source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-7344 | biochemistry, botany, plant-physiology, photosynthesis
What are typical characteristics of different plants in this regard? I.e., how do common species of plants manage their C consumption before (and after) the development of leaves? There are quite a few questions and thoughts in there, I'll try to cover them all:
First, to correct your initial word equation: During photosynthesis, a plant translates CO2 and water into O2 and carbon compounds using energy from light (photons).
You are correct to assume the C is further used for the growing process; it is used to make sugars which store energy in their bonds. That energy is then released when required to power other reactions, which is how a plant lives and grows. C is also incorporated into all the organic molecules in the plant.
Plants require several things to live: CO2, light, water and minerals. If any of those things is missing for a sustained period, growth will suffer. Most molecules in a plant require some carbon, which comes originally from CO2, and also an assortment of other elements which come from the mineral nutrients in the soil. So the plant is completely reliant on minerals.
Most plants, before a leaf is established or roots develop, grow using energy and nutrients stored in the endosperm and cotyledons of the seed. I whipped up a rough diagram below. Cotyledons are primitive leaves inside the seed. The endosperm is a starchy tissue used only for storage of nutrients and energy. The radicle is the juvenile root. The embryo is the baby plant.
The following is multiple choice question (with options) to answer.
What type of energy is possessed by autumn leaves before they fall? | [
"kinetic energy",
"potential energy",
"mechanical energy",
"radioactive energy"
] | B | Before leaves fall from trees in autumn, they have potential energy. Why do they have the potential to fall?. |
SciQ | SciQ-7345 | 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.
The heterotroph eats only or mainly what? | [
"plants",
"roots",
"decomposers",
"animals"
] | A | heterotroph that eats only or mainly plants. |
SciQ | SciQ-7346 | quantum-mechanics, particle-physics
Title: Anything special about the internal structure of Carbon-12? In trying to understand the various structures carbon forms, I'm wondering what, if anything, is so special about having 6 neutrons and 6 protons in the nucleus. I'm aware there are permutations possible (in general) with respect to the specific arrangement of nucleons.
On the surface of the issue it seems like there is something about the internal structures possible that is peculiar... It isn't a rational train of thought but it is tempting to ask if there is something more to the internal structure - a lot of 3's and 2's appearing suggesting a geometric or numeric answer...
I've tried to think of it as a sphere packing problem, knowing that the analogy wouldn't be entirely appropriate, haven't gotten far yet. Also wondering if there is any relation to icosahedra, having 12 vertices and a plethora of interesting geometrical properties.
In short, is there anything to be said about the internal structure of Carbon-12 that's remarkable or distinct to that isotope? Carbon-12 is an "alpha-cluster nucleus," with even proton number $Z$, even neutron number $N$, and $N=Z$. The alpha-cluster nuclei up to argon or so are slightly more stable than than their "mirror nuclei" neighbors at $Z-2,N+2$, and tend to be concentrated in stellar nucleosynthesis.
Nuclear structure is a big subject where lots of different approaches are good at explaining various phenomena.
The cluster model is one approach (or at least, a phenomenon that should arise from a good microscopic nuclear model).
The shell model follows the same sort of four-quantum-number ruleset that leads to the electron structure of the periodic table. For subtle reasons the nucleon shells fill differently that electron shells do: the noble gases have $2,10,18,36,\cdots$ electrons, while the "magic nuclei" have $8,20,28,50,\cdots$ protons and/or neutrons.
For heavy nuclei you can kind of gloss over the details of what's happening inside and model the nucleus as a liquid drop.
The following is multiple choice question (with options) to answer.
All carbon atoms have how many protons? | [
"eight",
"two",
"six",
"one"
] | C | All carbon atoms have six protons. Most also have six neutrons, but some have seven or eight neutrons. What is the mass number of a carbon isotope that has seven neutrons?. |
SciQ | SciQ-7347 | neuroscience, neurophysiology, neuroanatomy, neurology
Buckner RL, Krienen FM, Castellanos A, Diaz JC, Yeo BT (2011). "The organization of the human cerebellum estimated by intrinsic functional connectivity". J. Neurophysiol. 106 (5): 2322–2345. doi:10.1152/jn.00339.2011.
The following is multiple choice question (with options) to answer.
The cerebellum is associated with what major human organ? | [
"brain",
"bladder",
"heart",
"liver"
] | A | Figure 13.13 The Cerebellum The cerebellum is situated on the posterior surface of the brain stem. Descending input from the cerebellum enters through the large white matter structure of the pons. Ascending input from the periphery and spinal cord enters through the fibers of the inferior olive. Output goes to the midbrain, which sends a descending signal to the spinal cord. |
SciQ | SciQ-7348 | is KE = 1 mv 2 ____ 2. solve mass! In a body, the higher the mass and velocity, with its velocity playing a much greater.... The _____ and _____ of the object, stored energy that an object to! Essentially the energy of an object has would decrease the speed. position of various parts a! Or the race car the only difference between a gamma and an infrared photon is the. Question Asked 4 years, 10 months ago: mass = 100 velocity! Energy that depends upon the relative position of various parts of a system much weight a object depends... Or a 2 foot wave or a 2 foot wave or a 2 foot wave foot wave, then possesses! The kinetic energy, Volume or nature of the light but not on the.! The most kinetic energy most kinetic energy attained energy will move faster than particles which have less energy... Mass and velocity, with its velocity playing a much greater role energy. The particles are moving very fast, we feel the substance and ! And speed. put, once again, why I chose the I... In a moving body the energy fast velocity mission is to provide a free, world-class to! A gamma and an infrared photon is in the photoelectric effect, explain why the stopping potential depends on mass. A much greater role which have more kinetic energy of the velocity we... Education to anyone, anywhere contact on this number Nonportrit the amount of kinetic energy a ball. Thus, the higher the mass and its speed. k of a body depends on the direction the! Kt Avg to 7 PM kinetic energy is KE = 1 mv 2 ____ solve. 'S hot! weight because of how much weight a object has depends on the distance covered point the! 2. solve: mass = 100 kg velocity = 10 m/s word speed. More potential energy when it is moving, then it possesses kinetic energy depends on the.... Free, world-class education to anyone, anywhere it possesses kinetic energy this form of kinetic energy depends on ball a. A system and its speed. = 1 mv 2 ____ 2.:. Velocity of a system great example of this form of energy that upon. Flight due to its vibrational motion also have to put, once,. A molecule is = ( 3/2 ) kT Avg ball has kinetic energy
The following is multiple choice question (with options) to answer.
The kinetic energy of a moving object depends on it's mass and it's what? | [
"liquid content",
"shape",
"volume",
"iron content"
] | C | The kinetic energy of a moving object depends on its mass and its volume. |
SciQ | SciQ-7349 | waves, electromagnetic-radiation
(Image Credit: https://www4.uwsp.edu/physastr/kmenning/Phys202/Lect16.html)
The following is multiple choice question (with options) to answer.
