline. We know this intuitively; when movng boxes into a truck or onto a platform, we use angled platforms instead of lifting it straight up. |
SciQ | SciQ-1069 | thermodynamics, ideal-gas
Title: What is the pressure at a random point inside container of an ideal gas? In most textbooks and thermodynamic lectures, the pressure is defined as the force on the walls of containers due to the incassecant beating of gas molecules divided by the area of the wall. Now, suppose I take a random point inside the container, what would be it's pressure at equilibrium and also non equilibrium conditions?
I am confused on the point whether we should have a wall or not to define pressure like is pressure a quantity defined 'over' the boundary of the container and undefined inside and outside? This seemed strange, to resolve, I thought of taking some random surfaces inside the container (say maybe a imaginary sphere) and then computing the pressure.
If the gas is in equilibrium,
$$ P \overline{V} = RT$$
and, if we calculate temperature from the temp of gas (all points have same because equilibrium) then we find pressure same for all points inside a gas. However this still is weird because how can you talk of 'pressure' without having a physical membrane which is being hit upon. Many physical quantities are defined in terms of "what would happen if ..." For example we might define the electric field strength at a point as the force per unit charge that acts on a small 'test' charge placed at the point, but we consider the electric field still to exist at the point, even if we don't have a test charge there.
It's similar with pressure. We consider a small surface to be placed at the point in question, even if that point is somewhere in the middle of the gas. We define the pressure as the force per unit area acting normally to that surface. We can measure the pressure with a sensor, and we can compute the pressure theoretically from the molecular impacts on an imaginary surface. But we still talk about the pressure at that point even if we don't have the surface there. It's the way we use the word.
The following is multiple choice question (with options) to answer.
The pressure of a sample of gas is measured with an open-end what? | [
"barometer",
"altimeter",
"manometer",
"thermometer"
] | C | The pressure of a sample of gas is measured with an open-end manometer, partially shown to the right. The liquid in the manometer is mercury. Assuming atmospheric pressure is 29.92 in. Hg, determine the pressure of the gas in: (a) torr (b) Pa (c) bar. |
SciQ | SciQ-1070 | ocean, ocean-currents, tides
Direct disruption of seabed habitats by physical interference, e.g. from moorings
Disruption of ecological niches: Some organisms have evolved to survive in areas where others cannot - e.g. high current speed environments. Changes in seabed conditions, e.g. from greater or lesser current speeds, may cause them to be out-competed by other species that can then settle there.
Similarly, changes to sediment distribution represent changes to seabed habitats.
Alteration of flow patterns could have implications for species with a dispersive juvenile stage (e.g. larvae that rely on currents to spread) or those that rely on current flow for nutrient or waste transport.
The following is multiple choice question (with options) to answer.
Bog destruction in scotland is an example of the widespread loss of what kind of habitat? | [
"desert",
"ocean",
"tundra",
"wetland"
] | D | A habitat that is quickly being destroyed is the wetland . By the 1980s, over 80% of all wetlands in parts of the U. S. were destroyed. In Europe, many wetland species have gone extinct. For example, many bogs in Scotland have been lost because of human development. |
SciQ | SciQ-1071 | botany, terminology, fruit
Title: What is the name of this part in plants, fruits, vegetables? What is the name of this part of the plant, fruit, vegetable? The thing that the plant is connected with the tree and gets nutrients with? The part we usually cut out when eat fruit.
Examples below
Papaya
Banana
Mango 'Stalk' or 'pedicel' would be an appropriate term (see, for example, this paper or this one). Specifically, you could say 'terminal part of the stalk/pedicel', though I don't know if there is a word for that.
Note that the term pedicel is commonly used for the stalk of a flower; it makes sense to use it for fruits too as they are derived from flowers.
The following is multiple choice question (with options) to answer.
What part of the plant has a root end and a shoot end? | [
"leaves",
"pistol",
"radius",
"axis"
] | D | |
SciQ | SciQ-1072 | material-science, physical-chemistry
Title: Melting and Boiling Points of Odd Materials In Chemistry, I was taught that there are three main states of matter: solid, liquid, and gas, and that heat and pressure determine that state. For some substances, the line is blurry between them.
Some materials don't seem intuitively to do this--nor have I been able to find data on them. For example, what is a reasonable estimate of a melting point for brick? What is the boiling point of paper? When will a carpet sublimate?
The common theme seems to be that these are all composite materials. Certainly all the elements have melting points (as applicable) and boiling points. Many compounds do too. However, something like cardboard is a mixture of fiber, glue, pigment, and possibly other things. Each of these might be made up of several compounds, with each compound having its own boiling point.
My suspicion is that for composite materials, individual compounds would exhibit properties roughly individually--so to melt wood, the water would boil off first, and then maybe it would start melting into a glucose-protein slag. Is this truly the right idea for what happens? This is an interesting question, because there is no simple answer - many different things are going on. A quick answer is that many materials don't exhibit clear melting points because heating turns them into something else before they can melt. Here are a couple of examples:
Generally, pure substances have simple, well-defined melting and boiling points. But there are many exceptions. A key example is gypsum - CaSO4 . 2H2O - calcium sulfate dihydrate. When it's heated, it first dehydrates in two steps. Initially it loses 1.5 of the water molecules as vapor, then in a second phase it loses the last 1/2 water molecule as vapor. When this dehydration is complete, the remaining compound is not the compound that we started with - it is now CaSO4. And if heating is continued, much of the CaSO4 will decompose - producing CaO (solid) and SO3 (vapor). Eventually, some melting will be observed, but the melted material will actually be a mixture of CaO and CaSO4.
The following is multiple choice question (with options) to answer.
Hardness, density, color, and melting and boiling points are all considered what types of properties? | [
"chemical",
"physical",
"thermal",
"visible"
] | B | Physical properties include color, density, hardness, and melting and boiling points. |
SciQ | SciQ-1073 | endocrinology
Title: Abnormal Prolactin Level I want to know what makes the balance of the Prolactin abnormal. Is that related to the presence of a nodule near the pituitary? The main abnormality in prolactin levels is hyperprolactinemia, meaning blood levels of prolactin above the normal range, not during pregnancy or lactation.
The major cause of these abnormal prolactin levels are tumors consisting of pituitary lactotroph cells--called prolactinomas--which secrete prolactin. This is generally corrected with synthetic dopamine analogues, as dopamine negatively regulates secretion of prolactin in lactotroph cells.
Here is a 2010 review with further detail:
http://joe.endocrinology-journals.org/content/206/1/1.full.pdf
The following is multiple choice question (with options) to answer.
Low levels of thyroid hormones in the blood cause the release of what by the hypothalamus and pituitary gland? | [
"enzymes",
"bases",
"acids",
"hormones"
] | D | You can see an example of a negative feedback loop in Figure below . It shows how levels of thyroid hormones regulate the thyroid gland. This loop involves the hypothalamus and pituitary gland as well as the thyroid gland. Low levels of thyroid hormones in the blood cause the release of hormones by the hypothalamus and pituitary gland. These hormones stimulate the thyroid gland to secrete more hormones. The opposite happens with high levels of thyroid hormones in the blood. The hypothalamus and pituitary gland stop releasing hormones that stimulate the thyroid. |
SciQ | SciQ-1074 | nuclear-physics, mass-energy
Title: Why does mass change in to energy during a nuclear change? I have been doing some research on nuclear changes and I have found that the energy released during a nuclear change comes from a minuscule amount of mass that is converted in to energy. After making some more research it seemed completely logical because of Einstein’s famous energy equation, but I was left with a couple of questions roaming my mind.
The following is multiple choice question (with options) to answer.
The energy changes in what reactions are enormous compared with those of even the most energetic chemical reactions, and they result in a measurable change of mass? | [
"nuclear reactions",
"metabolic reaction",
"molecular reaction",
"methane combustion"
] | A | To understand the differences between nuclear fission and fusion. Nuclear reactions, like chemical reactions, are accompanied by changes in energy. The energy changes in nuclear reactions, however, are enormous compared with those of even the most energetic chemical reactions. In fact, the energy changes in a typical nuclear reaction are so large that they result in a measurable change of mass. In this section, we describe the relationship between mass and energy in nuclear reactions and show how the seemingly small changes in mass that accompany nuclear reactions result in the release of enormous amounts of energy. |
SciQ | SciQ-1075 | states-of-matter, matter
Title: What distinguishes the difference states of matter from solid to BEC and perhaps fermionic condensate? Is it something to do with the behavior of electrons? How many states are there either discovered or predicted? 無
'States of matter' is a question of taxonomy, not of reality, and moreover, it's a result of the conditions surrounding the matter, not its internal properties. Certain combinations of properties give us a hint towards calling something 'solid' or 'liquid', but in truth there are no lines, just a continuous spectrum, and under certain conditions, matter transitions seamlessly through all sorts of states, both mundane and exotic:
Behold: Jupiter
A perfect example of this is Jupiter. Composed primarily of hydrogen, this gas giant consists (conjecturally) of a core of high-temperature hydrogen ice, floating in liquid hydrogen, enveloped in hydrogen gas, moving through interplanetary medium composed of hydrogen plasma.
Except not really: Under these conditions, the classical notions of states of matter break down entirely: Between these states of matter there are no interfaces, just a gradual, continuous transition.
In other words: The distinctive line to separate one state from another you are after doesn't really exist.
The following is multiple choice question (with options) to answer.
What type of chemistry is the study of the composition of matter? | [
"analytical",
"philosophical",
"symbolic",
"reactive"
] | A | Analytical chemistry is the study of the composition of matter. It focuses on separating, identifying, and quantifying chemicals in samples of matter. An analytical chemist may use complex instruments to analyze an unknown material in order to determine its various components. |
SciQ | SciQ-1076 | evolution, virology
Title: How did viruses come to be? My question is out of curiosity and got me thinking. How did viruses with the head, tail and tail fibres actually evolve? These viruses look more like machines than biological entities. Are there any theories to how these viruses evolved? I found a book chapter for you here
Quick summary:
3 hypotheses to Origin of viruses
From pre-cellular world (virus first hypothesis)
From reductive evolution of parasites (reduction hypothesis)
From fragments of cellular genetic material (escape hypothesis)
Drawbacks:
virus require cells (to infect) so how can they come first
virus do not look like known reduced parasites from Bacteria/Eukarya/Archaea
unlikely that genetic fragments form complex viral structures for viral function
Because of these drawbacks, the problem of virus origin was for a
long time considered untractable and not worth serious consideration
The rest of the chapter looks more in-depth into the 3 hypotheses
The following is multiple choice question (with options) to answer.
Scientists did not actually see viruses until what was invented? | [
"telescope",
"electron microscope",
"magnifying glass",
"electronic scale"
] | B | Scientists did not actually see viruses for the first time until the 1930s. That’s when the electron microscope was invented. The virus shown in Figure below was the first one to be seen. |
SciQ | SciQ-1077 | mitochondria, energy-metabolism
decrease viscosity of myofilaments so they slide more easily over each other.
increase enzyme activity since more enzyme-substrate complexes form as enzymes and substrates move faster with greater chances to collide which increases the rate of ATP formation and utilisation.
relax blood vessel smooth muscles resulting in vasodilatation and increased blood flow, with consequent increases in oxygen supply and lactic acid removal during excercise. Whether lactic acid causes fatigue depends on the difference between the rate of its production and the rate of its flushing during activity. At rest, the remaining lactic acid is flushed or oxidised locally. We maintain the vasodilatation and high ventillation rate at rest, to oxidise the remaining lactic acid and myoglobin and form ATP by the ETC to rephosphorylate creatine to phosphocreatine (oxygen debt). The flushed lactic acid is mostly reoxidised into pyruvic acid then glucose in the liver by reversal of glycolysis, also known as gluconeogenesis (Cori cycle). The remaining lactic acid is reoxidized locally to pyruvic acid which enters Krebs' cycle instead, but the majority is flushed. The increased blood supply also helps in healing from microtrauma at rest which ultimately stops soreness. Cold, on the other hand, treats soreness directly by decreasing blood flow carrying inflammatory cells that cause pain by secreting cytokines.
Besides increasing temperature, uncoupling causes
faster flow of electrons through the ETC since the sufficient proton back-pressure is never established so ATP synthase doesn't inhibit pumping of protons and electron transfer (electron transfer is continuous). As a result, oxygen is reduced rapidly to water instead of being reduced merely to hydrogen peroxide that can cause damage if catalase is saturated and can't split the excess to water and oxygen.
The following is multiple choice question (with options) to answer.
Regularly done aerobic activities can help build up endurance and make what vital organ stronger? | [
"heart",
"brain",
"stomach",
"skin"
] | A | Tim Wilson. Regularly done aerobic activities can help build up endurance and make the heart stronger . CC BY 2.0. |
SciQ | SciQ-1078 | book-recommendation
Title: Suitable writings for self-study in general biology/chemistry I have recently commenced a graduate education in mathematics. Since I am currently attending extra classes in programming, which are not included in my education, my institution will not let me attend further courses in biology. Hereby, my question is simple:
What are suitable writings for self-study in general biology/chemistry? By general, I mean somewhat of an university-level introduction of mentioned fields.
My level of knowledge is slightly above "advanced" high school chemistry/biology.
(I apologize for my bad english, I'm Norwegian.) My personal favorite intro biology book is Campbell Biology. The new edition is a little pricy, but you can probably find one of the older editions for pretty cheap--my intro class used 9th edition, and I don't think much has changed other than some of the taxon names.
I'm not sure what branch of Bio you're interested in, but Campbell covers all of introductory cell biology, organismal/evolutionary and ecology. The "concept check" questions at the end of each chapter are fantastic open-ended responses, and I believe most (if not all) have answers in the back of the book
I'm not as solid in general chemistry, but some good ones I remember are Brown, Lemay, and Burston which got me through AP Chem, and Zumdhal which my university uses and I haven't heard any complaints. The Brown text is a pretty good intro though. It provides good information and I thought it was pretty enjoyable to read.
The following is multiple choice question (with options) to answer.
What do all chemical sections need to get started? | [
"energy",
"work",
"speed",
"pressure"
] | A | The bonds between the atoms need to be rearranged. That is the definition of a chemical reaction. And all chemical sections need energy to get started. |
SciQ | SciQ-1079 | botany
Title: Do plants absorb toxins from the soil? Consider a plant like Aloe Vera that grows up in a toxic environment where the concentration of pesticides, and materials like lead, mercury, cadmium, arsenic etc is very high(e.g. Marshland dumping yard ). Would that mean that the extract from these plants would contain all these toxic elements. Not "all of them". But yes, plants suck up water from the soil, with everything dissolved in this water - nutrients, heavy metals, poisons. And also they breathe air, and absorb stuff via this route.
There probably are some toxins which will not enter the plant, because their molecules are too large and/or fragile. For example, should a plant root come in contact with snake venom, I cannot imagine that any venom will end up stored in the plant leaves.
Plants also have their own metabolism, so they will change/deactivate some toxins. I've seen claims that some plants "purify" formaldehyde, although I don't trust the sources enough to be sure of that.
But the smaller the poison molecule, and the less similar to stuff which is usually digested in nature, the more likely that it will enter the plant and stick around instead of being broken down. The heavy metals you mentioned are prime candidates. If they are present in the groundwater - or also lead from air pollution, before we banned leaded gasoline - they end up in plants, including food plants. And mushrooms are even more at risk.