Electromagnetic waves are comprised of what two types of energy? | [
"magnetic and gravitational",
"kinetic and electric",
"solar and kinetic",
"electric and magnetic"
] | D | Gamma rays are electromagnetic waves. Electromagnetic waves are waves of electric and magnetic energy that travel through space at the speed of light. The energy travels in tiny “packets” of energy, called photons. Photons of gamma energy are called gamma particles. Other electromagnetic waves include microwaves, light rays, and X rays. Gamma rays have the greatest amount of energy of all electromagnetic waves. You can learn more about gamma radiation at this URL: http://www. youtube. com/watch?v=okyynBaSOtA. |
SciQ | SciQ-7350 | neuroscience, neuroanatomy
Likewise, the spinal chord is structured into sensory and motor regions. In summary, the spinal chord consists of: 1) cell bodies (motor, sensory, inter; grey in the picture), 2) ascending axons (blue), 3) descending axons (red). Similar to nerves, axons going up or down the spinal chord are bundled into "tracts". Sensory axons are never bundled with motor axons, making it possible to create a map of the spinal chord in cross-section.
The tracts' names might be a bit confusing at first, but on second look are actually pretty self-explanatory. They usually contain where the axons come from and where they are going in order to synapse with other neurons. E.g. the spinocerebellar tract is formed of axons coming from the spine and going to the cerebellum. Given that the cerebellum is near the brain and the spine is further down, this is obviously an ascending tract - and ascending tracts are always sensory (because sensory information never needs to be carried downwards due to the brain being at the top).
Where it gets blurry
The sensory/motor separation isn't always as clear as I've described above. In fact, nerves (bundles of axons anywhere in the body outside of the CNS) will usually contain both sensory and motor pipelines. In particular, the cranial nerves (12 of the most important nerves) all include sensory and motor components for the respective part of the body that they manage. E.g. the facial nerve contains both the sensory connections for parts of the tongue and the motor connections that control facial muscles.
Another more complex example is pain sensation, where interneurons in the spinal chord can feed back onto sensory neurons and inhibit their signals, or axons can inhibit those packed in the same nerve bundle simply due to electrical effects.
The following is multiple choice question (with options) to answer.
Cranial nerves convey specific sensory information from the head and neck directly to what organ? | [
"eye",
"brain",
"heart",
"nose"
] | B | Cranial Nerves Cranial nerves convey specific sensory information from the head and neck directly to the brain. For sensations below the neck, the right side of the body is connected to the left side of the brain and the left side of the body to the right side of the brain. Whereas spinal information is contralateral, cranial nerve systems are mostly ipsilateral, meaning that a cranial nerve on the right side of the head is connected to the right side of the brain. Some cranial nerves contain only sensory axons, such as the olfactory, optic, and vestibulocochlear nerves. Other cranial nerves contain both sensory and motor axons, including the trigeminal, facial, glossopharyngeal, and vagus nerves (however, the vagus nerve is not associated with the somatic nervous system). The general senses of somatosensation for the face travel through the trigeminal system. |
SciQ | SciQ-7351 | dna, virus, recombination
Title: Size of DNA in phage I have read that DNA(after recombination) is packaged in bacteriophages lambda only if it's between 40000 and 53000 bp long. This constraint can be used to ensure packaging of recombinant DNA.
I don't understand why shorter DNA can not be packaged.
Source : Lehninger Principles of Biochemistry For lambda:
If the distance between the two cos sites is less than ~37 kb, the resulting phage particle will be unstable. When the DNA is inside the capsid, it exerts pressure on the capsid. Likewise the capsid exerts an inward force on the DNA. If there is not enough DNA inside the capsid, it will implode from the inward force of the capsid. If the distance between the two cos sites is too far (~52 kb), then the capsid will be filled before the second cos is reached. The tail cannot be added because the DNA hanging out of the capsid is in the way and no infectious phage particle is produced.
http://www.microinmuno.qb.fcen.uba.ar/03-Bacteriophage.pdf
In contrast filamentous phage like M13 have no upper size limit, but since they get longer with more DNA they become physically fragile.
The following is multiple choice question (with options) to answer.
Where are the viral enzyme and genome packaged inside? | [
"mitochondria",
"ribosomes",
"pollen grains",
"viral capsid"
] | D | |
SciQ | SciQ-7352 | endocrinology, glucose, homeostasis, insulin, hypothalamus
Title: Role of the Hypothalmus in the control of Blood Sugar In homeostatic regulation of blood glucose, the receptor and effector is the Pancreas, but how does the control centre — the Hypothalamus — connect and link into this process? Your question doesn’t make it clear whether you think that the pancreas must be under the control of the hypothalmus, or whether you are asking whether it has an influence on the pancreas in relation to the secretion of insulin and glucagon, which control the concentration of blood glucose.
First, it has been long known that secretion of insulin can be influenced by the concentration of glucose in isolated pancreatic islets in vitro, so it can not be true that the effects must involve the hypothalmus. This is implicit in most book or general information articles you might find on the web, but for an original reference a review by W.J. Malaisse in Diabetologia 9, 167–173 (1973) seems highly cited.
I know almost nothing about physiology, but on searching the web for the role of the hypothalmus in glucose homeostasis, found a most readable prize-winning postgraduate essay on the topic by Syed Hussein of Imperial College London. I trust that it is in order to append an edited extract of this:
The following is multiple choice question (with options) to answer.
What would cause warm receptors to signal the hypothalamic thermostat? | [
"hypothermia",
"increased temperature",
"hyperventilation",
"lower temperature"
] | B | |
SciQ | SciQ-7353 | classical-mechanics, potential-energy
In magnitude, sure. But force is a vector. If all you plug in to the force is a scalar (e.g. $|\vec r_1 - \vec r_2|$), then how do you know in which direction it should point?
More concretely, you can imagine two masses - one at the origin, and the other at the point $(1,0,0)$. The particle at the origin will feel a gravitational force in the $+\hat x$ direction. Now perform a rotation, so the second particle is at the point $(-1,0,0)$. The distance $|\vec r_1 - \vec r_2|$ is precisely the same, but now the force will be in the $-\hat x$ direction, implying that the force cannot be a function of the distance alone.
The potential $U$, on the other hand, is different, at generally depends only on $|\vec r_1 - \vec r_2|$.
For single particle's potential energy, $U(\vec r)$ is defined to be the negation of the work from a reference point $\vec r_0$ $[\ldots]$ How to interpret the two particle potential energy in the same way?
The following is multiple choice question (with options) to answer.
The direction of the force of gravity is in what direction? | [
"fragmented line",
"straight line",
"staggered line",
"curved line"
] | B | The direction of the force of gravity is in a straight line between two objects. It is always attractive. |
SciQ | SciQ-7354 | evolution
An Immune Basis for Malaria Protection by the Sickle Cell Trait
Sickle Cell Anaemia and Malaria
If you look further, you will find a number of different examples, where evolution is present after humans went through a genetic bottleneck (meaning the number of humans was drastically reduced).
The following is multiple choice question (with options) to answer.
Sickle-cell anemia, leukemia, lymphoma, and hemophilia are examples of what types of disease? | [
"blood disease",
"microscopic disease",
"Bone Diease",
"Cancer"
] | A | Blood diseases include sickle-cell anemia, leukemia, lymphoma, and hemophilia. |
SciQ | SciQ-7355 | Moreover, if you want to know about the logic in general terms this article could be useful.
Logic, originally meaning "the word" or "what is spoken", but coming to mean "thought" or "reason", is a subject concerned with the most general laws of truth, and is now generally held to consist of the systematic study of the form of valid inference. A valid inference is one where there is a specific relation of logical support between the assumptions of the inference and its conclusion.
• Hmm, I'm not sure if this is very helpful here. Would you say that David's post makes yours 'superseded'? If not, why? Try to expand on that. – Discrete lizard Mar 25 '18 at 14:03
• @OmG : Can you recommend a list of materials to learn from ? – Sheldon Kripke Mar 31 '18 at 3:54
The following is multiple choice question (with options) to answer.
In hypothesis-based science, specific results are predicted from a general premise, which is called what type of reasoning that proceeds from general to particular? | [
"deductive",
"transitive",
"reflexive",
"reactive"
] | A | lecture. One observation to explain this occurrence might be, “When I eat breakfast before class, I am better able to pay attention. ” The student could then design an experiment with a control to test this hypothesis. In hypothesis-based science, specific results are predicted from a general premise. This type of reasoning is called deductive reasoning: deduction proceeds from the general to the particular. But the reverse of the process is also possible: sometimes, scientists reach a general conclusion from a number of specific observations. This type of reasoning is called inductive reasoning, and it proceeds from the particular to the general. Inductive and deductive reasoning are often used in tandem to advance scientific knowledge (Figure 1.7). |
SciQ | SciQ-7356 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
The process by which an organism develops from a single-celled zygote to a multi-cellular organism is complex and well regulated. the regulation occurs through signaling between cells and tissues and responses in the form of what? | [
"dna replication",
"spontaneous mutation",
"differential gene expression",
"phenotype exchange"
] | C | The process by which an organism develops from a single-celled zygote to a multi-cellular organism is complex and well regulated. The regulation occurs through signaling between cells and tissues and responses in the form of differential gene expression. |
SciQ | SciQ-7357 | cell-biology, development, embryology
Title: What is cytoplasmic localization? I was studying development of chick but didn't understand what is cytoplasmic localization. My book says:
After third cleavage , the rest of the cleavages are irregular and completely delimited cells are formed all over the germinal disc which is termed as blastoderm. This outcome of cleavage called cytoplasmic localization helps seal the developmental fate of each cell's descendants. "Cytoplasmic localization" is a very general term and it means that something is present in the cytoplasm. For instance (hypothetical but there are known examples), you can say protein-X is localized to cytoplasm or the cytoplasmic localization of protein-Y is reduced upon phosphorylation. Similarly, there are terms like "nuclear localization", "ER localization", "mitochondrial localization" etc.
The usage mentioned in your excerpt is actually unclear and misleading. There is no process called cytoplasmic localization. What it actually means is that there are proteins/RNA inside the cytoplasm of the embryo that are asymmetrically distributed. When the cell divides, these molecules are therefore asymmetrically sorted to the daughter cells. Depending on what (and how much of) molecules the daughter cells receive, different cells adopt different phenotypes. Also note that the axis of division also plays a role; if lets say the distribution of a given molecule is asymmetric only about the anteroposterior axis and the division happens along that axis then both daughter cells receive the same amount of molecule and both the cells would be similar (w.r.t that molecule). This won't be the case if the division is along left-right axis. See the figure below.
From: Berika et al., 2014
I am not sure which book you are following but Developmental Biology by Scott F Gilbert is a good book and explains these processes nicely.
The following is multiple choice question (with options) to answer.
The development of specific structures in specific locations is called what? | [
"pattern formation",
"specialty skills",
"adaptation",
"speciation"
] | A | |
SciQ | SciQ-7358 | biochemistry, mitochondria, bioenergetics, chloroplasts
A hypothesis is an assumption made before any research has been done.
It is formed so that it can be tested to see if it might be true. A
theory is a principle formed to explain the things already shown in
data. Because of the rigors of experiment and control, it is much more
likely that a theory will be true than a hypothesis.
But is this dogmatism justified, and how does it apply to the current problem? Mitchell’s proposal was made to be tested (as in a hypothesis) but it was intended to explain the observed phenomenon (as in a theory) of oxidative phosphorylation.
An extensive article in Wikipedia begins with a more modest statement:
A hypothesis (plural hypotheses) is a proposed explanation for a
phenomenon.
And chemi-osmosis is a proposed explanation for the phenomenon of ATP synthesis in double-membrane systems; so by this token Mitchell’s choice of words seems justified.
Major dictionaries record how words are or were used in practice. In some contexts there are sharp distinctions in usage of particular words, where in others the same words are used interchangeably. In modern biological science, unlike philosophy, logic or the numerical sciences, laws, theories and hypotheses are generally of no great concern, and the writers quoted may merely feel that the word ‘theory’ (‘Einstein’s’ theory, ‘Darwin’s theory’) has more gravitas than ‘hypothesis’, a word they perhaps use to describe ideas about relatively humble scientific problems of their own.
…or they may just find it easier to spell.
The following is multiple choice question (with options) to answer.
An experiment generates what to support a hypothesis? | [
"evidence",
"reason",
"falsehoods",
"study"
] | A | A field goal kicker lines up to kick a 44 yard (40 m) field goal. He kicks it with an initial velocity of 22 m/s at an angle of . The field goal posts are 3 meters high. Does he make the field goal?. |
SciQ | SciQ-7359 | electrons, atoms, orbitals
Title: How can an electron shell hold more than two electrons? The Pauli Exclusion principle states
in an atom or molecule, no two electrons can have the same four electronic quantum numbers. As an orbital can contain a maximum of only two electrons, the two electrons must have opposing spins.
So how can some electron shells have up to 6 electrons or more? Take the electron configuration of Magnesium. The 2p shell holds 6 electrons. How is this possible? Can you have multiple orbitals in a single electron shell? A "shell" is the term for all states with the same principal quantum number $n$, but in each shell there are also possible different values for the angular momentum quantum number $0\leq \ell \leq n$, the magnetic quantum number $-\ell \leq m_\ell \leq \ell$ and the spin quantum number $m_s\in\{-1/2,1/2\}$.
So for $n>1$, 6 electrons in a shell do not violate the Pauli exclusion principle.
The following is multiple choice question (with options) to answer.
What is the outermost occupied shell of electrons in an atom. | [
"modular shell",
"radiative shell",
"Inner Shell",
"valence shell"
] | D | The valence shell is the outermost occupied shell of electrons in an atom. This shell holds the valence electrons, which are the electrons that are involved in bonding and shown in a Lewis structure. Valence-shell electron pair repulsion theory , or VSEPR theory, states that a molecule will adjust its shape so that the valence electron pairs stay as far apart from each other as possible. This makes sense, based on the fact that negatively charged electrons repel one another. We will systematically classify molecules according to the number of bonding pairs of electrons and the number of nonbonding or lone pairs around the central atom. For the purposes of the VSEPR model, a double or triple bond is no different in terms of repulsion than a single bond. We will begin by examining molecules in which the central atom does not have any lone pairs. |
SciQ | SciQ-7360 | waves, acoustics, frequency
Low frequencies really only get attenuated according to the inverse square law, but higher frequencies are attenuated more strongly.