Growing food near waste dumps is a known problem in farming, and sometimes makes the news, for example here:
http://bigstory.ap.org/article/mafia-toxic-waste-dumping-poisons-italy-farmlands
The following is multiple choice question (with options) to answer.
What do people apply to their lawns that causes water pollution? | [
"seeds",
"manure",
"water",
"chemicals"
] | D | People pollute water when they apply excess chemicals to their lawn. They may also dispose of pollutants incorrectly. |
SciQ | SciQ-1080 | 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 do vertebrates possess that is made up of repeating bony units? | [
"spinal cord",
"notochord",
"skull",
"vertebral column"
] | D | repeating bony units that make up the vertebral column of vertebrates. |
SciQ | SciQ-1081 | time
With respect to the Sun, the Earth rotates once every 24 hours. But because the Sun's apparent position changes in the sky due to Earth's revolution around the Sun, the Earth rotates once every 23 hours, 56 minutes, 4 seconds with respect to the stars. Because of this 3 minutes, 56 seconds difference, all stars rise and set 3 minutes, 56 seconds earlier each succeeding day. This applies to the time of a star passing through the meridian as well.
So, on the next day, April 29, Arcturus will pass the meridian at 22:56:04.
And what day does the Arcturus will pass the meridian about 01:00:00?
Over the course of an entire year, about 365 days and 6 hours, these 3 minutes and 56 seconds adds up to an entire day, so that exactly one year later, the same star will pass through the meridian at the same time of day.
For Arcturus to pass the meridian exactly 22 hours earlier, it should be 22/24 of a year before then, or about 335 days later, or about 30 days earlier, or March 29.
solar time equal sidereal time minus 12hr
Generally not correct. Solar time is based on the average time it takes for the sun to cross the meridian (24 hours), and sidereal time is based on the time it takes for a star to cross the meridian. Sidereal time counts 24 "hours" in 23 hours, 56 minutes, and 4 seconds, meaning that it runs slightly faster than our normal solar time.
There is one day in which solar and sidereal time are 12 hours off, on the northward equinox in March. The Sun is on the northward equinox, but solar time is measured since midnight where sidereal time is measured since passing the meridian (local noon).
There is one day in which solar and sidereal time coincide, on the southward equinox in September. The Sun is on the southward equinox, 180 degrees in the sky from the northward equinox, so the 12 hours off from midnight and the Sun being 12 hours off from the northward equinox cancel.
The following is multiple choice question (with options) to answer.
How long does it take for earth to rotate on it's axis one time? | [
"6 hours",
"12 hours",
"24 hours",
"26 hours"
] | C | Earth rotates on its axis every 24 hours. |
SciQ | SciQ-1082 | thermodynamics, energy, energy-conservation, phase-transition, physical-chemistry
Title: Why is Energy change occurring during the reaction at constant temperature and constant volume given by internal energy change? When volume and temperature are kept constant, shouldn't internal energy remain constant (as it's a state function depending on state variables)? When heat is supplied, why does the internal energy increase if state variables are kept constant? For a system likely to be the seat of a chemical reaction, the variables of state are not limited to the temperature and the volume: it is necessary to add the extent of reaction.
The following is multiple choice question (with options) to answer.
In what system can energy change forms but the total amount of energy stay constant? | [
"primary",
"heterogeneous",
"open",
"closed"
] | D | In a closed system, energy may change forms but the total amount of energy is constant. |
SciQ | SciQ-1083 | genetics, immunology, ecology, biodiversity, fitness
Title: What does genetic diversity in one species have to do with survival rate when an epidemic spreads? I was studying about genes, and soon remembered that the more diverse the genetics of one species, the less the chance of the species to go extinct from natural disaster.
One instance was an epidemic spreads.I don't fully understand why that happens, so I searched for it in Google and books, but all of them only told me that it is true, not why or how.
So my question is : why and how genetic diversity in one species affects the chance of the species's extinction?
I mean, for example, does it relate to antibodies or something else? Genetic diversity could be understood as a variation in alleles (gene variants) and their frequencies in a population. Due to these allelic variations, we would expect an inherent variability in individual genotypes (or genetic codes). Phenotypes (or traits) can and do vary with changes in underlying genotype. (In simple terms: if you change the underlying genetic code, it could result in changes to an individual's traits).
Changes in traits (e.g., color, size, speed, temperature regulation, mobility, etc.) could lead to a variation in energy conservation, survival, reproductive success, and ultimately fitness.
If any member of a population is more fit given a set of environmental circumstances, it is morel likely that they will survive and pass on their genes to subsequent generations.
You would benefit from reviewing evolution and natural selection. (Sexual selection and genetic drift are relevant, too, of course).
However, the environment and resulting ecologies are always changing, and so there is never an "endpoint" of this process. I.e., there's never a perfectly fit individual that will survive all future environmental changes better than all other variants. In fact, all organisms can only tolerate stressful environmental conditions to a point. (See, e.g., principle of allocation).
As a result, any given individual is limited in its ability to survive various environmental conditions, and no individual organism can survive all possible environmental conditions.
The following is multiple choice question (with options) to answer.
What characteristics of an organism help it survive? | [
"additions",
"adaptations",
"Changes",
"systems"
] | B | Some of the characteristics an organism has may help it survive. These characteristics are called adaptations . Some adaptations are better than others. |
SciQ | SciQ-1084 | physical-chemistry, equilibrium, solubility
But in this case there are three different ions and products possible by hydrolysis, so I am unable to find out which of them should be considered as the dominant species.
EDIT - M.L.'s answer clarified the calculations involved. My main confusion now is regarding why $\ce{HPO4^2-}$ (and not $\ce{H2PO4^-}$ or $\ce{H3PO4}$), will be the major ionic species in the solution. Is there a way to predict this based on values of $\mathrm{pK_a}$ and the $\mathrm{pH}$ of the solution? Okay, so I managed to get a solution without too many equations by making the right approximations.
First with your expressions:
$\ce{K_{sp} = [Mg^2+][NH_4^+][PO_4^3-]}$
$\ce{K_{sp} = (S)(0.1)(S-x})$
Here we want to find S-x which is $\ce{[PO_4^3-]_{eq}}$. To do this, I did the following:
$\ce{\frac{[PO_4^3-][H+]}{[HPO_4^2-]}=K_{a3} = 10^{-12.4}}$
Assuming $\ce{[H^+] = 10^{-10}}$:
$\ce{\frac{[PO_4^3-] 10^{-10}}{[HPO_4^2-] 10^{-12.4}}=K_{a3} = 1}$
$\ce{\frac{[PO_4^3-] 10^{2.4}}{[HPO_4^2-]} = 1}$
Now we could continue on and find $\ce{[H_2PO_4]}$. But it turns out the value is quite small and can be essentially ignored. Here is what we'll get if we solve for it:
The following is multiple choice question (with options) to answer.
The major component of a solution is called what? | [
"solute",
"water",
"mixture",
"solvent"
] | D | The major component of a solution is called the solvent. The minor component of a solution is called the solute. By major and minor we mean whichever component has the greater presence by mass or by moles. Sometimes this becomes confusing, especially with substances with very different molar masses. However, here we will confine the discussion to solutions for which the major component and the minor component are obvious. Solutions exist for every possible phase of the solute and the solvent. Salt water, for example, is a solution of solid NaCl in liquid water; soda water is a solution of gaseous CO2 in liquid water, while air is a solution of a gaseous solute (O2) in a gaseous solvent (N2). In all cases, however, the overall phase of the solution is the same phase as the solvent. |
SciQ | SciQ-1085 | atmosphere, ocean, hydrology, climate-change
Comment: I strongly endorse the use of wind and hydropower as sources of energy over the further use of fossil fuels. However, I still think it is important to do research into the actual renewability of presumed-renewable energy sources, as we don't want to end up with another fossil fuel-type situation, in which we become aware of dependency on these energy sources and their malignant environmental side-effects long after widespread enthusiastic adoption. Electricity from waves, from hydro (both run-of-river and storage) and from wind, are all indirect forms of solar power. Electricity from tides is different, and we can deal with that in a separate question. Global tidal electricity generation is not yet at the scale of gigawatts, so it's tiny for now.
Winds come about from the sun heating different parts of the planet at different rates, due to insolation angles, varying cloud cover, varying surface reflectivity, and varying specific heat of surface materials. Temperature differentials create wind currents.
Waves come about from wind, so they're a twice-indirect form of solar power.
Sunlight on water speeds up evaporation, lifting the water vapour into clouds, giving them lots of gravitational potential. That rain then falls, sometimes onto high land, from where it can be gathered into storage reservoirs that are tapped for electricity, or where it flows into rivers that are then harnessed in run-of-river hydro.
How much power is there? Well, the insolation from the sun is, at the outer boundary of the Earth's atmosphere, at an intensity of about 1400 Watts per square metre. The Earth's albedo is roughly about 30% - i.e. on average about 400 Watts are reflected back into space, giving an average irradiation into the Earth of about 1000 Watts per square metre. Picture the Earth's surface as seen from the Sun: wherever the Earth is in its orbit on its own axis, and around the Sun, the Sun sees a disc that has the Earth's diameter, so the surface area exposed to the Sun is just $\pi$ times the square of Earth's radius, which is about 6 300 kilometres.
So the incoming solar radiation is $1000 \times 6,300,000^2 \times \pi \approx 125 \times 10^{15} \rm \ W$
The following is multiple choice question (with options) to answer.
What type of pollution is generated by power plants and factories that can directly raise the temperature of water? | [
"Space Pollution",
"thermal pollution",
"variable pollution",
"atmospheric pollution"
] | B | Thermal pollution raises the temperature of water. It is commonly caused by power plants and factories. The change in temperature can kill fish and other water organisms. |
SciQ | SciQ-1086 | evolution, abiogenesis
So the argument - roughly - is that 10^-77 * 10^40 is still very small. That is, mutations are not frequent enough to overcome the extreme rarity of functional sequences.
The sleight of hand, I think, is to confuse abiogenesis and mutation. When talking about the entire 'landscape' of possible sequences we are talking about abiogenesis - randomly picking 150 amino acids (say) from an alphabet of 20. When talking about bacteria we are obviously talking about mutation.
We really have no idea how the first primordial proteins formed, or what their properties were. They could have used a smaller set of amino acids (although this does not change the numbers much), or could have assembled from multiple smaller peptides, or even been partially folded.
On the other hand, mutation of existing proteins necessarily happens on sequences that can already fold. Moving to a sequence that is a neighbour in fold space is very different to picking a completely new point in that space.
So really, the numbers do not tell us anything because they relate to separate questions.
The following is multiple choice question (with options) to answer.
Nearly all of what are constructed from a set of just 20 common amino acids? | [
"complex proteins",
"artifical proteins",
"biological proteins",
"mammal proteins"
] | C | Nearly all biological proteins are constructed from a set of just 20 common amino acids. The names, abbreviations, and other information for each of these amino acids are presented in the Table below . |
SciQ | SciQ-1087 | thermodynamics, water, phase-transition, evaporation, gas
Title: Why does water turn into water vapor? I read an article lately and it said that water turns into steam when it reaches its boiling point. But it led me to another question.
Why does water boil and why does the water turn into gas when it boils? Water molecules have attractive forces between them and form the liquid state.
First of all start with a container with water liquid and a vacuum above the water liquid.
This container and the water within it is kept at a constant temperature.
Some the water liquid molecules will have enough kinetic energy to overcome the attraction of their neighbouring water liquid molecules and escape from water liquid surface and become water vapour.
There is a net migration with water liquid molecules becoming water vapour molecules.
As time goes on and the number of water vapour molecules increases but some of those water vapour molecules will hit the water surface and become part of water liquid.
Eventually there are sufficient water vapour molecules and a dynamic equilibrium will be set up where the rate at which water liquid is converted into water vapour is exactly the same as the rate at which water vapour is converted into water liquid.
The pressure of the water vapour when this condition is satisfied is called the saturated vapour pressure.
Increasing the temperature means that the average kinetic energy of the water molecules increases and so the probability of a water liquid escaping from the surface of the liquid is increased.
So the rate at which water liquid turns to into water vapour increases.
For a time there is a net migration from water liquid to water vapour until the increase in the density of water vapour is sufficient for a new dynamic equilibrium to be set up.
The saturated vapour pressure increases as the temperature increases.
Raising the temperature will thus increase the saturated vapour pressure until there comes a temperature when the density of the vapour is the same as the density of the liquid.
The boundary (surface) between the liquid and the vapour disappears and you have just one phase.
That temperature is called the critical temperature and here is one video showing this effect.
Water liquid does not exist above the its critical temperature of $374\,^\circ \rm c$
The following is multiple choice question (with options) to answer.
What takes place when water on earth’s surface changes to water vapor? | [
"evaporation",
"absorption",
"condensation",
"transpiration"
] | A | Evaporation takes place when water on Earth’s surface changes to water vapor. The sun heats the water and gives water molecules enough energy to escape into the atmosphere. Most evaporation occurs from the surface of the ocean. |
SciQ | SciQ-1088 | zoology, ecology
Giraffes' this is an energy saving feature. Giraffes don't need to use muscles to hold their neck. They just use when flexing their necks down, when drinking water etc.
According to Wikipedia, for an alternative hypothesis Ouranosaurus have a hump. (Other hypothesis is display sail or termoregulation sail of course. Also spinosaurus have this kind of alternative hypotesis but this hypothesis not accepted much as sail. and spinosaurus' spine different from bisons. Bison spines concentrating at shoulder but spinosaurs' not at the shoulder. You can find spinosaurus info from this page.)
The following is multiple choice question (with options) to answer.
The muscles of the anterior neck assist in deglutition also known as what? | [
"breathing",
"pulling",
"swallowing",
"staring"
] | C | carbon atoms and the properties that result from that bonding. Hydrocarbons with only carbon-to-carbon single bonds (C–C) and existing as a continuous chain of carbon atoms also bonded to hydrogen atoms are called alkanes (or saturated hydrocarbons). Saturated, in this case, means that each carbon atom is bonded to four other atoms (hydrogen or carbon)—the most possible; there are no double or triple bonds in the molecules. |
SciQ | SciQ-1089 | virology, infection
Title: Why don't viruses cause wounds? A simple mental model of a viral infection is that an infected cell emits a lot of virions and eventually dies. The emitted virions have a chance of infecting other cells. Nearby cells are at a higher risk of infection.
Based on this model, if one cell in my nose gets infected, I would expect a large part of my nose to be destroyed, as the infection spreads and destroys more and more cells in the same area.
This does not happen! I survived a number of infections and still have my nose. Why?
I know there are "flesh eating" bacteria. Why isn't this the norm for infections? Does a common cold virus or SARS-CoV-2 not infect a lot of cells within the same area? A virus does not destroy that many cells before it is exterminated by the immune system or before the host dies.
Perhaps even more crucially, viruses typically target a very specific type of cell — those on the inner mucal surface of the nose in the case of cold or flu, those of the gastrointestinal tract in the case of stomach viruses, CD4 immune cells in the case of HIV, etc.
Update
As an example of how much time it takes for a virus to eat a noticeable wound, one could take the extermination of the immune cells by HIV - although it does not look as a physical wound, it is one, in the sense that enough of the specific tissue is destroyed to cause a life-threatening condition. It takes about a decade(!) - from the initial infection to the immune system failure.
On the other hand, the lethal effect of typical respiratory viruses is typically via obstructions of the respiratory ways due to inflammation or secretions resulting from the immune response, or via creating suitable conditions for a more serious bacterial infection.
The following is multiple choice question (with options) to answer.
Cells infected with viruses secrete what example of early induced proteins, which travel to adjacent cells and induce them to make antiviral proteins, a sacrifice that protects the surrounding cells? | [
"prokaryotes",
"metabolites",
"hormones",
"interferons"
] | D | Early induced Proteins Early induced proteins are those that are not constitutively present in the body, but are made as they are needed early during the innate immune response. Interferons are an example of early induced proteins. Cells infected with viruses secrete interferons that travel to adjacent cells and induce them to make antiviral proteins. Thus, even though the initial cell is sacrificed, the surrounding cells are protected. Other early induced proteins specific for bacterial cell wall components are mannose-binding protein and C-reactive protein, made in the liver, which bind specifically to polysaccharide components of the bacterial cell wall. Phagocytes such as macrophages have receptors for these proteins, and they are thus able to recognize them as they are bound to the bacteria. This brings the phagocyte and bacterium into close proximity and enhances the phagocytosis of the bacterium by the process known as opsonization. Opsonization is the tagging of a pathogen for phagocytosis by the binding of an antibody or an antimicrobial protein. |
SciQ | SciQ-1090 | evolution
Title: How to define "evolution"? The standard answer found in intro course to evolutionary biology to the question:
what is evolution?
is:
It is a change in allele frequency over time!
I believe a complete definition should encompass the following concepts:
mutations
copy number variation (CNV)
codon usage
chromosome numbers
phenotypic change (whether heritable or not)
Complex phenotypic trait such as plasticity and developmental noise
maybe some other things...
My questions are:
Would it be worth it to talk about phenotype in a definition of evolution?
What are the alternative definitions that have been proposed?
What is your definition?
Note: I would rather talk about genetic evolution, but if you think it is worth making one definition for genetic and cultural (and some other stuff maybe) evolution, you're free to suggest it! What is evolution?
In a non-biological sense, evolution means change:
"a process of [...] change"
Biological evolution (seeing as this is Biology stack exchange) then needs to be tweaked to give a biologically specific context. Many textbooks etc. give definitions of evolution and here are a few good ones from across the history of evolutionary biology:
Charles Darwin:
"Descent with modification".
Mark Ridley1:
"Evolution means change, change in the form and behaviour of organisms between generations. ... When members of a population breed and produce the next generation we can imagine a lineage of populations, made up of a series of populations through time. Each population is ancestral to the descendant population in the next generation: a lineage is an ancestor-descendent series of populations. Evolution is then change between generations within a population lineage."
Brian and Deborah Charlesworth2:
"Evolution means cumulative change over time in the characteristics of a population of living organisms. ... All evolutionary changes require initially rare genetic variants to spread among the members of a population, rising to high frequency..."
All of these have a common theme. Biological information is moving through time, descending with a degree of directionality (e.g. parent $\rightarrow$ offspring), and the information is modified with time.
Personally I would define evolution as:
The following is multiple choice question (with options) to answer.
What term is used to describe changes to an organism’s dna and are an important driver of diversity in populations? | [
"adaptations",
"evolutions",
"mutations",
"pathogens"
] | C | Mutation Mutations are changes to an organism’s DNA and are an important driver of diversity in populations. Species evolve because of the accumulation of mutations that occur over time. The appearance of new mutations is the most common way to introduce novel genotypic and phenotypic variance. Some mutations are unfavorable or harmful and are quickly eliminated from the population by natural selection. Others are beneficial and will spread through the population. Whether or not a mutation is beneficial or harmful is determined by whether it helps an organism survive to sexual maturity and reproduce. Some mutations do not do anything and can linger, unaffected by natural selection, in the genome. Some can have a dramatic effect on a gene and the resulting phenotype. |
SciQ | SciQ-1091 | organic-chemistry, nomenclature, carbonyl-compounds
P-65.1.2.1 Carboxylic acid groups, $\ce{{}-COOH}$, that conceptually replace a $\ce{{}-CH3}$ group of methane or terminate an unbranched hydrocarbon chain are named by replacing the final ‘e’ of the name of the corresponding hydrocarbon by the suffix ‘oic acid’. No locants are necessary to denote the positions of the carboxylic acid groups in a hydrocarbon chain; locants are used when hydrocarbon chains are modified by skeletal replacement, as shown in P-15.4.3.2.3. Except for formic acid, acetic acid, oxalic acid (see P-65.1.1.1), and oxamic acid (see P-65.1.1.1), systematically formed names are preferred IUPAC names; the names given in P-65 .1.1.2 are retained names for use in general nomenclature.
That’s why the name of the unsubstituted parent structure of the first compound that is given in the question is a heptanedioic acid.
P-65.1.2.2.1 If an unbranched chain is linked to more than two carboxy groups, all carboxy groups are named from the parent hydride by substitutive use of the suffix ‘carboxylic acid’, preceded by the appropriate numerical prefix ‘tri’, ‘tetra’ etc. and appropriate locants.
That’s why the name of the second compound is pentane-1,3,5-tricarboxylic acid.
The following is multiple choice question (with options) to answer.
Molecules with a carboxyl group are called what? | [
"Fatty acids",
"acetic acids",
"carboxylic acids",
"catalyzed acids"
] | C | Molecules with a carboxyl group are called carboxylic acids. As with aldehydes, the functional group in carboxylic acids is at the end of a carbon chain. Also as with aldehydes, the C atom in the functional group is counted as one of the C atoms that defines the parent hydrocarbon name. To name carboxylic acids, the parent name of the hydrocarbon is used, but the suffix -oic acid is added:. |
SciQ | SciQ-1092 | angular-momentum, astrophysics, orbital-motion, galaxies
Title: Why are some galaxies flat? What is the explanation for the flatness of some galaxies?
(If it's due to their rotation then why they are rotating, why some other galaxies are not flat etc., I would like to hear a nice and complete answer :) ) One interesting fact is that there are some revolving structures in space that aren't mostly flat - they're known as elliptical galaxies. And the difference here is that elliptical galaxies usually don't have much gas or dust in them. Interestingly enough, the orbits of objects in the inner solar system also tend to be coplanar, whereas the orbits of the minor planets in the outer solar system tend to be more inclined (or non-coplanar)- the difference here, again, is that there was less gas and dust in outer solar system (back during the era of accretion, and still true today)
So, back to the original question. When there's lots of dust in a galaxy, the galaxy tends to collapse into the planar shape of a spiral galaxy (to maintain angular momentum and to minimize gravitational potential energy). Which is the same thing that happens in the inner solar system.
And why does that happen? Well, we first go into the answer here: http://www.quora.com/Astronomy/Why-are-some-galaxies-disk-shaped-and-not-spherical. As Leo C. Stein explains...
The following is multiple choice question (with options) to answer.
What type of galaxies have a rotating disk of stars and dust, a bulge in the middle, and several arms? | [
"spherical galaxies",
"round galaxies",
"pinwheel galaxies",
"spiral galaxies"
] | D | Spiral galaxies have a rotating disk of stars and dust, a bulge in the middle, and several arms spiraling out from the center. The disk and arms contain many young, blue stars. |
SciQ | SciQ-1093 | photosynthesis, respiration, ecosystem, decomposition
Maybe you should study the metabolic processes of plants and life in general to better understand this. All life consists of chemical reactions that build up structures; in order to build them up you need energy (because of the second law of thermodynamics), and all living things create that energy by breaking down complex molecules into simpler ones. (as such it would be more accurate to say that all life consists of chemical reactions that build up and break down various structures). You might be wondering "but what about the difference between autotrophs and heterotrophs I heard about"; the difference between those is where they get the complex molecules from in the first place. Autotrophs use a different source of energy to build them up while heterotrophs get them from their environment. As such, you can think of every living thing as being made of two kind of molecules: those that actually form their structure (in humans, the molecules that make up cell membranes, bones, muscles, etc) and those that are stored in order to be broken down to power the whole system (in humans that's fat, glycogen, glucose, etc). Of course a molecule can do both; if you're starving your body may start to break down structural molecules for power. There are many different ways of breaking down those big molecules for power; the most efficient one, that starts with a big chain of carbon atoms and cuts it down into individual CO2 molecules using O2 molecules, is called aerobic respiration (i.e. respiration that uses oxygen).
Because those complex molecules are required to power all life, autotrophs (the organisms that actually make them) are very important, and the processes they use to make them are very important too. The process that makes almost all of the molecules that power almost all life on earth is photosynthesis, which uses the energy from the sun to power a reaction that converts CO2 from the atmosphere into big carbon-based molecules we'll call carbohydrates. This is called "fixing carbon", since the carbon atom is the most important one; measuring how much photosynthesis is happening is another way of measuring how many carbon atoms move from being part of a CO2 molecule to being part of a plant.
The following is multiple choice question (with options) to answer.
How is carbon dioxide and water vapor that is produced by cellular respiration released? | [
"peroxidation",
"evaporation",
"exhalation",
"fermentation"
] | C | A: Breathing consists of inhaling and exhaling, and its purpose is to move gases into and out of the body. Oxygen needed for cellular respiration is brought into the body with each inhalation. Carbon dioxide and water vapor produced by cellular respiration are released from the body with each exhalation. |
SciQ | SciQ-1094 | evolution, reproduction, terminology, population-genetics, fitness
Title: What's the difference between evolution fitness and reproductive success? What's the difference biological fitness and reproductive success in the biological terminology? The concepts are very similar but there are a few differences.
Firstly, fitness is usually applied to alleles or genotypes, reproductive success to individuals.
Secondly (and partially as a consequence of this), fitness is an average or idealised/expected property across a population; but actual reproductive success per individual is stochastic. Individuals possessing an allele with a relative fitness of "2" will on average have twice as many offpsring as their competitors, all else being equal, but individual reproductive success will vary as a consequence of other factors such as predation, parasitism, starvation etc.
Finally, absolute fitness relates to the proportional representation of a genotype in a population. Reproductive success relates to offspring per individual. For example, in a growing population a genotype could be simultaneously declining in proportion while it is increasing in absolute number, if other genotypes are increasing in number more rapidly.
The following is multiple choice question (with options) to answer.
What occurs when there are differences in fitness among a population? | [
"natural process",
"evolution",
"natural selection",
"natural change"
] | C | Natural selection occurs when there are differences in fitness among members of a population. As a result, some individuals pass more genes to the next generation. This causes allele frequencies to change. |
SciQ | SciQ-1095 | botany, terminology, nomenclature
Regnum Animale: the animals;
Regnum Vegetabile: the plants;
Regnum Lapideum: the minerals (you read it right).
Note that, in this classification, "animals" correspond to what nowadays we call animals and protozoans, and "plants" correspond to what nowadays we call plants, algae, fungi and bacteria.
You have to keep in mind that this book was first published in 1735, well before the evolutionary biology being proposed in the XIX century and established in the XX century. Therefore, it is a book published when fixism was the current paradigm, full of mentions to the scala naturae.
So, the plants (as well as the animals) showed a continuum of species, going to the lower plants (the bacteria) to the higher plants (the flowering ones). It's worth mentioning again that, by that time, bacteria were plants: Phylum Schyzophyta, to be more precise.
Thus, we have "lower plants" and "higher plants", "lower animals" and "higher animals", as well as "lower minerals" and "higher minerals"!
Unfortunately, this terminology is so embedded in the biological sciences that even today, as I mentioned, we struggle to get rid of it.
Just drop "higher plants", whatever it means
As your Wikipedia link says, "higher plants" is a synonym of vascular plants. However, there are a lot of problems here:
First, this is a remnant of the scala naturae and, just because of that, should be avoided. Think of it as a meaningless term, just like "more evolved organism".
Second, there is no clear and indisputable definition of what is a "higher" plant. Some authors used to define the "higher plants" as the Angiosperms only, or the seed plants (Angiosperms + Gymnosperms), or the vascular plants (Angiosperms, Gymnosperms and Pteridophyta).
For instance, in lusophone biology books, it was very common a division in three groups:
lower plants: bacteria and algae;
intermediate plants: bryophytes and pteridophytes;
higher plants: gymnosperms and angiosperms.
The following is multiple choice question (with options) to answer.
A group of living things and their environment is called what? | [
"ecosystem",
"population",
"community",
"biome"
] | A | An ecosystem is a group of living things and their environment. The word ecosystem is short for “ecological system. ” Like any system, an ecosystem is a group of parts that work together. You can see examples of ecosystems in Figure below . The forest pictured is a big ecosystem. Besides trees, what living things do you think are part of the forest ecosystem? The dead tree stump in the same forest is a small ecosystem. It includes plants, mosses, and fungi. It also includes insects and worms. |
SciQ | SciQ-1096 | optics, visible-light, wavelength, vision, biology
Color blindness is due to this biological mechanism being misaligned .
. Why is the UV invisible only sometimes?
. Does it have to do with the flower using iridescent structures to produce color, instead of a pigment?
Now ultraviolet frequency reflecting from materials as in the photos you show, may interact with them and give the perception of "seeing" ultraviolet, and that will depend on the material, which explains the differences in seeing an ultraviolet effect or not in the visible.
Can this happen with red and green, as well?
It might, i.e. the frequency scattering off a material may be degraded in energy and change the frequency( color) a bit. One would have to shine a fixed frequency red or green to see if there is an effect on the particular material.
The following is multiple choice question (with options) to answer.
Iridescent green beetles, known as jewel beetles, change color because of the light-reflecting properties of the cells that make up this? | [
"their hairs",
"their scales",
"their external skeleton",
"their wings"
] | C | Each section contains a liquid crystal sample with a different liquid crystalline range. The section whose liquid crystalline range corresponds to the temperature of the body becomes translucent (here shown in green), indicating the temperature. We also see the effect of liquid crystals in nature. Iridescent green beetles, known as jewel beetles, change color because of the light-reflecting properties of the cells that make up their external skeletons, not because of light absorption from their pigment. The cells form helices with a structure like those found in cholesteric liquid crystals. When the pitch of the helix is close to the wavelength of visible light, the cells reflect light with wavelengths that lead to brilliant metallic colors. Because a color change occurs depending on a person’s angle of view, researchers in New Zealand are studying the beetles to develop a thin material that can be used as a currency security measure. The automobile industry is also interested in exploring such materials for use in paints that would change color at different viewing angles. With only molecular structure as a guide, one cannot precisely predict which of the various liquid crystalline phases a given compound will actually form. One can, however, identify molecules containing the kinds of structural features that tend to result in liquid crystalline behavior, as demonstrated in Example 11. |
SciQ | SciQ-1097 | evolution, terminology, natural-selection, computational-model, definitions
On the other hand suppose we have some environment in which there are two anisofit fitness related hereditary material populations. Now if some environmental, or recombinative genetic change inflicts those two populations, that works either in a neutral manner, i.e. causes equal population sizes of those anisofit fitness related hereditary material, or works in an opposite-directional manner, i.e. in a direction that is opposite of the expected direction mentioned above, better be termed as "contra-directional". In this situation even if the size of the populations of those hereditary materials is different (imparting the appearance of a selection) still that difference is not explained by the effect of those anisofit fitness related hereditary material on their fitness in that environment! So this would not be an example of natural selection! It would be an example of an environmental factor that caused a "genetic drift", or of a genetic recombination process that caused a "genetic drift" also.
So we in effect have a struggle between "natural selection" which works in the direction of increasing adaptation with the environment, on one hand, and "random selection" (or sometimes called neutral selection or non-selection) which doesn't necessarily work in the direction of increasing adaptation with the environment.