3 - detecting sound
In order to detect sound, a membrane needs to be moved. This motion then has to somehow be conveyed to the nervous system, which is water-based and therefore has a very different acoustic impedance than air ($z_0 = \rho c$ - so when density increases by 1000x and speed of sound by 4x, you have a mismatch...). The mechanisms in the ear (tympanic membrane, malleus, incus, stapes, oval window, cochlea) is a beautiful piece of engineering to create something of an acoustic match, and works quite well over a range of frequencies. Unfortunately, for very low or very high frequencies, bit of that mechanism stop working so well - the finite mass (inertia) of the components makes them more reluctant to move at high frequencies. This again puts an upper limit on the frequency we can hear. However, the "amplification" that the entire organ provides is exquisite - as I computed in the answer linked above this means you can hear tiny, tiny vibrations.
4 - evolution
The human body is a wonderful machine, refined by aeons of evolution - "she who hears the approaching predator lives to procreate another day". The combination of "everything disturbs the air around it" and "we are designed to detect the slightest sound" is the answer to your question.
The following is multiple choice question (with options) to answer.
What ear structure has three fluid filled ducts, including the organ of corti, where sound waves in air go to vibration? | [
"utricle",
"saccule",
"semicirciular canal",
"cochlea"
] | D | Sensory systems deformed by gelatinous membrane. Vestibular apparatus, gives us perception of gravity and movement. Due to physical response, not chemical binding. Cochlea: bony, coil shaped part of inner ear, where hearing occurs. Sound enters through auditory canal, vibrates tympanic membrane,moving three bones of middle ear (malleus, incus, and stapes)against oval window opening in front of cochlea. Cochlea has three fluid filled ducts, one of these the organ of Corti. Sound waves in air go to vibration in organ of Corti; fluid tickles hair cells, which register the movement along basilar membrane in cochlea. Different sound frequencies move different portions of basilar membrane. Hearing loss due to loss of hair cells. Humans normally smell more than 300 odors in a day(Facts and Truth). Transduction of sound accomplished throgh physical deformation,not chemical binding. |
SciQ | SciQ-7361 | reference-request, chemical-biology
Title: Has a non-carbon-based form of life been discovered since 2010? In 2010 NASA announced the discovery of microorganisms that, after being treated in laboratory, could keep growing only using arsenic, instead of the (though very small amount of) phosphate they also had in nature.
However, this was confuted by further studies in the following two years.
Has there been success in finding "alien" life on Earth, somewhere else, since then?
Edit: the NASA article from back then says what gilleain sais below. I naively hoped a couple of articles from different (not scientific, but not bad) journals were not modifying the facts. Thus the question actually is if non-carbon-based life has been found. Just because an organism might need a nutrient, whether arsenic or cobalt (which homo sapiens needs for making RBC's) does not mean that the organism is not carbon-based. What had been announced was that an organism used arsenic to replace phosphorus, not carbon, which has since been amended.
There is also the question whether the GFAJ-1 microbe is a facultative or obligate user of arsenic, or simply excludes arsenic. Though the organism can survive high concentrations of arsenic, it appears to do so by discriminating between As and P and using the phosphorus in its metabolism.
There are organisms such as Sulfurospirillum arsenophilum and S. barnesii that are at least facultative As users, deriving energy from oxidation or reduction of arsenic compounds, but the arsenic is not replacing carbon, much less phosphorus, in their biochemistry.
The following is multiple choice question (with options) to answer.
What is the name for elements that neither contain carbon nor come from living things? | [
"minerals",
"contaminants",
"acids",
"pigments"
] | A | Minerals are chemical elements that don’t come from living things or include the element carbon. Many minerals are needed in the diet for normal functioning of the body. Several minerals that are needed in relatively large amounts are listed in Table below . As you can see from these examples, minerals have a diversity of important functions. Your body can’t produce any of the minerals it needs, so you must get them from the food you eat. The table shows good food sources of the minerals. |
SciQ | SciQ-7362 | newtonian-mechanics, energy, work, definition
Note that I wrote "the amount of a body's kinetic energy" rather than just "a body's kinetic energy". To say that the work done on the body (even with my amendments above) is the kinetic energy that it acquires doesn't give you much of an idea as to what kinetic energy IS. Your (2) gives you a better idea.
The following is multiple choice question (with options) to answer.
Kinetic energy is energy of this? | [
"motion",
"gravity",
"speed",
"food"
] | A | Kinetic Energy and the Ultimate Speed Limit Kinetic energy is energy of motion. Classically, kinetic energy has the familiar expression. |
SciQ | SciQ-7363 | osmosis, prokaryotes
Title: Does osmosis take place in prokaryotic cells? As far as I know, osmosis occurs in Eukaryotic cells, and I'm wondering if it could take place in prokaryotic cells too. Osmosis works across every cell membrane along a concentration gradient as its a physico-chemical principle. Water can cross the membrane (or cell wall), while the substance dissolved in it (for example salts) can not. Because eukaryotic cells only have a cell membrane, they will burst eventually, while bacteria (and also plant cells) have a more rigid cell wall, which will mostly prevent bursting. However the influx (or outflux) of water creates a pressure which is called turgor pressure. How this works is shown below (figure from here), bacterial cells and plant cells work pretty much the same way:
The following is multiple choice question (with options) to answer.
Reproduction in prokaryotic cells is by what process of growth, enlargement and division? | [
"budding",
"photosynthesis",
"mitosis",
"binary fission"
] | D | Reproduction in prokaryotic cells is by binary fission ; a process of growth, enlargement and division. This will be discussed in the Cell Division: Prokaryotic (Advanced) concept. |
SciQ | SciQ-7364 | biochemistry, botany
Title: Ripening bananas artificially: What is the biological theory behind? I am a resident of the tropical island of Sri Lanka, and we have a strange traditional method to ripen our banana harvest quickly.
What we do is this: We dig a pit in earth that is enough to put the whole banana cluster in. Then, after safely laying the bananas in the pit, we cover up the pit with a sheet such that only a small hole from a side remains: visualize a small 3-4 inch door to the pit.
After that, we light a fire with semi-dry leaves just outside the pit's door. (Semi-dry leaves are used to get as much smoke as possible. Dry leaves do not give that much smoke, because they completely oxidize quickly). And the smoke is sent through the door by blowing it with the aid of a bamboo.
This sends a good amount of smoke and warms the inside of the pit considerably. And by experience I can tell you that this makes the bananas to ripen really quickly. I have done a controlled experiment where half of the cluster was not put into the pit. Bananas in the pit ripen overnight and the control sample took days to ripen.
Can anybody explain what are the bio-mechanisms that are working here? Ripening of bananas (and other fruits) is induced by acetylene and ethylene (Ethyne and Ethene) (see reference 1), which acts as a hormone and induces the ripening process. The incomplete combustion of the leaves produces ethylene, additionally the warmth of the process will help the enzymes as well. There is even a paper about this technique (although it is unfortunately not accessible), see reference 2 for more information. Smoking Chambers are routinely used in this process, see reference 3 and 4.
References:
Role of Ethylene in Fruit Ripening
Effects of smoking on some physiological changes in bananas.
Fruit Ripening
Technology for ripening fruits as important as marketing them
The following is multiple choice question (with options) to answer.
Why do some dry fruits split open at maturity? | [
"to release toxins",
"to release berries",
"to regenerate",
"to release seeds"
] | D | |
SciQ | SciQ-7365 | bond, atoms, molecules, valence-bond-theory
So the short answer to your first question is: "Molecular orbitals hold atoms together in covalent bonds, and those are a result of electrostatic interactions and the quantum nature of electrons."
Yes, ionic compounds are large collections of ions, and you can't really define "molecules" for them - instead we talk about "formula units" which are the lowest possible whole-number ratio of elements that represent the compound. Groups of covalently bonded atoms are also held together by electrostatic interactions, but since the covalent bonds are so much stronger, a molecular compound can exist "on its own" as a single molecule. Collectively, the forces that hold collections of molecules together are called van der Waals forces if they don't involve ions. In any atom or molecule, there is never a completely uniform charge density on the surface. For some molecules, this is extreme (water is a good example) and we say it is very polar, or that it has a large dipole moment. This is just another way of saying that one part has a negative charge and the other has a positive charge. In water it looks like this (from wikipedia):
In this picture, red means "more electrons" and blue means "less electrons." Water can form hydrogen bonds, which are very strong electrostatic interactions. Some atoms and molecules have an almost uniform charge density on the surface. We call these "non-polar" molecules - noble gases are good examples. However, even noble gases have what is called an induced dipole due to statistically correlated fluctuations in electron density when the atoms are near each other. As a result, even noble gases can be cooled to the point where they become liquid - the very, very weak electrostatic interactions will hold them together at low temperature, when they are not moving very fast. These forces are called London Dispersion Forces - after the guy who first described them. London dispersion forces are important, because they are found in all molecules - polar or not. In fact, this is what makes most plastics solid. Polyethylene, for example, is made of very long chains of essentially non-polar molecules (from wikipedia):
The following is multiple choice question (with options) to answer.
What is an ionic bond in nature? | [
"electrostatic",
"kinetic",
"magnetic",
"radioactive"
] | A | An ionic bond is electrostatic in nature. |
SciQ | SciQ-7366 | waves, atmospheric-science, turbulence
The clouds form if the rising air reaches the lifted condensation level before the updrafts are stopped by an inversion or stable layer. The air is (relatively) clear above the downdrafts. If the convection rolls were perfectly circular, the cloud row spacing would be twice the height of the inversion/stable layer.
Mathematically, there are many wavelength solutions to convection, but the wavelength that dominates is the fastest growing one. In the Boussinesq approximation, which is reasonably valid here, this turns out to have a wavelength of $2\sqrt{2}\sim 3$ times the height of the convecting layer, i.e. slightly flattened. (See, for example, Eq. 21 of Kuettner (1971) "Cloud bands in the earth's atmosphere: Observations and Theory".)
For typical cumulus cloud heights of $\sim 2$ km, we expect typical spacings of about $6$ km.
Wave, lee, or mountain clouds are lines of clouds downwind of an obstacle (such as a mountain range). The lines are parallel to the wind direction. These are buoyancy waves where wind pushes denser air over an obstacle (e.g. a mountain range) and it ends up above less dense air on the other side. This dense air starts to fall but it overshoots into even higher density air at lower altitude, which forces it back up, and the air ends up bouncing up and down until the oscillations die out. If the vertical temperature profile of the air then is known, it is possible to estimate the vertical buoyancy angular frequency
$$N=\sqrt{\frac{g}{\theta}\frac{d\theta}{dz}}$$
The following is multiple choice question (with options) to answer.
Most air masses form over what two types of regions? | [
"arctic and marine",
"polar and tropical",
"marine and tropical",
"polar and arctic"
] | B | Most air masses form over polar or tropical regions. They may form over continents or oceans. Air masses are moist if they form over oceans. They are dry if they form over continents. Air masses that form over oceans are called maritime air masses. Those that form over continents are called continental air masses. Figure below shows air masses that form over or near North America. |
SciQ | SciQ-7367 | entomology
Title: The death of Earthworm In rainy season when children sprinkle salt on earthworm ,it dies.But salt is not dangerous.We use it daily.Then why earthworm dies? It's because on the earth worm skin's special mucous. Acording to this article: Why do earthworms die when salt is sprinkled on them? the mucous makes moist to the worm's skin, which is vital for their survival. Moreover, the worms don't have a respiratory organs, like lungs, gills, etc. This means that Carbon Dioxide and other characterized as "dump" gases can not be exchanged with the Oxygen. But worms breath through their skin, with the help of these special mucous that are developed on its skin. If their skin dries out the result will be death, because the gas exchange will not last without the mucous help. Similarly, the circulatory system won't function, because its main role is to trade gasses with the cells via red blood cells.
What about salinity?
Salinity is a very important factor for the earthworms health, because high salinity destroy their valunable and sensitive skin and kills the mucous that in fact help the worm to "breathe". Low salt concentrations are very beneficial for the worm, because not only their mortarity level is increaced, there are size changes to the worm's body (noticeable bigger size).
Here are and some photos of a worm that its enviroment has low salinity and high salinity:
High salinity:
Low-to-medium salinity
Source: Why do earthworms die when salt is sprinkled on them?.
The following is multiple choice question (with options) to answer.
Earthworms are important deposit feeders that help form and enrich what material? | [
"shale",
"coal",
"wood",
"soil"
] | D | Earthworms are important deposit feeders that help form and enrich soil. |
SciQ | SciQ-7368 | botany
Title: What are embryophytes? And how are they characterized? What does it mean when it's said that plants are embryophytes?
What are the specific characteristics that help determine that? The name derives from their innovative characteristic of nurturing the young embryo sporophyte during the early stages of its multicellular development within the tissues of the parent gametophyte.
source
https://www.revolvy.com/main/index.php?s=Embryophytes&item_type=topic
Similar definitions are in the New World Encyclopedia and Merriam Webster Dictionary.
The following is multiple choice question (with options) to answer.
Growth, morphogenesis, and cell differentiation produce the plant what? | [
"tail",
"body",
"fur",
"fat"
] | B | 35.5 Growth, morphogenesis, and cell differentiation produce the plant body. |
SciQ | SciQ-7369 | zoology
Title: What is right below skin? I was skinning a gopher so my cat can eat it (it was a pest and we didn't want to waste it). I thought its organs would fall out and make a mess, but that didn't happen. There was this sticky, transparent substance that surrounded its insides. What is this casing called? My dad said it was mucus but that isn't specific enough since there is mucus inside the stomach so I don't think they are the same.