So in some sense "evolution" is determined by the struggle of those two kinds of mechanism of change.
If random change prevails, then evolution would not necessarily move in the direction of increasing adaptation of living organisms with their environment. While if "natural selection" prevails, then evolution would proceed in the direction of increasing adaptation to the environment. I've mostly skimmed the formalism you introduced, but getting to the 2nd half of your post, the answer is yes, you understood correctly the distinction between natural selection (aka adaptive evolution) and drift (aka neutral evolution), as well as the fact that it's not a given that natural selection would be the predominant effect in arbitrary circumstances. Small population sizes, high rates of mutation, weak genetic repair mechanisms, etc. can all lead to chance being the predominant effect.
The conditions needed for natural selection to be predominant have been investigated in lots and lots of publications. A quick overview and brief list of such publications is found in
Duret, L. (2008) Neutral theory: The null hypothesis of molecular evolution. Nature Education
The following is multiple choice question (with options) to answer.
The effects of which kind of selection are larger than the effects of direct natural selection on individuals? | [
"topical selection",
"stranger selection",
"kin selection",
"unnatural selection"
] | C | |
SciQ | SciQ-1098 | superconductivity
Title: What exactly is superconductivity? Does superconductivity mean that the coulomb force or some magnetic force has gone up? I guess that it applies only to wires which get less resistance due to cooling... Is this wrong?
Also, Are there different kinds of superconductive states?
Is there a kind of superconductivity only for magnetism? Before thinking about Superconductivity, let's see Resistivity. Current flow appears in a direction when free electrons travel in opposite direction. During the traverse of free electrons, there would be a lot of collisions with atoms in the metal lattice. Hence, "Atoms experience vibrations about their mean position due to the passing waves of free electrons depending upon the temperature." (Thermal activity plays some role here)
By Ohm's law, resistance $R=\frac{V}{I}$ and also $R=\rho\frac{l}{A}$ where $\rho$ is the Specific resistance or Resistivity. Note that, these are only for normal conductors...
But for superconductors, this is not applicable for sure. Because, something happens differently in superconductors. At extremely low temperatures, the vibrations of atoms slow down so much that they synchronize with those passing waves of electrons..! (i.e.) The free electrons pass unobstructed through the complex metal lattice. Hence, there would be no wastage of electrical energy in the form of heat.
The Superconductivity was very well explained by the well-known BCS Theory. On cooling certain materials below a certain temperature called Transition temperature or Critical temperature $T_c$, three changes happen in a material which makes it a superconductor. Its resistivity becomes absolute zero. Its conductivity becomes Infinity. It's perfectly diamagnetic and excludes Magnetic flux lines (as a result of Meissner Effect). Hence none of your forces are emitted from superconductors. They always repel magnets (i.e) They develop a magnetic polarity opposite to that of the applied field and hence, they don't allow magnetic fields to pass through them.
The following is multiple choice question (with options) to answer.
Superconductors are materials with a resistivity of? | [
"high magnitude",
"greater density",
"zero",
"above zero"
] | C | 34.6 High-temperature Superconductors Superconductors are materials with a resistivity of zero. They are familiar to the general public because of their practical applications and have been mentioned at a number of points in the text. Because the resistance of a piece of superconductor is zero, there are no heat losses for currents through them; they are used in magnets needing high currents, such as in MRI machines, and could cut energy losses in power transmission. But most superconductors must be cooled to temperatures only a few kelvin above absolute zero, a costly procedure limiting their practical applications. In the past decade, tremendous advances have been made in producing materials that become superconductors at relatively high temperatures. There is hope that room temperature superconductors may someday be manufactured. |
SciQ | SciQ-1099 | thermodynamics, pressure, evaporation
Why can the oven temperature reach $350 {}^\circ\text{F}$ when the maximum temperature of steam at $1 \text{ atm}$ is $212{}^\circ\text{F}$? Is it because the air molecules are able to heat up beyond what the water molecules can? Or are both at the same temperature? 350 °F are 176 °C, which is well above the boiling point of water; Liquid water can not get hotter than 100 °C at 1 atm. However, gaseous water (Steam) can become much hotter.
The oven can only hold around 1 atm; at the point where it exceeds this pressure in the inside, the mixture of gases will stream out of it in the respective proportions.
So what will happen is that during the heating process, air will exit the oven. as more and more water evaporates, this air will contain more and more water (which you will probably see condensing above the oven) according to the increasing amount of gaseous water in the oven.
When the 350°F are reached and the water amount in the air will reach your 598 g/m³, there will be less air and water leaving the oven, as some of the water condenses back into the puddle on the tray, but as long as you keep the pressure constant by allowing the water to escape, this will be vanishingly less and most of it will escape the oven. As long as there is liquid water on the tray, this water will have 100 °C, the air/water mixture in the oven will have 350 °F and the amount of gaseous water in the oven will be around 598g/m³. The water molecules in the air will approximately have the same kinetic energy as the air molecules; as most of the air molecules are heavier, the water will be accordingly faster. This will increase the heat conductivity in the oven, heating the food faster; if you shove your sourdough into the oven, water will condense on its surface too, giving the energy which was used to evaporate the water (which is a lot compared to similar substances!) to the loaf and heating it even faster, yielding a delicious crust. Enjoy it ;)
Edit; The density of 598g/m³ seems to be the density of pure steam at 100°C. Due to thermal expansion, I would expect it to be less at 180°C.
The following is multiple choice question (with options) to answer.
What affects how high a cake rises when it bakes? | [
"air movement",
"air pressure",
"air currents",
"current pressure"
] | B | Air pressure affects how high a cake rises when it bakes. Directions for cake mixes often have special high altitude instructions, like those on the label below. Explain why. |
SciQ | SciQ-1100 | electrons, nuclear-physics, radiation, radioactivity, neutrons
Title: Can we uniquely determine the particles emitted in a neutron induced binary fission of a radioactive element?
Can we uniquely determine the particles emitted in a neutron induced binary fission of a radioactive element?
The following is multiple choice question (with options) to answer.
Binary fission is an example of which type of production? | [
"primitive",
"sexual",
"algal",
"asexual"
] | D | Binary fission is a type of asexual reproduction. It occurs when a parent cell splits into two identical daughter cells. This can result in very rapid population growth. For example, under ideal conditions, bacterial populations can double every 20 minutes. Such rapid population growth is an adaptation to an unstable environment. Can you explain why?. |
SciQ | SciQ-1101 | geophysics, earth-history, geomagnetism, paleomagnetism
Title: How did the intensity of Earth's magnetic field change through geological time? Looking at the wikipedia article on the Earth's magnetic field, I see that its strength varies through time. How did Earth's magnetic field change throughout its history, from the beginning of the Archean period (~4 billions years ago) to today?
My current attempt
All I found so far is this graph from wikipedia (which is on a too short time scale) and this kind of text (not a science paper) reporting an estimate for a given time point (3.2 billions years ago) reporting a field of about 25 microTeslas. The Earth's initial accretion was about 4.5 billion years ago, and there is good Hf-W isotopic evidence that an iron core started to form within about 10 M years, and may have been largely complete within 30 M years. However, the Earth's dynamo, which is driven by isotopic heating and core rotation/convection, didn't switch on strait away. It must have built up over hundreds of millions of years, possibly kick-started by a the magnetic field of a stronger solar wind at that time. The evidence from 3.5 Bn year old dacites suggest that the magnetic field at that time was only 30 to 50% of the current value. There is no magnetic data for 4.4 to 3.5 Bn years, (the time period you are interested in), but current models lean towards lower rather than higher values. There appears to be no mechanism for strong magnetism in the early Earth. Geomagnetic evidence from about 2.5 Bn years ago seems to indicate that the Earths magnetism was more stable then than now, with few if any peaks of high or low magnetism. Probably the Earth's early magnetic field will always be imprecisely known because nearly all the early rocks have been 'cooked' in such a way as to extinguish the early magnetic evidence.
The following is multiple choice question (with options) to answer.
What type of field does earth have? | [
"magnetic",
"atmospheric",
"seismic",
"force field"
] | A | Earth has a magnetic field ( Figure below ). The magnetic field has north and south poles. The field extends several thousand kilometers into space. Earth’s magnetic field is created by the movements of molten metal in the outer core. |
SciQ | SciQ-1102 | conformers, energy
I do not think there is free rotation around the bond indicated in red, because one can write a resonance structure with significant reasonable weight where a double bond would be located between the two groups.
However, how can I go further than that and qualitatively describe the energy barrier for the rotation. I have found (here and there) that in the case of benzoates, the barrier is in the range 3–6 kcal/mol. Should I expect it to be higher or lower in the above molecule? One of way to answer this question is to put it in some QM software. The system is small enough and has higher symmetry so computations shouldn't take to long, even on an older computer.
For co-planar geometry the energy calculated at B3LYP/6-31G(d,p) is –492.132206748 a.u.
The geometry with dihedral angle of 90° between $\ce{CO2}$ and $\ce{C3N2}$ is –492.116719625 a.u. That makes roughly 41 kJ/mol (10 kcal/mol).
Now if you really want to be sure if that's the right energy you should make frequency calculations on both structures to find out if they are minima or transition states. This can take a bit longer (I haven't done it) and I would expect that the better structure (with lower energy) should have no imaginary frequencies and the higher one should have one (TS). If by some accident both of them are minima than TS has probably a dihedral angel somewhere around 45°.
Of course this is only computation. It gives as clues but not the exact answer. You can go for higher level of theory, add solvent modelling and... or you can take your compound and try to make temperature depending NMR spectra. With a bit of luck you can freeze your TS and find out how high is your barrier.
p.s.
It would be good if you mention in your post what tools (in this case computational) are available to you. I really would prefer to explain how to get the number instead of giving just dry answer.
The following is multiple choice question (with options) to answer.
Single bonds allow the atoms they join to rotate freely about the what? | [
"bond axis",
"nucleus",
"atomic orbit",
"electron shell"
] | A | |
SciQ | SciQ-1103 | climate-change, oceanography, paleoclimatology, paleontology, climatology
As abundant as they are in living form, diatoms are generally poorly (and unreliably) preserved in an older oceanic fossil record. Importantly, they evolve rather quickly making tracking chemical changes in a single species over time and space impossible. Bulk chemistries may be obtained from fossilized silicic masses and serve as rough indicators of overall diatom abundance and thus system health.
They are, however, used in novel ways: some diatoms live exclusively in sea ice and can be used to assess duration and distribution of that sea ice, itself a record of sea surface temperature (SST):
Diatoms in Arctic regions: Potential tools to decipher environmental changes
SIDEBAR. Diatoms as Sea Ice Proxies
By contrast, forams are well preserved in the fossil record, have a well calibrated evolutionary record, and as carbonates, contain important isotopes whose ratios are sensitive to SST.
The following is multiple choice question (with options) to answer.
Preserved remains or traces of organisms that lived in the past are known as what? | [
"skulls",
"fossils",
"archives",
"deposits"
] | B | Fossils are preserved remains or traces of organisms that lived in the past. Most preserved remains are hard parts, such as teeth, bones, or shells. Examples of these kinds of fossils are pictured in Figure below . Preserved traces can include footprints, burrows, or even wastes. Examples of trace fossils are also shown in Figure below . |
SciQ | SciQ-1104 | experimental-chemistry, green-chemistry
why are scientist more concerned about fossil fuel instead of CFC?
As commented by LDC3 The production of the more hazardous CFC's has been banned.
There are 95 derivatives of chloro and bromo fluorocarbon which are listed as ODS(Ozone Depleting Substances).
On 16th September, 1987 93 countries sign Montreal Protocol and accept not to use ODS.
Reference: GSEB textbook pdf
The following is multiple choice question (with options) to answer.
Co 2 , h 2 o, methane, o 3 , nitrous oxides (no and no 2 ), and chlorofluorocarbons (cfcs) are known as what type of gases? | [
"chemical gases",
"carbonate gases",
"greenhouse gases",
"hydrogen gases"
] | C | Greenhouse gases include CO 2 , H 2 O, methane, O 3 , nitrous oxides (NO and NO 2 ), and chlorofluorocarbons (CFCs). All are a normal part of the atmosphere except CFCs. The table below shows how each greenhouse gas naturally enters the atmosphere ( Table below ). |
SciQ | SciQ-1105 | everyday-chemistry, toxicity
Such oxidation reactions are catalyzed both by soluble metals such as iron and by light. Hydrogen sulfide also can combine with metals such as iron (Fe++) to precipitate as black iron sulfide (Figure 1 bottom; FeS and FeS2).
The following is multiple choice question (with options) to answer.
A black solid by itself, this element is incredibly important because of what it makes when it combines with many other elements, including oxygen? | [
"hydrogen",
"carbon",
"dioxide",
"lead"
] | B | Carbon is an element. By itself, it’s a black solid. You can see a lump of carbon in Figure below . Carbon is incredibly important because of what it makes when it combines with many other elements. Carbon can form a wide variety of substances. For example, in the air, carbon combines with oxygen to form the gas carbon dioxide. |
SciQ | SciQ-1106 | planets
Title: What is Venus's core made of? As we all know Venus's surface is so hot that it can probably melt lead.
What would be in it's in core?
Is it in the liquid or solid state?
What would be it's temperature?
How many cores does it have? Scientists think that Venus' internal structure is somewhat like Earth's, as shown below:
In other words, a crust, mantle, and core. The evidence points to Venus not having plate tectonics like Earth or a magnetic field. Venus also probably has a partially molten core, like Earth, as it has been cooling at the same rate.
Honestly, we don't know much else. We can tell you the atmosphere composition, but we don't know what the core is made up of. The Venus Wikipedia page (here) is very helpful and has more information and explanations of why we don't know these things.
The following is multiple choice question (with options) to answer.
Radar maps of venus show that it has mountains, canyons and volcanoes surrounded by plains of what? | [
"grasses",
"helium",
"water",
"lava"
] | D | Radar maps of Venus show that it has mountains, canyons and volcanoes surrounded by plains of lava. |
SciQ | SciQ-1107 | 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.
Bones are part of which body system? | [
"circulation system",
"hard system",
"skeletal system",
"muscular system"
] | C | The brain and spinal cord are protected within bones of the skeletal system, but injuries to these organs still occur. With mild injuries, there may be no lasting effects. With severe injuries, there may be permanent disability or even death. |
SciQ | SciQ-1108 | human-biology, biochemistry, metabolism, food
Which seem to go in different, rather contradictory directions.
Also, Studies partially supporting either viewpoint can be found:
Study considering hemoglobin A1c levels
Study considering peak glucose levels
Study considering snacking
Which leaves the non-biologist asking themselves which is the "major effect" (certainly, there will be some truth to each position, but the question is which one(s) got the "main point"), and if there are any other important effects to be considered, hence this broad question here, so I understand, from a biological standpoint, what happens to the carbohydrates when I eat them, so I can conclude for myself how to adapt my diet for "optimal" health. Scope of Answer
The original poster provided ample context for his question, which related to health considerations. It was perhaps for this reason, among others, that the question had not received an answer at the time of writing: questions relating to medical or health advice are off-topic here. However, his actual question is primarily biochemical:
What are the biological differences between the digestion of sugar and
different types of carbs as constituents of different types of food in
humans?
Although this might be answered with a little internet search, I felt it would be hospitable if someone offered him an answer to this — and this only.
Definitions
The basic sugar unit is a mono-saccharide, those of relevance to this question being hexoses or pentoses, having six or five carbon atoms, respectively.