I think this casing is found in all multicellular animals but I couldn't be sure. Based on your reference to organs falling out and the overall description, I presume you're thinking of the abdominal cavity primarily, so there you'd be looking at the peritoneum or possibly the serous membranes of other organs (e.g., pleura, pericardium). These are membranous (in the general sense, not as a cell membrane) connective tissues covering the organs found in the abdomen and chest.
Other things you'll find underneath skin would include layers of fat, other connective tissues, muscle.
Here's a labeled image of a mouse dissection from Friedrich, L., Schuster, M., de Celis, M. F. R., Berger, I., Bornstein, S. R., & Steenblock, C. (2021). Isolation and in vitro cultivation of adrenal cells from mice. STAR protocols, 2(4), 100999.:
You might also look for dissections of fetal pigs or cats, which are commonly used in laboratory demonstrations for students (more often cats longer ago, more often fetal pigs these days).
The following is multiple choice question (with options) to answer.
What is a fold of the outer skin lining the shell called? | [
"stack",
"cortex",
"mantle",
"marble"
] | C | A mantle , or fold of the outer skin lining the shell. The mantle often releases calcium carbonate, which creates an external shell, just like the ones you find on the beach. The shell is made of chitin , a tough, semitransparent substance. |
SciQ | SciQ-7370 | tissue
Title: What are the main differences between lab-grown tissues and natural tissues from living animals? What are the main differences between lab-grown tissues and natural tissues from living animals?
Using a biologist's classic "structure (anatomy) and function (physiology)" idea, I thought about the followings:
Structure:
It might be difficult to recreate the composition of different tissues / cells in living things precisely with artificial methods. This may lead to bad results when the tissue is used for tests of medicines and cosmetics.
Function:
Cells might not function and produce as expected (or is harder to make them function) in artificial compositions, as cells need strictly regulated environments to function correctly.
The following is multiple choice question (with options) to answer.
What sciences are the study of living organisms? | [
"physical sciences",
"life sciences",
"earth sciences",
"social sciences"
] | B | The life sciences are the study of living organisms. They deal with every aspect of living organisms, from the biology of cells , to the biology of individual organisms, to how these organisms interact with other organisms and their environment. |
SciQ | SciQ-7371 | zoology, ecology, species-distribution, migration
Title: How do animals end up in remote areas? I was thinking specifically about random marshy water holes on farmers fields. It seems that you can visit just about any one of these and you will find frogs if you look hard enough.
They usually don't seem to be connected to each other. If it were any other land animal I would figure they walk from one spot to another, but in the case of frogs, I don't imagine their range is very vast. But often these marshy spots can be separated by fairly large distances to a frog.
So this brings me to my question: how do each of these spots end up with frogs in them? I don't imagine a frog is going to go hopping over a hill to get to a marsh on the other side, is it? This question pertains to organism dispersal, which is a very active field of study with relation to it's impact on conservation efforts. Much of what I will say below has been covered in this wiki.
Definition: From the Wiki
Technically, dispersal is defined as any movement that has the
potential to lead to gene flow.
It can be broadly classified into two categories:
Density dependent dispersal
Density independent dispersal
The question of frogs and fishes both refer to Density independent dispersal, while an example of density independent dispersal can be the competition for habitat space between big cats and humans (this is a WWF pdf)
From the wiki:
Density-independent dispersal
Organisms have evolved adaptations for dispersal that take advantage
of various forms of kinetic energy occurring naturally in the
environment. This is referred to as density independent or passive
dispersal and operates on many groups of organisms (some
invertebrates, fish, insects and sessile organisms such as plants)
that depend on animal vectors, wind, gravity or current for dispersal.
Density-dependent dispersal
Density dependent or active dispersal for many animals largely depends
on factors such as local population size, resource competition,
habitat quality, and habitat size.
Currently, some studies suggest the same.
This study in particular studied the movement and habitat occupancy patterns within ephemeral and permanent water bodies in response to flooding. They found that during flooding these frogs moved out to flooded ephemeral water bodies and later on moved back again to the permanent ones.
Other suggested readings for those highly interested in the subject may include this (a phd thesis) and this (a project report)
The following is multiple choice question (with options) to answer.
Frogs are amphibians that live part of the time in fresh water and rest of the time where? | [
"in stagnant water",
"in salt water",
"underground",
"on land"
] | D | Amphibians are vertebrates that live part of the time in fresh water and part of the time on land. They were the first vertebrates to evolve four legs and colonize the land. They most likely evolved from lobe-finned fish. Modern amphibians include frogs, toads, salamanders, newts, and caecilians. They are ectotherms, so they have little control over their body temperature. This allows them to be active in warm weather, but they become sluggish when the temperature cools. |
SciQ | SciQ-7372 | homework-and-exercises, newtonian-mechanics, classical-mechanics
At the request of @Alex in the comments, here's the equation of motion.
Note that $\alpha$ may not be constant here, due to the peculiar geometry of the problem. I've assumed it to be constant for the sake of simplicity.
$$F-F_f=ma_x$$
where $F_f$ is the friction force, needed for the no slipping equirement.
$$F=mg\sin\alpha$$
$$F_f=\mu N=\mu mg\cos\alpha$$
with $\mu$ the minimum friction coefficient required for rolling without slipping.
$$a_x=g\sin\alpha-\mu g\cos\alpha\tag{1}$$
$\mu$ now needs to be determined.
Torque causes rotation:
$$\tau(x)=R(x)F_f=\dot{\omega}I$$
Note that due to the geometry of the problem, $R(x)$ is a function of $x$ (not determined here).
Rotation without slipping means:
$$v_x=R(x)\omega$$
$$a_x=\frac{\partial \omega}{\partial t}=R(x)\dot{\omega}$$
$$\dot{\omega}=\frac{a_x}{R(x)}=\frac{\mu mg\cos\alpha R(x)}{I}$$
$$a_x=\frac{\mu mg\cos\alpha R^2(x)}{I}\tag{2}$$
From $(1)$ and $(2)$, $\mu$ could then be determined.
The following is multiple choice question (with options) to answer.
Name the missing type of friction: static, rolling, fluid _____? | [
"sliding",
"falling",
"turning",
"dragging"
] | A | Friction is the force that opposes motion between any surfaces that are in contact. There are four types of friction: static, sliding, rolling, and fluid friction. |
SciQ | SciQ-7373 | 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 is the study of how living organisms interact with each other and with their environment? | [
"zoology",
"botany",
"genetics",
"ecology"
] | D | Recall that ecology is the study of how living organisms interact with each other and with their environment. But how do organisms interact with each other? Organisms interact with each other through various mechanisms, one of which is competition. Competition occurs when organisms strive for limited resources. Competition can be for food, water, light, or space. This interaction can be between organisms of the same species (intraspecific) or between organisms of different species (interspecific). |
SciQ | SciQ-7374 | electrons, metal, electronic-configuration
Title: Can a metal be forced to form an anion theoretically? I know that metals have the capability to lose electrons and form cations, but is it also theoretically possible to supply an electron to a metal so that it forms an anion?
If so, has it ever been done?
I referred this question (Can two metals combine to form a compound?) but could not get a satisfactory solution from that. Absolutely! You will find these mostly in electride systems and off these, mostly in alkali metals.