What in non-technical language is called sugar, refers to a specific molecule, sucrose, which is a disaccharide of covalently-bonded glucose and fructose.
What in non-technical language are referred to as dietary carbohydrates generally refers to the storage polysaccharide of plants such as potato and other root vegetables, rice, and other cereal crops used to make bread. This is a homo-polymer composed solely of glucose units.
Summary of the differences in metabolism
Arising from these definitions, the following differences in metabolism emerge:
Different enzymes (amylase for these polysaccharides, sucrase for saccharose) are used to catalyse the hydrolysis of the linkages between the monomeric units.
Absorption in the gut is different for glucose and fructose, as is transport into cells.
The following is multiple choice question (with options) to answer.
Name the 2 types of carbohydrates? | [
"simple and complex",
"simple and nuclear",
"simple and structural",
"simple and thermal"
] | A | Carbohydrates are nutrients that include sugars, starches, and fiber. There are two types of carbohydrates: simple and complex. Pictured below are some foods that are good sources of carbohydrates ( Figure below ). |
SciQ | SciQ-1109 | 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.
The lungs are a series of ever-narrowing tubes that end in a myriad of tiny sacs called what? | [
"testes",
"glands",
"brachii",
"alveoli"
] | D | Breathing certainly is a major contribution to your health! Without breathing, we could not survive. Curiously, the act of breathing itself is little more than an application of Boyle’s law. The lungs are a series of ever-narrowing tubes that end in a myriad of tiny sacs called alveoli. It is in the alveoli that oxygen from the air transfers to the bloodstream and carbon dioxide from the bloodstream transfers to the lungs for exhalation. For air to move in and out of the lungs, the pressure inside the lungs must change, forcing the lungs to change volume—just as predicted by Boyle’s law. The pressure change is caused by the diaphragm, a muscle that covers the bottom of the lungs. When the diaphragm moves down, it expands the size of our lungs. When this happens, the air pressure inside our lungs decreases slightly. This causes new air to rush in, and we inhale. The pressure decrease is slight—only 3 torr, or about 0.4% of an atmosphere. We inhale only 0.5–1.0 L of air per normal breath. Exhaling air requires that we relax the diaphragm, which pushes against the lungs and slightly decreases the volume of the lungs. This slightly increases the pressure of the air in the lungs, and air is forced out; we exhale. Only 1–2 torr of extra pressure is needed to exhale. So with every breath, our own bodies are performing an experimental test of Boyle’s law. |
SciQ | SciQ-1110 | physiology, ichthyology
Salmon use to deal with the NaCl fluxes driven by the gradients between the salmon and its surroundings. In their gill epithelial cells, salmon have a special enzyme that hydrolyzes ATP and uses the released energy to actively transport both Na+ and Cl- against their concentration gradients. In the ocean, these Na+-Cl- ATPase molecules 'pump' Na+ and Cl- out of the salmon's blood into the salt water flowing over the gills, thereby causing NaCl to be lost to the water and offsetting the continuous influx of NaCl. In fresh water, these same Na+-Cl- ATPase molecules 'pump' Na+ and Cl- out of the water flowing over the gills and into the salmon's blood, thereby offsetting the continuous diffusion-driven loss of NaCl that the salmon is subject to in fresh water habitats with their vanishingly low NaCl concentrations.
Reference
Reference
The following is multiple choice question (with options) to answer.
Fish and other aquatic organisms use gills to capture dissolved what? | [
"food",
"oxygen",
"sulfur",
"nitrogen"
] | B | Gases are also capable of dissolving in liquids. There are many examples of this in our everyday lives. For example, carbonated beverages contain dissolved carbon dioxide. We notice this when bubbles come out of solution when the beverage is opened. Another example is when oxygen from the air we breathe dissolves in our blood, where it is transported throughout the body. Fish and other aquatic organisms use gills to capture dissolved oxygen from their environments. |
SciQ | SciQ-1111 | evolution, brain, development
Title: Why does it take so long for the human brain to develop from an evolutionary point of view?
I have read that it takes about 25 years for the brain to be fully developed.
Coincidentally, humans from the Neolithic and Bronze Age had a very short life expectancy, in fact most of their life their brain wasn't fully developed.
My question is:
from an evolutionary point of view, is there a reason why humans spend so much of their life not being fully developed even long after being sexually fully developed? We can say that brain and our nerve system is the first system in embryo that starts to develop and as you said this system is continuing to develop until after birth.
So here is a question that why our brain don't develop completely before the birth ? Evolution has gone so far as to limit the development of the brain in the human embryonic phase and to allow it to continue into the postnatal phase. This helps the infant to be born and ease the birth both for mother and the new born because if the brain had fully grown, the size of the head would have made problem in birth. Now, after birth, the brain continues to grow and develop majorly between ages 2-3 and becomes more mature after that . The ability of the brain to grow over the years gives us the ability to adapt to different environments , learnings and new issues and other capabilities That happens with the subsequent creation and pruning of dendritic spines.
The following is multiple choice question (with options) to answer.
What phase of a human life does not have a definite starting point? | [
"adolescence",
"adulthood",
"childhood",
"death"
] | B | Adulthood does not have a definite starting point. A person may be physically mature by age 16 or 17 but not defined as an adult by law until older ages. In the U. S. , you can’t join the armed forces or vote until age 18. You can’t buy or use alcohol or take on many legal and financial responsibilities until age 21. |
SciQ | SciQ-1112 | evolution, biochemistry, plant-physiology, plant-anatomy, life
Title: Plants without bacteria? is it theoretically possible? I know from school, that all live on the Earth need bacteria as low-level "machines" that break down/extract/convert/produce chemical elements and combinations, other high-level organisms needed. But it is a natural way.
But is it possible to have a world with plants (without mammals or microorganisms and without bacteria) that could exist in the long term. Saying the atmosphere of these world has already enough nitrogen, oxygen and CO2, and of course there is water.
What could break this artificially created world with such conditions (say the world created not from low-level living structures)?
Could bacteria emerge in the world? This is the sort of question that should be considered from more than one perspective. Since this is speculation, take it as a given that there is a lot of 'what if' here.
I doubt most animals and plants can do entirely without bacteria - as you say most of the essential nutrients come from bacteria, who fix nitrogen. If only plants were left on earth, eventually the plants would use up all the nitrogen and they would have to find a way to fix more.
Can bacteria emerge from just a world of plants? I don't think viruses arise spontaneously, but since genomes often have viruses embedded in them, over the course of a billion years or so, its possible since bacteria and viruses continue to be impressed upon our genomes. Would it happen in time? Most would be skeptical whether that timing could work out.
In practice it would be hard to create a world like this. I would be interested to see whether you could sterilize the microorganisms off of seeds without killing the plant for instance. If you're asking about a small sterile environment with only plants, you could do it by adding the nutrients the plants need and giving them sunlight. Such self sustaining systems have been made with cyanobacteria and i'd be surprised if plants could not be included. But these are closed systems and judged by limited amounts of time, so whether this is an answer to your question is not clear. Here it looks like some water plants and fish have been done. If there was a plant that created CO₂ at an adequate rate its possible.
The following is multiple choice question (with options) to answer.
Where do all plants come from? | [
"cetacean ancestors",
"terrestrial ancestors",
"phylogenetic ancestors",
"distant ancestors"
] | B | All plants are adapted to live on land. Or are they? All living plants today have terrestrial ancestors, but some plants now live in the water. They have had to evolve new adaptations for their watery habitat. |
SciQ | SciQ-1113 | human-biology, anatomy
The proportions of diagrams and cross sections of the nasal cavity all seem wildly different. Some of them are just blatantly wrong, depicting, for example, the Eustachian tubes coming from the roof of the nasal cavity instead of the sides. It has been very difficult to find good information on any of this. I am not even sure if I am referring to the region correctly. By nasal cavity, I mean everything between the back of the throat and the posterior nares, although I am aware the nasal cavity includes the region all the way up to the anterior nares as well.
This is the only picture I can find that shows the nasal septum.
This is a better diagram of the rest of the structures. The pharyngeal tonsils are the adenoids. I'm impressed to stumble upon someone who can do that with his tongue. And mainly because I can do that myself!
Looking at the images and feeling with my tongue, this rugged area you mention is definitely too close to the nose to be the adenoids.
So I googled a bit (well, more like a lot) and I found this cool webpage which details that area.
http://www.theodora.com/anatomy/the_pharynx.html
and I found this snippet of text:
Above the pharyngeal tonsil, in the middle line, an irregular
flask-shaped depression of the mucous membrane sometimes extends up as
far as the basilar process of the occipital bone; it is known as the
pharyngeal bursa.
I've found stones in my tonsils but never in my adenoids. What I've sometimes found was dried mucus adhered to it when waking up in the morning.
I believe those stones might be rests of food (which can't really get up there).
Maybe this green mucus you found was just dried mucus? Maybe a little infection on a particular day?
I hope you get the answer, since it's passed a quite long time since you asked :)
The following is multiple choice question (with options) to answer.
The esophagus runs a mainly straight route through the mediastinum of what? | [
"stomach",
"liver",
"lungs",
"thorax"
] | D | Figure 23.13, the esophagus runs a mainly straight route through the mediastinum of the thorax. To enter the abdomen, the esophagus penetrates the diaphragm through an opening called the esophageal hiatus. |
SciQ | SciQ-1114 | human-biology, physiology, cardiology, anatomy
Title: Can humans live without their right atrium? The right atrium is one of four chambers (two atria and two ventricles) in the hearts of mammals (including humans) and archosaurs (which include birds and crocodilians). It receives deoxygenated blood from the superior and inferior venae cavae, the coronary sinus, and the anterior and smallest cardiac veins, and pumps it into the right ventricle through the tricuspid valve.
Can humans survive without right atrium? In this condition blood would fill the right ventricle directly, comparable to some animals like frogs, toads, snakes and lizards. What advantages does the normal human heart have to this anatomy ? If we had this anatomy, where would the best place for pacemakers be, like the sinus node? This is an interesting theoretical question, but several things would need to be clarified:
Does removing the R atrium relocate the SA node to the R ventricle or remove it completely from the picture?
Does the remaining R ventricle have a tricuspid valve?
Technically, the R atrium is the home of the sino-atrial node, which provides natural pacing of the human heart between 60-80 beats/min. Without this natural pacing, our hearts would rely on back-up pacer systems such as atrioventricular node, His-Purkinje systems or the intrinsic but ectopic pacing of individual atrial or ventricular cells.
The following is multiple choice question (with options) to answer.
What chambers are responsible for pumping blood out of the heart? | [
"ventricles",
"vacuoles",
"valves",
"cells"
] | A | |
SciQ | SciQ-1115 | reproduction, endocrinology, pregnancy, ovulation
The decline of the corpus luteum is correlated with a decline in serum levels of ovarian hormones including progesterone, estradiol, and inhibin A. Release from negative feedback provided by these hormones at the level of the hypothalamus and pituitary permits FSH to rise, and the cycle begins again.
You should now be able to see that:
Around the time of ovulation, the uterine lining is not fully developed and is stable due to the hormonal milieu. Menstruation does not occur.
Around the time of menstruation, FSH and LH are suppressed in a way that is not conducive to ovulation.
In theory, yes, of course there would be a lower chance of initiating a viable pregnancy (implantation rather than conception is the most obvious problem) were the endometrial lining to be unstable at the time of ovulation. The problem of luteal phase deficiency is along these lines. In this condition, the corpus luteum does not produce adequate progesterone during the luteal phase to develop the endometrial lining in such a way as to support a healthy pregnancy. However, ovulation and menstruation are still time-separated events for the reasons outlined above.
*Note that the first term is with respect to the endometrium; the second is with respect to the ovary.
Abbreviations:
GnRH - Gonadotropin Releasing Hormone; LH - Luteinizing Hormone; FSH - Follicule Stimulating Hormone
References
1. Anatomy & Physiology, Connexions Web site. Illustration is also from here.
2. Jerome Strauss, Robert Barbieri. Yen & Jaffe's Reproductive Endocrinology. September, 2013. Saunders.
The following is multiple choice question (with options) to answer.
What's the term for the period during which women's ovaries stop producing eggs? | [
"maturity",
"menopause",
"puberty",
"adolescence"
] | B | For most women, menstrual cycles continue until their mid- or late- forties. Then women go through menopause , a period during which their menstrual cycles slow down and eventually stop, generally by their early fifties. After menopause, women can no longer reproduce naturally because their ovaries no longer produce eggs. |
SciQ | SciQ-1116 | paleontology
Title: How to start studying dinosaurs and pre-historic mammals/sea creatures I'm kind new to this hole thing of dinosaurs that I'm really interested in, are there any good books/websites/webpages to study the biology of pre-historic creatures? Dinosaurs, mammals, fishes, anything that is not alive anymore. Also, any good books about the history of how these species evolved and the history behind them would be appreciated. Here's what it takes to really study this: you need to go through the whole bachelor program for geoscientists, that includes fundamental geodynamics like plate tectonics, magmatism, volcanism, volcanic and metamorphic rocks and generally the cycles that make up earth's internal dynamics.
Then there is the huge field of external factors, like sediment geology (that's really complicated stuff), weathering and transport and how soils come to being, diagenesis and the structures sediments can form and their classifications. Role of the ocean (that's where it starts, before all) and the atmosphere, of course.
When through that, usually 4 semesters or so, you can start to specialize. For paleontolgy you need knowledge of earth history, of course, it's subdivision, and the conditions at certain times as far as they are known. Once that's done, then comes real paleontology: Animals (invertebrates and vertebrates), plants, and their development, biological evolution (that's frequently underrated, I find), taphonomy, ... For a sturdy base count another 2-4 semesters.
You may see that even a bunch of websites, maybe all of them together, cannot replace actual study. I am not aware of any site that even gives a reasonable overview of the field. Geoscience, and thus paleontology, touch many fields of natural science.
That said, when asked "How to learn about animal paleontology ?" I allways mention Micheal Benton, Vertebrate Paleontology. It needs a basic understanding of geoscience, evolution and skeleton anatomy. Functional morphology, phylogeny and an overview over sediment geology and earth history also won't harm, but you could give it a try. Some things are explained in between.
The following is multiple choice question (with options) to answer.
What is the set of steps that scientists use to learn about the world? | [
"scientific method",
"philosophic method",
"Socratic method",
"rhythm method"
] | A | Sometime in your life you've asked a question about the world around you. Probably you've asked a lot of questions over the years. The best way to answer questions about the natural world is by using science. Scientists ask questions every day, and then use a set of steps to answer those questions. The steps are known as the scientific method. By following the scientific method, scientists come up with the best information about the natural world. As a scientist, you need to do experiments to find out about the world. You also need to wonder, observe, talk, and think. Everything we learn helps us to ask new and better questions. |
SciQ | SciQ-1117 | evolution
Title: In this representation of the tree of life, what are the lateral connections?
I found this simple representation of the tree of life in a wikipedia article, and I was curious what these horizontal connections shown here are supposed to be, like the ones between plants and protists, or bacteria and protists going to plants. Do they represent things like lateral gene transfer or potential endosymbiotic origin relationships? (like the theory that eucaryotes came from a merging of a bacteria with an archae). Yes, pretty much! Lateral branches here indicate endosymbiotic events and major horizontal gene transfers.