Here is an example research paper:
"Superakali-Alkalide Interactions and Ion Pairing in Low-Polarity Solvents, J. Am. Chem. Soc., 2021, 143(10), 3934–3943 (https://pubs.acs.org/doi/10.1021/jacs.1c00115)
Remember, metals have a positive charged when ionized because it is energetically more favorable to lose electrons than to gain them, this being of course an oversimplified version of electron orbitals and shells. If you have a situation in which this is reverse or not possible, you will get a negative metal ion
The following is multiple choice question (with options) to answer.
What are electrons lost during the formation of ions called? | [
"isotopes",
"cations",
"oxides",
"catalysts"
] | B | Some elements lose one or more electrons in forming ions. These ions are known as “ cations ” because they are positively charged and migrate toward the negative electrode ( cathode ) in an electrical field. Looking at the periodic table below, we know that the group 1 elements are all characterized by having one s electron in the outer orbit and group 2 elements have two s electrons in the outer orbit. These electrons are loosely attached to the atom and can easily be removed, leaving more protons in the atom that there are electrons, so the resulting ion has a positive charge. Cations can also be formed from electron loss to many of the transition elements. |
SciQ | SciQ-7375 | Moreover, if you want to know about the logic in general terms this article could be useful.
Logic, originally meaning "the word" or "what is spoken", but coming to mean "thought" or "reason", is a subject concerned with the most general laws of truth, and is now generally held to consist of the systematic study of the form of valid inference. A valid inference is one where there is a specific relation of logical support between the assumptions of the inference and its conclusion.
• Hmm, I'm not sure if this is very helpful here. Would you say that David's post makes yours 'superseded'? If not, why? Try to expand on that. – Discrete lizard Mar 25 '18 at 14:03
• @OmG : Can you recommend a list of materials to learn from ? – Sheldon Kripke Mar 31 '18 at 3:54
The following is multiple choice question (with options) to answer.
Making a specific statement based on a general principle is the definition of what type of reasoning? | [
"inductive",
"deductive",
"inference",
"transitive"
] | B | Deductive reasoning means making a specific statement based on a general principle. |
SciQ | SciQ-7376 | 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.
The earth's magnetic poles have done what repeatedly in the past? | [
"switched places",
"rotated",
"demagnetized",
"stayed the same"
] | A | Earth’s magnetic poles have switched places repeatedly in the past. As you can see in the Figure below , each time the switch occurred, Earth’s magnetic field was reversed. The magnetic field is the region around a magnet over which it exerts magnetic force. We think of today’s magnetic field direction as “normal,” but that’s only because it’s what we’re used to. You can watch a simulation of a magnetic field reversal at this URL: http://www. pbs. org/wgbh/nova/earth/when-our-magnetic-field-flips. html. |
SciQ | SciQ-7377 | cell-biology, mitochondria, mitosis
Title: Are cells guaranteed to get at least one mitochondrion when they divide? If mitochondria exist at random within a cell, isn't there a possibility that cell division will result in a daughter cell with no mitochondria? If not, what is the process for guaranteeing at least one is present in each daughter cell? If so, what happens to that cell?
Isn't there a possibility that cell division will result in a daughter
cell with no mitochondria?
Yes, there is always the possibility. However, there must be a strong negative selection pressure against eukaryotic life that cannot achieve the proper partitioning of mitochondria, so you can imagine that there are mechanisms in place to prevent this case.
Mitochondria are both passively and actively partitioned to daughter cells. This is understood to occur through the cytoskeleton and with the control of mitochondrial fusion and fission at key stages of the cell cycle, prior to mitosis and cytokinesis!
Here is a great review from several years ago that addresses your question well.
The following is multiple choice question (with options) to answer.
What do we call the orderly sequence of events in the life of a cell from the division of a single parent cell to produce two new daughter cells, to the subsequent division of those daughter cells? | [
"circadian cycle",
"cell replication",
"cell cycle",
"cell death"
] | C | 6.1 | The Genome By the end of this section, you will be able to: • Describe the prokaryotic and eukaryotic genome • Distinguish between chromosomes, genes, and traits The continuity of life from one cell to another has its foundation in the reproduction of cells by way of the cell cycle. The cell cycle is an orderly sequence of events in the life of a cell from the division of a single parent cell to produce two new daughter cells, to the subsequent division of those daughter cells. The mechanisms involved in the cell cycle are highly conserved across eukaryotes. Organisms as diverse as protists, plants, and animals employ similar steps. |
SciQ | SciQ-7378 | resources, soil
Title: Is soil a renewable resource? My geology textbook tells me that soil is not renewable, and I agree with this, but there was some question in my class as to whether this is true.
Some soils take more than a human lifetime to regenerate. However, in crop production, it seems as if soil can be regenerated with additives.
In the scientific community of soil scientists, is soil considered a renewable resource by most of those scientists? Is there strong evidence to support this? Soil is an interesting case because although it is non-renewable (at any useful rate) as a 'bulk material' once removed from the ground, the nutrient content of soil can be renewed with fertilizers.
What a soil-scientist would understand as 'soil' is ultimately produced from the physical and chemical breakdown of solid bedrock at the base of the soil horizon. The rate at which this happens for natural soil production can vary substantially depending on the climatic conditions and other factors, but typically could range from 0.1 to 2.0 mm/yr.
In many intensively farmed regions, (top)soil is being removed by erosion much faster than it is being replaced by natural process. Removal of vegetation cover is enough to expose bare soil to rainsplash erosion at rates much greater than it is renewed. Once soil is bare, it becomes much more susceptible to erosion.
I think the additives you are referring to replenish the nutrient content of the soil, and not the the bulk material that would be produced by bedrock decomposition. With careful management, the fertility of existing soil can be maintained. But if the soil is allowed to be washed off or erode, for all practical purposes, the rate of replenishment is not fast enough for it to be classed as renewable in that sense.
This site has links to more aspects surrounding this issue.
The following is multiple choice question (with options) to answer.
What are natural resources which can be replaced in a relatively short period called? | [
"renewable resources",
"solvent resources",
"replaceable resources",
"materials resources"
] | A | Renewable resources are natural resources that can be replaced in a relatively short period of time or are virtually limitless in supply. Renewable energy resources include sunlight, moving water, wind, biomass, and geothermal energy. Each of these energy resources is described in Table below . Resources such as sunlight and wind are limitless in supply, so they will never run out. Besides their availability, renewable energy resources also have the advantage of producing little if any pollution and not contributing to global warming. The technology needed to gather energy from renewable resources is currently expensive to install, but most of the resources themselves are free for the taking. |
SciQ | SciQ-7379 | redox, biochemistry, energy, electrons
Title: What are high-energy electrons? I read that (in cellular respiration) the transported electrons in NADH have a higher energy than those in FADH2.
I can't find a (simple or otherwise) explanation of what a "high-energy" electron is.
I came across a post on Reddit which asks the same question:
I am not a chemist but I am trying to understand what my biochemistry book
means by "high energy electrons" that are obtained from glycolysis and
the citric acid cycle. I am assuming that this "high energy" is not a
property of the electrons themselves, but it is not clear to me in
what way they are "high energy". Do they mean that when these
electrons are transferred to the electron carriers they are part of
molecular structures in which they sit in high energy positions?