I'd warn though that the diagram is not very accurate, and additions I'd make would complicate it further as a bush (rather than a tree). Each branch root itself is an instance of cladogenesis, and for this reason the diagram is not very accurate (e.g. fungi and metazoans seem to arise within the same "branch"), and also misses a few lateral branches that otherwise exist. My favorite example of atypical horizontal gene transfer is that of prokaryote-insect transfers which occur frequently. This has been known for some time; many insects contain genes of Wolbachia origin and some (not all) are definitively functional, and are understood to facilitate obligate (fully-dependent) mutualisms.
The following is multiple choice question (with options) to answer.
Which are the closest living relations to land plants? | [
"sporozoans",
"charophytes",
"arthropods",
"mammals"
] | B | outcompete the green tint of chlorophyll, making these species appear as varying shades of red. Other protists classified as red algae lack phycoerythrins and are parasites. Red algae are common in tropical waters where they have been detected at depths of 260 meters. Other red algae exist in terrestrial or freshwater environments. Green Algae: Chlorophytes and Charophytes The most abundant group of algae is the green algae. The green algae exhibit similar features to the land plants, particularly in terms of chloroplast structure. That this group of protists shared a relatively recent common ancestor with land plants is well supported. The green algae are subdivided into the chlorophytes and the charophytes. The charophytes are the closest living relatives to land plants and resemble them in morphology and reproductive strategies. Charophytes are common in wet habitats, and their presence often signals a healthy ecosystem. The chlorophytes exhibit great diversity of form and function. Chlorophytes primarily inhabit freshwater and damp soil, and are a common component of plankton. Chlamydomonas is a simple, unicellular chlorophyte with a pear-shaped morphology and two opposing, anterior flagella that guide this protist toward light sensed by its eyespot. More complex chlorophyte species exhibit haploid gametes and spores that resemble Chlamydomonas. The chlorophyte Volvox is one of only a few examples of a colonial organism, which behaves in some ways like a collection of individual cells, but in other ways like the specialized cells of a multicellular organism (Figure 23.24). Volvox colonies contain 500 to 60,000 cells, each with two flagella, contained within a hollow, spherical matrix composed of a gelatinous glycoprotein secretion. Individual Volvox cells move in a coordinated fashion and are interconnected by cytoplasmic bridges. Only a few of the cells reproduce to create daughter colonies, an example of basic cell specialization in this organism. |
SciQ | SciQ-1118 | evolution, zoology, anatomy
Title: Are the transverse septum in sharks and the diaphragm in mammals homologous structures? Are the transverse septum in sharks and the diaphragm in mammals homologous structures?
I have searched on Google Scholar and Web of Science, but haven't found substantial evidence to prove or falsify the claim. A beginning of answer here below, I hope. Please first consider that many structures are involved in the question here, the diaphragm (UBERON:0001103), the diaphragmaticus muscle (UBERON:0036071) and the septum transversum (UBERON:0004161). At Bgee (bgee.org) we aim annotating relations of similarity between anatomical structures, please have a look at our GitHub
https://github.com/BgeeDB/anatomical-similarity-annotations
We already annotated 'diaphragm' as a mammalian structure, not homologous in Amniota (please see https://raw.githubusercontent.com/BgeeDB/anatomical-similarity-annotations/master/release/similarity.tsv). In our next release, you will see the annotation for the 'diaphragmaticus muscle' which is an analog organ in Crocodylians (and Turtles) but not homologous to the mammalian diaphragm either. See here for more details about this new Uberon class:
https://github.com/obophenotype/uberon/issues/1229.
Based on the comments here above, I would say that currently we can argue that there is no evidence for a homologous relationship between the 'septum transversum' in sharks and the mammalian diaphragm. Please note that UBERON:0004161 septum transversum describes the (mammalian) embryonic structure that will give rise to the central tendon of the diaphragm, while here you are talking about a adult structure closer to a 'diaphragmaticus muscle'-like septum, as far as I understand.
But anyway thank you for your interesting question that points out a very exciting and rapidly evolving evo-devo field, as this recent paper also suggests
The following is multiple choice question (with options) to answer.
In vertebrates, what structure runs from the brain to the tail end of the backbone? | [
"aortic valve",
"ribcage",
"backbone",
"spinal cord"
] | D | Vertebrates have a centralized nervous system. As shown in Figure below , the nervous system consists of a brain in the head region. It also includes a long spinal cord that runs from the brain to the tail end of the backbone. Long nerve fibers extend from the spinal cord to muscles and organs throughout the body. |
SciQ | SciQ-1119 | Hey dabaobao ,
When two events are said to be independent of each other, what this means is that the probability that one event occurs in no way affects the probability of the other event occurring. Example - Say you rolled a die and flipped a coin.
Here, no such case is happening. We have two events A and B as well as we have an overlap between them as well Both A and B. Hence, we will use the formula mentioned above. Also, please note that I would not consider A and B independent events unless explicitly stated in the question.
Does that make sense?
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Re: The probability that event A occurs is 0.4, and the probabil [#permalink]
### Show Tags
15 Jun 2018, 11:18
0.6 = 0.4 + PB - 0.25
PB = 0.45
Senior Manager
Joined: 17 Mar 2014
Posts: 451
Re: The probability that event A occurs is 0.4, and the probabil [#permalink]
### Show Tags
21 Jul 2018, 07:28
3
shrive555 wrote:
The probability that event A occurs is 0.4, and the probability that events A and B both occur is 0.25. If the probability that either event A or event B occurs is 0.6, what is the probability that event B will occur?
A. 0.05
B. 0.15
C. 0.45
D. 0.50
E. 0.55
Using Manhattan book formula
Attachments
The following is multiple choice question (with options) to answer.
What is it called when the chance that a certain event will occur? | [
"mutation",
"difficulty",
"procession",
"probability"
] | D | Probability is the chance that a certain event will occur. For example, the probability of a head turning up on any given coin toss is 50 percent. |
SciQ | SciQ-1120 | physical-chemistry
Title: Which is hardest: iron, brass or bone? I was hopping around random wikipedia articles when I came across the article for the Behemoth. In the description for the beast it says:
His bones are as strong pieces of brass; his bones are like bars of
iron
So it got me thinking, which of these three substances is hardest: iron, brass or bone?
(I had a quick look at the Mohs scale, which lists iron as 4, but could not find anything for brass or bone.) These two sources both put bone at a hardness of 5:
http://www.chacha.com/question/how-hard-is-bone-according-to-moh's-hardness-scale
https://answers.yahoo.com/question/index?qid=20110310200841AABwtMj
Whether they are trustworthy is questionable though, so take it as you will.
This source put brass at 3 and iron at 4.5:
http://www.jewelrynotes.com/the-mohs-scale-of-hardness-for-metals-why-it-is-important/
and this image puts brass at 4 and iron at 4-5 (Similar to 4.5):
http://patentimages.storage.googleapis.com/WO2001048807A1/imgf000009_0001.png
While these different sources seem to have conflicting data, I think it would be safe to assume that Brass is the softest of these three materials, Iron comes second, and Bone is the hardest.
Edit: In the description of that monster, the adjective used is 'strong'. You may want to consider how much force each of these materials can withstand instead of how hard they each are :)
The following is multiple choice question (with options) to answer.
What is the hardest of all minerals? | [
"diamonds",
"titanium",
"gold",
"platinum"
] | A | Diamonds like the one pictured in the Figure below are the hardest of all minerals. Is a diamond a crystalline or an amorphous solid? How do you know?. |
SciQ | SciQ-1121 | 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.
When bread bakes, yeast releases which gas? | [
"hydrogen",
"oxygen",
"carbon dioxide",
"carbon monoxide"
] | C | When bread bakes, yeast releases carbon dioxide gas, forming the small holes in bread. The gas was produced by alcoholic fermentation carried out by yeast. |
SciQ | SciQ-1122 | neuroscience, brain
Title: What is in the space between neurons in a brain? When neuron animations are displayed, there are frequently seen neurons, axons arranged in a lattice with a lot of empty space between. I'm interested if there is indeed empty space in the brain, or if it is filled with some sort of fluid? I've checked an article on cerebrospinal fluid but am not sure that it is present all throughout the brain.
The reason I'm asking is that I'm thinking of neurotransmitters- they are released in synapses, but I'm not sure how they stay there - are they suspended in some liquid as well? Not so empty, actually.
The human brain has a mass of ~1.5kg, and volume ~1200cc (a little bigger for men, a little smaller for women). So is heavier than water by a good margin.
While it has Cerebrospinal fluid, that only occupies the subarachnoid space (the space below the skull and above the cortex, contained between two layers: pia matter and arachnoid membrane) and the ventricular system (several spaces inside the brain, remnants of the embryological development of the brain).
Neuron density may vary widely, depending mainly on the particular characteristics of neuron cell types and their interconnections. But besides neurons, there's a lot of infrastructure inside the brain. For example:
Astroglia: They are a type of glial cells which participate in the formation of the blood-brain barrier (supporting the endothelial cells), nourishing of neurons, maintenance of ion and neurotransmitter concentrations, among others. They also keep in place most of the tissue.
Microglia: Small cells with immune (phagocitic) functions inside the brain.
Radial glia: A more specialized precursor cell, that also participates in neuronal migration in the brain.
Oligodendrocites: Cells responsible for the insulation (myelination) of axons.
Neuroepithelial cells: The stem cells in the brain.
The following is multiple choice question (with options) to answer.
What nervous tissue cells play a supporting role to neurons? | [
"axial cells",
"glial cells",
"mammalian cells",
"reissner cells"
] | B | Glial Cells Glial cells, or neuroglia or simply glia, are the other type of cell found in nervous tissue. They are considered to be supporting cells, and many functions are directed at helping neurons complete their function for communication. The name glia comes from the Greek word that means “glue,” and was coined by the German pathologist Rudolph Virchow, who wrote in 1856: “This connective substance, which is in the brain, the spinal cord, and the special sense nerves, is a kind of glue (neuroglia) in which the nervous elements are planted. ” Today, research into nervous tissue has shown that there are many deeper roles that these cells play. And research may find much more about them in the future. There are six types of glial cells. Four of them are found in the CNS and two are found in the PNS. Table 12.2 outlines some common characteristics and functions. |
SciQ | SciQ-1123 | bacteriology, infection
Are there any studies that show the population of V. vulnificus over a time period covering the BP Horizon spill (this happened in April 2010, and oil products are still washing up on beaches in small amounts)
Is it possible that it could be metabolizing oil or other chemicals related to the spill? I found these article, which show exponential increase in population of Vibrio in BP oil spill region (published in 2011 supported in 2013).$^{1,2}$
There is evidence that Vibrio representatives can metabolize oil-derived compounds $^{3,4}$. There is a sizable amount, more than 31%, where found in the Deepwater Horizon Spill.$^5$. Though the reason is still to be proved $in\ vitro$, but studies shows they can persist in the presence of oil.$^6$
Source:
[1]:
High Numbers of Vibrio vulnificus in Tar Balls Collected from Oiled Areas of the North-Central Gulf of Mexico Following the 2010 BP Deepwater Horizon Oil Spill
[2]:
Associations and dynamics of Vibrionaceae in the environment, from the genus to the population level
[3]: West 1984, Numerical taxonomy of phenanthrene-degrading bacteria isolated from the Chesapeake Bay.
[4]: Moxley K., Schmidt S. (2010). Preliminary characterization of an estuarine, benzoate-utilizing Vibrio sp. isolated from Durban Harbour, South Africa. Curr. Res. Technol. Educ. Top. Appl. Microbiol. Microb. Biotechnol. 1249–1254
[5]: Hamdan L. J., Fulmer P. A. (2011). Effects of COREXIT® EC9500A on bacteria from a beach oiled by the Deepwater Horizon spill. Aquat. Microb. Ecol. 63, 101 10.3354/ame01482
[6]: In situ and in vitro impacts of the Deepwater Horizon oil spill on Vibrio parahaemolyticus.
The following is multiple choice question (with options) to answer.
Use of oil-consuming bacteria to clean up an oil spill is an example of what? | [
"bioremediation",
"biodegradation",
"generation",
"coagulation"
] | A | Using Prokaryotes to Clean up Our Planet: Bioremediation Microbial bioremediation is the use of prokaryotes (or microbial metabolism) to remove pollutants. Bioremediation has been used to remove agricultural chemicals (pesticides and fertilizers) that leach from soil into groundwater. Certain toxic metals, such as selenium and arsenic compounds, can also be removed from water by bioremediation. The reduction of − − SeO 24 to SeO 23 and to Se0 (metallic selenium) is a method used to remove selenium ions from water. Mercury is an example of a toxic metal that can be removed from an environment by bioremediation. Mercury is an active ingredient of some pesticides; it is used in industry and is also a byproduct of certain industries, such as battery production. Mercury is usually present in very low concentrations in natural environments but it is highly toxic because it accumulates in living tissues. Several species of bacteria can carry out the biotransformation of toxic mercury into nontoxic forms. These bacteria, such as Pseudomonas aeruginosa, can convert Hg2+ to Hg0, which is nontoxic to humans. Probably one of the most useful and interesting examples of the use of prokaryotes for bioremediation purposes is the cleanup of oil spills. The importance of prokaryotes to petroleum bioremediation has been demonstrated in several oil spills in recent years, such as the Exxon Valdez spill in Alaska (1989) (Figure 13.10), the Prestige oil spill in Spain (2002), the spill into the Mediterranean from a Lebanon power plant (2006,) and more recently, the BP oil spill in the Gulf of Mexico (2010). To clean up these spills, bioremediation is promoted by adding inorganic nutrients that help bacteria already present in the environment to grow. Hydrocarbon-degrading bacteria feed on the hydrocarbons in the oil droplet, breaking them into inorganic compounds. Some species, such as Alcanivorax borkumensis, produce surfactants that solubilize the oil, while other bacteria degrade the oil into carbon dioxide. In the case of oil spills in the ocean, ongoing, natural bioremediation tends to occur, inasmuch as there are oil-consuming bacteria in the ocean prior to the spill. Under ideal conditions, it has been reported that up to 80 percent of the nonvolatile components in oil can be degraded within 1 year of the spill. Other oil fractions containing aromatic and highly branched hydrocarbon chains are more difficult to remove and remain in the environment for longer periods of time. Researchers have genetically engineered other bacteria to consume petroleum products; indeed, the first patent application for a bioremediation application in the U. was for a genetically modified oileating bacterium. |
SciQ | SciQ-1124 | 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.
What is the process called in which living things produce offspring? | [
"reproduction",
"diversification",
"variation",
"photosynthesis"
] | A | All living things are capable of reproduction. Reproduction is the process by which living things give rise to offspring. Reproducing may be as simple as a single cell dividing to form two daughter cells. Generally, however, it is much more complicated. Nonetheless, whether a living thing is a huge whale or a microscopic bacterium, it is capable of reproduction. |
SciQ | SciQ-1125 | python, featurecounts
Title: Help to understand the code for dipeptide composition calculation (in python) Dipeptide composition of a protein sequence is the number of times a particular dipeptide (e.g. Arginine-Histidine) occurs in a sequence divided by the total number of dipeptides in the sequence (which is the length of the sequence - 1)
I have found the following code for this:
import re
def DPC(fastas):
AA = 'ACDEFGHIKLMNPQRSTVWY'
encodings = []
diPeptides = [aa1 + aa2 for aa1 in AA for aa2 in AA]
header = ['#'] + diPeptides
encodings.append(header)
AADict = {}
for i in range(len(AA)):
AADict[AA[i]] = i
for i in fastas:
name, sequence = i[0], re.sub('-', '', i[1])
code = [name]
tmpCode = [0] * 400
for j in range(len(sequence) - 2 + 1):
tmpCode[AADict[sequence[j]] * 20 + AADict[sequence[j+1]]] = tmpCode[AADict[sequence[j]] * 20 + AADict[sequence[j+1]]] +1
if sum(tmpCode) != 0:
tmpCode = [i/sum(tmpCode) for i in tmpCode]
code = code + tmpCode
encodings.append(code)
return encodings
The following is multiple choice question (with options) to answer.
What are the building blocks of peptides? | [
"amino acids",
"alkali",
"magnets",
"rocks"
] | A | A peptide is composed of two or more amino acids. Amino acids are the building blocks of peptides. |
SciQ | SciQ-1126 | forces, gravity, cosmology, solar-system
Title: Would the Moon be able to take water from Earth? I know that if you add mass to the moon, it would get closer to the Earth. We all know that the moon causes the tides because it's gravity pulls the water. So, my question is: If the moon gained more mass and got closer to the Earth, could it have enough pull on the water that it actually pulls it into space? Gravity acts on all matter, not just water (it just so happens that water flows with less resistance than rock) which is why we get noticeable water tides but not very noticeable earth tides. However, if you were to bring a very large gravitating body too close to earth, you would find that the earth isn't quite as solid as it feels.
The answer to your question is yes, but along with the water that would go into 'space', the earth itself would get ripped to shreds by tidal forces bringing large chunks of earth up into 'space' as well, though the name space doesn't really apply here since it's not more of a very messy debris field or accretion disk.
The following is multiple choice question (with options) to answer.
The pull of the moon’s gravity on earth is the main cause of what water phenomenon? | [
"tides",
"waves",
"floods",
"storms"
] | A | The figure below shows why tides occur ( Figure below ). The main cause of tides is the pull of the Moon’s gravity on Earth. The pull is greatest on whatever is closest to the Moon. Although the gravity pulls the land, only the water can move. As a result:. |
SciQ | SciQ-1127 | evolution, mathematical-models, population-biology, population-dynamics, population-genetics
If $p\neq 1/2$ then as long as f(h) = f(m) the system reaches equilibrium at $p = 1/2$ asymtotically. If $p = 1/2$ but f(h) $\neq$ f(m) the asymtotic limit has to be calculated.
See also http://evol.bio.lmu.de/_teaching/evogen/Evo8-Summary.pdf
The following is multiple choice question (with options) to answer.
What happens to evolution when equilibrium is reached within the genes of the population? | [
"it starts over",
"it accelerates",
"it goes backwards",
"it stops occurring"
] | D | If balance, or equilibrium, is to be maintained, there must be no outside influences on the stones. Equilibrium can also be maintained within a population's genes; that means, no evolution can occur. But outside influences usually prevent equilibrium from staying established. |
SciQ | SciQ-1128 | biochemistry, pharmacology, literature, pharmacodynamics
The modulation of the endogenous cannabinoid system, through its metabolite AM404, a compound that inhibits the reuptake of the endogenous cannabinoid/vanilloid anandamide by neurons.
The COX model can explain quite well the action of paracetamol, altought it has been demonstrated an important role of the endocannabinoid system aside of COX. When cannabinoid receptors are blocked with synthetic antagonists, paracetamol's analgesic effects are prevented. This is tought to be due by an active metabolite of paracetamol, that is called AM404 and inhibits the reuptake of anandamide.
Anandamide reuptake lowers synaptic levels of anandamide. This results in a more activated pain receptor (at least the main one, called TRPV1, or according to an old nomenclature: vanilloid receptor). The high levels of anandamine, due to inhibition of its reuptake, desensitise this receptor in a way similar to the capsaicine.
Furthermore, this active metabolite (AM404) inhibits sodium channels, this chemical behaviour is shared with lidocaine and procaine, two common anesthetic drugs.
These two actions by themselves have been shown to reduce pain, and are a possible explanation of paracetamol's mechanism of action; but one other specific activity of this compound remains unexplained by these two models.
Serotonin receptor agonism.
It has been observed that this compound can reduce the social rejection in humans. This can't be explained with COX or type I endocannabinoid system modulation.
Increase of social behavior in mice dosed with paracetamol, wich models a reduction of social rejection response in humansdoes not appear to be due to cannabinoid receptor type 1 activity. .
In the animal model, it seems a result from serotonin receptor agonism.
Aside of this main features, some other evidences are in bibliography.
The following is multiple choice question (with options) to answer.
Prostaglandins worsen what by increasing nociceptor sensitivity to noxious stimuli? | [
"recovery time",
"pain",
"inflammation",
"reaction speed"
] | B | |
SciQ | SciQ-1129 | physiology, cardiology, medicine, electrophysiology, electrocardiography
Title: Why is the current flow shown to be flowing from the negative area towards the positive area? When I was studying the ECG chapter in the book "Guyton and Hall Textbook of Medical Physiology", I noticed something odd in one of the pictures:
As you can see the current is shown to be flowing from the area with a more negative potential towards the area with a more positive potential.
Also here's the part of the text that alludes to the image:
This process provides electronegativity on the insides of the ventricles and electropositivity on the outer walls of the ventricles, with electrical current flowing through the fluids surrounding the ventricles along elliptical paths, as demonstrated by the curving arrows in the figure.
How is this possible? Isn't the current supposed to flow from an area with a higher potential towards an area with a lower potential? By convention, positive current is assumed to be the direction of flow of positive charges. The trouble is that in many common situations (like this one), the current is actually carried by electrons which are negatively charged.
It can be confusing. Blame it on Benjamin Franklin. The convention for current flow was based on his work, before anyone knew about electrons, protons, and ions.
The following is multiple choice question (with options) to answer.
The outer surface of the heart changes from positive to negative during what? | [
"permeability",
"reproduction",
"inflammation",
"depolarization"
] | D | Figure 20.33 The outer surface of the heart changes from positive to negative during depolarization. This wave of depolarization is spreading from the top of the heart and is represented by a vector pointing in the direction of the wave. This vector is a voltage (potential difference) vector. Three electrodes, labeled RA, LA, and LL, are placed on the patient. Each pair (called leads I, II, and III) measures a component of the depolarization vector and is graphed in an ECG. |
SciQ | SciQ-1130 | evolution, trees
Title: How related are trees? I was surprised to see how far apart macadamia and hazelnuts are from each other. I always thought all trees had a common ancestor that was also a tree. But that doesn't seem to be the case? Did wood evolve multiple times? The word "tree" is a not a taxonomic classification, but a human perceptual clustering based on form and size. The word "fish" has a similar problem, covering a vast collection of taxa, some of which are less closely related to one another than they are to us.
Becoming tree-like often has a strong evolutionary value, because plants compete for sunlight and taller plants shade shorter plants. Thus, we should not be surprised that "tree" forms have evolved independently in a number of different lineages.
The common evolutionary lineage for all of these, however, is tracheophyta, the vascular plants. These are plants that have differentiated xylem (which is the wood of a tree) and phloem tissues for transport of water and minerals. Most such plants are not trees, of course, but these tissues provide an effective means of vertical transport and the basis for hard woody material, which appears to have been the key differentiator between plants capable of evolving into trees and plants that are not able do to so.
The following is multiple choice question (with options) to answer.
What are the closest relatives to modern angiosperms? | [
"staurikosaurus",
"mitochondria",
"sporozoans",
"gnetophytes"
] | D | Gnetophytes Gnetophytes are the closest relatives to modern angiosperms, and include three dissimilar genera of plants. Like angiosperms, they have broad leaves. Gnetum species are mostly vines in tropical and subtropical zones. The single species of Welwitschia is an unusual, low-growing plant found in the deserts of Namibia and Angola. It may live for up to 2000. |
SciQ | SciQ-1131 | quantum-mechanics, ideal-gas
Title: How does EM heating cause motion? Similar to how does heating cause motion, I'm trying to understand how a photon imparts motion to an atom, i.e. adds heat to a gas.
I'm going to hazard a guess, and suggest this occurs something along the lines of:
An electron bound to a nucleus absorbs a photon (at a compatible frequency), which causes excitation-return to ground state electronic transition.
I'm guessing* that its this absorption/re-emission(or both) process which imparts momentum.
Can someone correct me/please explain this process in more detail.
(* I can see some issues with this already, but one thing at a time) The first point is that a photon carries momentum, so anything that absorbs it acquires that momentum. So after absorbing a photon a gas molecule/atom will have an increased momentum.
If the atom simply re-emits the photon then the momentum of the atom goes back to what it was before and nothing has changed. Heating occurs when the excited atom collides with some other atom/molecule before it can re-emit a photon, and transfers the extra energy to relative motion of the two atoms. The end result is that the energy in the photon gets converted to kinetic energy of gas molecules.
Response to comment:
In a collision the excited atom may relax into the ground state or another, lower energy, excited state. In the latter case a photon of lower energy could be emitted. I don't know the transition probabilities offhand, but I would guess the collision mostly transfers all the energy of the excited state into kinetic energy and no photon would be re-emitted.
Two atoms in the ground state can collide and electronically excite one of the atoms. If the atom then emits a photon the end result is that the kinetic energy is converted back into the energy of a photon. This is how a gas radiates heat and cools.
The following is multiple choice question (with options) to answer.
Heating a gas gives its particles more of what type of energy? | [
"electrostatic energy",
"residual energy",
"nuclear energy",
"kinetic energy"
] | D | In this lesson, you read that heating a gas gives its particles more kinetic energy. As a result, its volume or pressure also increases. The opposite happens when a gas is cooled. |
SciQ | SciQ-1132 | biochemistry
Another important difference with respect to resulting polymers formed from these bonds - polysaccharides, in contrast to proteins and nucleic acids, form branched as well as linear polymers
α-Amylose is a linear polymer of several thousand glucose residues linked by α(1 >4) bonds. Note that although α-amylose is an isomer of cellulose, it has very different structural properties. This is because cellulose’s β-glycosidic linkages cause each successive glucose residue to flip 180° with respect to the preceding residue, so that the polymer assumes an easily packed, fully extended conformation.
Peptide bond
The resulting linkage formed when α-amino acids polymerize, through the elimination of a water molecule is known as a peptide bond (sometimes called an amide bond):
Peptide bond (shown in red)
Glycosidic bonds between monosaccharide units are the basis for the formation of oligosaccharides and polysaccharides.
The glycosidic bond is therefore the carbohydrate analog of the peptide bond in proteins. (The bond in a nucleoside linking its ribose residue to its base is also a glycosidic bond)
The following is multiple choice question (with options) to answer.
What is the term for long carbohydrate molecules of repeated monomer units joined together by glycosidic bonds? | [
"fibres",
"template strands",
"hydrocarbons",
"polysaccharides"
] | D | Polysaccharides are long carbohydrate molecules of repeated monomer units joined together by glycosidic bonds. A polysaccharide may contain anywhere from a few monosaccharides to several thousand monosaccharides. Polysaccharides are also called complex carbohydrates . Polysaccharides have a general formula of C x (H2O) y , where x is usually a large number between 200 and 2500. Considering that the repeating units in the polymer backbone are often six-carbon monosaccharides, the general formula can also be represented as (C 6 H 10 O 5 ) n , where 40≤n≤3000. |
SciQ | SciQ-1133 | exoplanet
It's probably possible to have volcanic eruptions even though dozens or maybe even hundreds of miles of exotic ice because the heat has to go somewhere, eventually, assing it's likely to build up over time, so either by circulation of eruption, the heat has push through at some point. This even happens on so called "dead" planets like Mars or even the Moon. Mars still has the occasional volcanic eruption, just not very often.
But water worlds certainly can have plate tectonics. There's nothing in the water that would prevent it from happening. Plate Tectonics is, as I understand it, primarily a factor of the size of the planet. Gas planets - different story, but planets with a hard surface, Earth sized, a tiny bit smaller to a fair bit but not much bigger are good candidates for plate tectonics (I think). There's some debate on how large, I think, still going on. But I remember reading that ocean/water worlds might even be more likely to have plate tectonics. Plate tectonics is definitely something we'd look for if we ever get a close enough look at other planets in different solar-systems (exoplanets).
Just my thoughts on this. Not meant to be complete or definitive.
The following is multiple choice question (with options) to answer.
What is the only known planet with large amounts of water? | [
"jupiter",
"earth",
"saturn",
"mars"
] | B | Earth is the third planet from the Sun. It is the only planet with large amounts of liquid water, and the only planet known to support life. Earth is the only inner planet that has a large round moon. |
SciQ | SciQ-1134 | pathophysiology, kidney
Title: To diagnose osteomyelitis of vertebral column in chronic kidney failure Assume you suspect amyloidosis because of the history of the patient: problem with vertebral column and "purulent" (serous, fibrous, or hemorrhagic) inflammation when patient very young.
Now, the patient has a chronic renal failure.
Is there any other method to diagnose the fracture of some bone than röntgen?
Assume you do not know where the fracture is exactly. Osteomyelitis can be diagnosed with the following imaging techniques [1]:
first of all: radiography to view the anatomy of the bone
the sonography can be used to diagnose fluid collections, periosteal involvement. It is also the most useful procedure for kidney assessment [2].
CT is also useful to detect early osseous erosion, but is less sensitive when it comes to bone infection
MRI is the most sensitive and specific for osteomyelitis
Nuclear imaging can be used to identify multifocal osseous involvement.
References:
Carlos Pineda et al., Radiographic Imaging in Osteomyelitis: The Role of Plain Radiography, Computed Tomography, Ultrasonography, Magnetic Resonance Imaging, and Scintigraphy
American College of Radiology, Renal failure
The following is multiple choice question (with options) to answer.
What is the disease in which bones lose mass and become more fragile and likely to break? | [
"fibrosis",
"tuberculosis",
"osteoporosis",
"arthritis"
] | C | Osteoporosis is a disease in which bones lose mass and become more fragile than they should be. Osteoporosis also makes bones more likely to break. Two of the easiest ways to prevent osteoporosis are eating a healthy diet that has the right amount of calcium and vitamin D and to do some sort of weight-bearing exercise every day. Foods that are a good source of calcium include milk, yogurt, and cheese. Non-dairy sources of calcium include Chinese cabbage, kale, and broccoli. Many fruit juices, fruit drinks, tofu, and cereals have calcium added to them. It is recommended that teenagers get 1300 mg of calcium every day. For example, one cup (8 fl. oz. ) of milk provides about 300 mg of calcium, or about 30% of the daily requirement. |
SciQ | SciQ-1135 | organic-chemistry, nucleophilic-substitution, nucleophilicity
Title: Which will give faster SN2 reaction
In $\ce{H2C=CH-Br}$ and $\ce{H3C-CH2-Br}$, which will react faster towards a $\mathrm{S_N2}$ reaction?
According to me, as double bond exhibit −I effect, hence the 1st should do a faster reaction. Am I right, or is there any other reason? $\ce{CH3-CH-Br}$ will give faster $\mathrm{S_N2}$ reaction because when a nucleophile will approach $\ce{CH2=CH-Br}$ for $\mathrm{S_N2}$ reaction the double bond between $\ce{CH2=CH}$ will hinder its approach (steric effect), but there is no such hindrance in case of $\ce{CH3-CH2-Br}$.
To support the answer we can add one more point that in case of $\ce{CH3-CH2-Br}$ the charge $δ^+$ on the $\ce{C}$ atom of $\ce{CH2}$ will be greater in magnitude than that at the $\ce{C}$ atom of $\ce{CH}$ in case of $\ce{CH2=CH-Br}$ because the double bond has better −I effect than single bond, hence it will be easier for $\ce{-Br}$ to attract the shared electron pair towards it and develop a greater $δ^+$ charge on $\ce{C}$ in case of $\ce{CH3-CH2-Br}$, which will ultimately support the approach of the nucleophile for the $\mathrm{S_N2}$ reaction.
The following is multiple choice question (with options) to answer.
What speeds up the reactions of chemical digestion? | [
"stomach acids",
"digestive enzymes",
"protein catalysts",
"electrical enzymes"
] | B | Chemical digestion could not take place without the help of digestive enzymes and other substances secreted into the GI tract. An enzyme is a protein that speeds up a biochemical reaction. Digestive enzymes speed up the reactions of chemical digestion. Table below lists a few digestive enzymes, the organs that produce them, and their functions in digestion. |
SciQ | SciQ-1136 | meteorology, hypothetical, water, geomythology, flooding
Title: Is a complete global flood physically possible on Earth? Genesis 7:11-20 presents an account of an event which, in 40 days, submerges the entire surface of the earth:
[On] the seventeenth day of the second month — on that day
all the springs of the great deep burst forth, and the
floodgates of the heavens were opened…
For forty days the flood kept coming on the earth… all the high
mountains under the entire heavens were covered. The waters rose
and covered the mountains to a depth of more than fifteen cubits
[6.86 m].
Based on this account, my questions are:
Given the amount of water on Earth (including all the water as liquid, solid, and gas, in all possible places: the atmosphere, the surface, and underground), is there enough water to flood the whole earth until ‘all the high mountains… were covered’?
What is the estimated rainfall intensity based on this description, and how intense is it in comparison with today’s rainfall intensity in tropical areas?
Regardless of the veracity or otherwise of the account, this makes for an interesting thought experiment. there is not enough existing water inside this geosystem IMO for such a thing to occur. Let's see these figures here:
One estimate of global water distribution
Oceans, Seas, & Bays 1,338,000,000 -- 96.54% of all water
this figure means that most of the existing water at the global scale is seawater. Sea floor is quite irregular, with some abyss like pits (ex: Mariana trench), up to low water in shallow sea near continents and islands (See figure). A variable topography overall
The following is multiple choice question (with options) to answer.
In how many states does water exist on earth? | [
"three matter states",
"eight matter states",
"two matter states",
"one matter states"
] | A | If water is so simple, why is it special? Water is one of the few substances that exists on Earth in all three states of matter. Water occurs as a gas, a liquid and a solid. You drink liquid water and use it to shower. You breathe gaseous water vapor in the air. You may go ice skating on a pond covered with solid water — ice — in the winter. |
SciQ | SciQ-1137 | optics
Title: How could I translate a field of view value into a magnification value? When I zoom in with Stellarium, it indicates a field of view (FOV) value in degrees, but most binoculars and telescopes are advertised with value like "nX magnification power."
How could I translate this value so I get an idea of what I will see with a telescope or binocular?
For example, I if got a 30X telescope, how much should I zoom to get similar view? Different telescope and binocular eyepieces have different fields of view, so that there is no direct relationship between magnification and field of view.
Eyepieces range in apparent field of view from 30° to 110°, typically being in the range of 50° to 70°. For any given eyepiece, you can calculate the actual field of view by dividing the apparent field of view by the magnification. Thus a 30x eyepiece with a 60° apparent field of view will show you an actual field of view of 60°÷ 30x = 2°.
The following is multiple choice question (with options) to answer.
Find the overall magnification of what instrument by finding the magnification of the objective, then the magnification of the eyepiece? | [
"compound microscope",
"Fixing microscope",
"belt microscope",
"part microscope"
] | A | Example 26.5 Microscope Magnification Calculate the magnification of an object placed 6.20 mm from a compound microscope that has a 6.00 mm focal length objective and a 50.0 mm focal length eyepiece. The objective and eyepiece are separated by 23.0 cm. Strategy and Concept This situation is similar to that shown in Figure 26.16. To find the overall magnification, we must find the magnification of the objective, then the magnification of the eyepiece. This involves using the thin lens equation. Solution The magnification of the objective lens is given as. |
SciQ | SciQ-1138 | dna, zoology, radiation, entomology
1.-3. Therefore, the only sensitive part of insects is the intestinal epithelium which gets renewed on a regular basis (similar to that of humans, also a known target of radiation), but...
Insects (and generally the arthropodes) are known to have exoskeleton. This potentially serves as a good "armor" for vulnerable intestine cells, filtering out the most heavy particles (like alpha- and in some respect also the beta-particles).
EDIT: This seems not to be real protection, see the discussion in comments.
Therefore it is not a surprise that insects generally show much higher resistance against radiation.
EDIT:
As it was correctly added in the comments, there are also gamets, that are most sensitive to radiation (because they bear only the half of the normal genetic information and cannot repair mutations). Even though the lesions in gamets do not lead to immediate death, the potential sterility can easily cause the extinction.
However, cockroaches (and insects generally) are known to be r-animals, meaning that they favor the quantity (r) over quality (K) of their off-spring. This strategy is optimal when dealing with radiation-induced changes in gametes: the high number of offsprings compensates for the genetic imperfections in gametes.
[a] -- meaning that is has secreted peptides in their hemolymph that protect them
[b] -- there are phagocytes, somewhat similar to tissue magrophages in humans, but the rest of the cell chains in immune response in vertrebrates, like T- and B-cells, are completely missing. Those are responsible for the mediation and amplification of the immune response in vertebrates and are the cells that are most susceptible to radiation damage.
The following is multiple choice question (with options) to answer.
Insects have a highly specialized type of respiratory system called what? | [
"tracheal system",
"grunion system",
"gland system",
"nasal system"
] | A | Tracheal Systems Insect respiration is independent of its circulatory system; therefore, the blood does not play a direct role in oxygen transport. Insects have a highly specialized type of respiratory system called the tracheal system, which consists of a network of small tubes that carries oxygen to the entire body. The tracheal system is the most direct and efficient respiratory system in active animals. The tubes in the tracheal system are made of a polymeric material called chitin. Insect bodies have openings, called spiracles, along the thorax and abdomen. These openings connect to the tubular network, allowing oxygen to pass into the body (Figure 39.6) and regulating the diffusion of CO2 and water vapor. Air enters and leaves the tracheal system through the spiracles. Some insects can ventilate the tracheal system with body movements. |
SciQ | SciQ-1139 | water, elements
Title: Chemical composition of seawater Is it true that the sea water is composed of about $86\%$ oxygen, $11\%$ hydrogen and $3\%$ of minerals? The chemical formula of water is $\ce{H2O}$ (two hydrogen and one oxgen) that shows that the number of hydrogen is greater than that of oxygen.
If the number of hydrogen is greater, then why does the sea water consist of $11\%$ hydrogen and $86\%$ oxygen, which is lesser than the oxygen?
The book which I am reading says which is confusing me:
... Seawater is composed of about $86\%$ oxygen, $11\%$ hydrogen and $3\%$ of minerals, consisting mainly of sodium and chlorine. The book that you're reading is measuring by mass.
If you have pure water then you would expect oxygen to make up $\frac{16}{16 + 2}\times 100\% \approx 89 \% $ by mass. Likewise, hydrogen would make up $\frac{2}{16 + 2}\times 100\% \approx 11 \% $ by mass.
The following is multiple choice question (with options) to answer.
What are the two main minerals found in ocean water? | [
"carbon , chloride",
"dioxide , chloride",
"sodium, chloride",
"quartz, carbon"
] | C | Have you ever gone swimming in the ocean? If you have, then you probably tasted the salts in the water. By mass, salts make up about 3.5% of ocean water. The table below shows the most common minerals in ocean water ( Table below ). The main components are sodium and chloride. Together they form the salt known as sodium chloride. You may know the compound as table salt or the mineral halite. |
SciQ | SciQ-1140 | human-biology, biochemistry, metabolism, food
Which seem to go in different, rather contradictory directions.
Also, Studies partially supporting either viewpoint can be found:
Study considering hemoglobin A1c levels
Study considering peak glucose levels
Study considering snacking
Which leaves the non-biologist asking themselves which is the "major effect" (certainly, there will be some truth to each position, but the question is which one(s) got the "main point"), and if there are any other important effects to be considered, hence this broad question here, so I understand, from a biological standpoint, what happens to the carbohydrates when I eat them, so I can conclude for myself how to adapt my diet for "optimal" health. Scope of Answer
The original poster provided ample context for his question, which related to health considerations. It was perhaps for this reason, among others, that the question had not received an answer at the time of writing: questions relating to medical or health advice are off-topic here. However, his actual question is primarily biochemical:
What are the biological differences between the digestion of sugar and
different types of carbs as constituents of different types of food in
humans?
Although this might be answered with a little internet search, I felt it would be hospitable if someone offered him an answer to this — and this only.
Definitions
The basic sugar unit is a mono-saccharide, those of relevance to this question being hexoses or pentoses, having six or five carbon atoms, respectively.
What in non-technical language is called sugar, refers to a specific molecule, sucrose, which is a disaccharide of covalently-bonded glucose and fructose.
What in non-technical language are referred to as dietary carbohydrates generally refers to the storage polysaccharide of plants such as potato and other root vegetables, rice, and other cereal crops used to make bread. This is a homo-polymer composed solely of glucose units.
Summary of the differences in metabolism
Arising from these definitions, the following differences in metabolism emerge:
Different enzymes (amylase for these polysaccharides, sucrase for saccharose) are used to catalyse the hydrolysis of the linkages between the monomeric units.
Absorption in the gut is different for glucose and fructose, as is transport into cells.
The following is multiple choice question (with options) to answer.
Which form of digestion is a purely physical process that does not change the chemical nature of the food? | [
"simple",
"mechanical",
"electromagnetic",
"slow"
] | B | Digestion includes both mechanical and chemical processes. Mechanical digestion is a purely physical process that does not change the chemical nature of the food. Instead, it makes the food smaller to increase both surface area and mobility. It includes mastication, or chewing, as well as tongue movements that help break food into smaller bits and mix food with. |
SciQ | SciQ-1141 | history-of-chemistry
Title: Any false chemical element in history of chemistry? Was there any false chemical element introduced in history of chemistry? I mean a substance that after a while proved that it was not an element. The example that comes to mind is didymium, which turned out to be a mixture of praesodymium and neodymium. The term is still used, as far as I know, to refer to glass doped with a mixture of these lanthanides. This is discussed in one of the 'Chemistry in its element' podcast episodes.
As it turns out, wikipedia has a category called 'Misidentified Chemical Elements'. Especially notable are illmenium, dianium and pelopium, which were all likely mixtures of niobium and tantalum, two rather similar elements.
The following is multiple choice question (with options) to answer.
What was the early study of chemistry called? | [
"alchemy",
"magic systems",
"pharmacology",
"horticulture"
] | A | However, despite this secrecy several contributions were made to modern-day chemistry. Early acids and bases were discovered, and glassware for running chemical reactions was developed. Alchemy helped improve the study of metallurgy and the extraction of metals from ores. More systematic approaches to research were being developed, although the idea of orderly scientific experimentation was not yet well-established. The groundwork was being laid for the development of chemistry as a foundational science. |
SciQ | SciQ-1142 | At some point, all work needs a public airing to improve. That time for me is now. Thank you in advance on behalf of my students for any feedback.
## Chemistry, CAS, and Balancing Equations
Here’ s a cool application of linear equations I first encountered about 20 years ago working with chemistry colleague Penney Sconzo at my former school in Atlanta, GA. Many students struggle early in their first chemistry classes with balancing equations. Thinking about these as generalized systems of linear equations gives a universal approach to balancing chemical equations, including ionic equations.
This idea makes a brilliant connection if you teach algebra 2 students concurrently enrolled in chemistry, or vice versa.
FROM CHEMISTRY TO ALGEBRA
Consider burning ethanol. The chemical combination of ethanol and oxygen, creating carbon dioxide and water:
$C_2H_6O+3O_2 \longrightarrow 2CO_2+3H_2O$ (1)
But what if you didn’t know that 1 molecule of ethanol combined with 3 molecules of oxygen gas to create 2 molecules of carbon dioxide and 3 molecules of water? This specific set coefficients (or multiples of the set) exist for this reaction because of the Law of Conservation of Matter. While elements may rearrange in a chemical reaction, they do not become something else. So how do you determine the unknown coefficients of a generic chemical reaction?
Using the ethanol example, assume you started with
$wC_2H_6O+xO_2 \longrightarrow yCO_2+zH_2O$ (2)
for some unknown values of w, x, y, and z. Conservation of Matter guarantees that the amount of carbon, hydrogen, and oxygen are the same before and after the reaction. Tallying the amount of each element on each side of the equation gives three linear equations:
Carbon: $2w=y$
Hydrogen: $6w=2z$
Oxygen: $w+2x=2y+z$
where the coefficients come from the subscripts within the compound notations. As one example, the carbon subscript in ethanol ( $C_2H_6O$ ) is 2, indicating two carbon atoms in each ethanol molecule. There must have been 2w carbon atoms in the w ethanol molecules.
The following is multiple choice question (with options) to answer.
What are used to balance chemical equations? | [
"fractions",
"coefficients",
"densities",
"velocities"
] | B | Coefficients are used to balance chemical equations. A coefficient is a number placed in front of a chemical symbol or formula. It shows how many atoms or molecules of the substance are involved in the reaction. For example, two molecules of hydrogen would be written as 2H 2 . A coefficient of 1 usually isn’t written. |
SciQ | SciQ-1143 | planet, mercury
Title: How large was Mercury before it shrunk? There's a theory that the reason Mercury has such an enormous iron core is that it was once a much larger planet before it got impacted by an object, resulting in most of its mass getting blasted away. If this theory is true, how large was Mercury before the impact? Could it have been the size of Earth or Mars, or maybe even a super-earth? If we look at the planet's cores and I'm going to ignore liquid vs solid and focus on size overall.
Mars: Core estimated 1,794 +/- 65 km radius. The planet is 3,390 km radius. About 53% of the planet's radius is its core. Mars also has more sulfur in it's core and more Iron in it's mantle than Earth, suggesting that it probably didn't mix as well as Earth did, but I'm not sure that would significantly effect the size of it's core.
Venus: Core estimates have some uncertainty, but by this article, it's core is thought to be about 3,000 km, about 49.5% of it's 6,052 km radius.
Earth's core is about 3,400 km and it's radius 6,371 km, about 53.4% of it's total radius. If we use the 49.5%-53.4% as a guideline, Mercury's 2,440 km radius (85% core, so it's core is about 2,074 KM), so a rough estimate using the other 3 planets as a guideline, 3,880 - 4,190 km radius. That puts it 500-800 km larger than Mars in radius, roughly 2,000 km smaller than Venus in radius.
That's obviously just a rough estimate, but assuming it was similar to the other 3 inner planets, it's probably in that range. I should probably also account for compression. The more massive the planet the greater the compression of it's core, but that would probably only vary a couple percentage points off the estimate and it wouldn't make a big difference.
The following is multiple choice question (with options) to answer.
What kind of core does mercury have? | [
"solid metal",
"dense metal",
"gas",
"liquid metal"
] | D | Mercury is extremely hot and has a liquid metal core. |
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