(There were no satisfactory answers to the question).
Could anyone come up with a definition understandable by this non-chemist (i.e. me)?
transported electrons in $\ce{NADH}$ have a higher energy than those in $\ce{FADH2}.$
This is jargon describing the redox potential of the electron carrier $\ce{NADH}/\ce{NAD+}$ vs the electron carrier $\ce{FADH2}/\ce{FAD}.$ So if you compare the two reduction half reactions
$$
\begin{align}
\ce{NAD+ + H+ + 2e- &-> NADH} &\quad E^{\circ '}_\mathrm{red} &= \pu{-0.320 V}\tag{1}\\
\ce{FAD + 2H+ + 2e- &-> FADH2} &\quad E^{\circ '}_\mathrm{red} &= \pu{0.031 V}\tag{2}
\end{align}
$$
$\ce{NADH}$ is the stronger reducing agent.
Could anyone come up with a definition understandable by this non-chemist (i.e. me)?
The following is multiple choice question (with options) to answer.
The biological electron transport chain provides for an orderly, stepwise transfer of electrons. both nadh (reduced nicotinamide adenine dinucleotide) and fadh2 (reduced flavin adenine dinucleotide) are energy rich molecules that liberate a large amount of energy during what? | [
"extrapolation",
"conduction",
"evaporation",
"oxidation"
] | D | The biological electron transport chain provides for an orderly, stepwise transfer of electrons. Both NADH (reduced nicotinamide adenine dinucleotide) and FADH2 (reduced flavin adenine dinucleotide) are energyrich molecules that liberate a large amount of energy during oxidation. Free energy released during the transfer of electrons from either of these molecules to oxygen drives the synthesis of ATP (adenosine triphosphate) formed during respiratory metabolism. The reactions are as follows:. |
SciQ | SciQ-7380 | botany, plant-physiology
Title: Can any plant regenerate missing tissue? I have not yet found a plant that, when an insect eats a hole in one of its leaves, it can regenerate the lost tissue. Many plants will grow a new stem if the old one is cut, but it is not a perfect regeneration, and has no likeness in form to the previous stem. Are there any plants that can, even to a degree, regenerate missing tissue? In general, plant cells only undergo differentiation at special regions in the plant known as meristems. Two of the primary types of meristem are the root apical meristem (at the tips of roots) and the shoot apical meristem (at shoot tips)^. Within the shoot apical meristem the plant cells divide and begin to differentiate into different cell types (such as different cells of the leaf, or vascular cells). Later growth (of, say, a leaf) is largely a result of cell expansion (although cell division does still occur, but drops off as the leaf expands). Therefore, if you punch a hole in a leaf, it probably won't be filled in because the cells in that leaf have finished growing and dividing.
However, as a shoot grows, more meristems are created. These are found in the axillary buds, just above where the leaf meets the stem. The meristems in the axillary buds can grow to form branches. Different plants obviously make different numbers of branches, but there is a common control mechanism known as apical dominance, where the meristem at the tip of the shoot suppresses the growth of the lower axillary buds. This is why a shoot with no branches can be made to grow branches by cutting off the tip (gardeners often do this to make "leggy" plants more bushy).
All of that was a long explanation to say, no, a plant doesn't normally^^ regenerate in the sense of filling in cells that have gone missing. However, if you cut off a shoot, the next remaining bud might begin to grow and, in a sense, replace the part that was lost. In that case, an existing bud is recruited to form a new branch and replace lost functionality, but I wouldn't say that qualifies as regenerating missing tissue.
^There are other types of meristem as well.
The following is multiple choice question (with options) to answer.
The cells within meristems divide relatively frequently, generating additional what? | [
"chlorophyll",
"proteins",
"cells",
"photosynthesis"
] | C | |
SciQ | SciQ-7381 | energy, energy-conservation, biophysics
Title: How efficient is the human body? This question sort of comes to mind when hearing how efficient an internal combustion engine is turning chemical energy in mechanical energy (something like 20-40%) with lots of excess heat. As an analog, how efficient is (or potentially) the human body at turning food into energy? Please bare with me, I realise there LOTS of different variables (how much the person weighs vs mass, metabolism, diet, etc). But I would imagine that there shouldn't be much margin of error given that most people maintain the same constant temperature (98 F +/- 1 degree). The MET (Metabolic Equivalent Task) readout on your gym equipment is your body doing 1Kcal/kg/h = 4184 J/kg/h and can be reasonably accurately measured by how much oxygen a test victim uses.
Sitting still is roughly 1 met and cycling at 100 Watts is around 5.5 Mets.
So taking a man of 75kg, cycling at 100Watts (100J/s) he is having to do 5.5 * 4184 * 75 / 3600s = 480Watts so an efficency of 20%
Remember though that the person is spending 80-100Watts just staying alive doing nothing - unlike your car. There is an interesting experimental fit to how much energy you need to just stay alive, calculated about 100 years ago, the Harris-Benedict equation
The following is multiple choice question (with options) to answer.
Another unit of energy, used widely in the health professions and everyday life, is _______? | [
"body index",
"carbs",
"biomass ( cal )",
"calorie ( cal )"
] | D | example, if you hold an ice cube in your hand, the ice cube slowly melts as energy in the form of heat is transferred from your hand to the ice. As your hand loses energy, it starts to feel cold. Because of their interrelationships, energy, work, and heat have the same units. The SI unit of energy, work, and heat is the joule (J). A joule is a tiny amount of energy. For example, it takes about 4 J to warm 1 mL of H2O by 1°C. Many processes occur with energy changes in thousands of joules, so the kilojoule (kJ) is also common. Another unit of energy, used widely in the health professions and everyday life, is the calorie (cal). The calorie was initially defined as the amount of energy needed to warm 1 g of H2O by 1°C, but in modern times, the calorie is related directly to the joule, as follows: 1 cal = 4.184 J We can use this relationship to convert quantities of energy, work, or heat from one unit to another. The calorie is used in nutrition to express the energy content of foods. However, because a calorie is a rather small quantity, nutritional energies are usually expressed in kilocalories (kcal), also called Calories (capitalized; Cal). For example, a candy bar may provide 120 Cal (nutritional calories) of energy, which is equal to 120,000 cal. Proteins and carbohydrates supply 4 kcal/g, while fat supplies 9 kcal/g. |
SciQ | SciQ-7382 | c
Title: Match blood types in C I have written a solution to the blood-type matching problem, as described at https://projectlovelace.net/problems/blood-types/. The problem is to determine whether a given recipient (in this case, argv[1]) will find a match for a blood transfusion in an array of available donors (argv + 2).
Input blood type: B+
Input list of available blood types: A- B+ AB+ O+ B+ B-
Output: match
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <err.h>
typedef struct {
enum { O, A, B, AB } abo;
enum { P, M } rh;
} Blood;
const int abo[4][4] = {
{ O, O, O, O }, // O
{ O, A, O, A }, // A // *
{ O, B, O, B }, // B // *
{ O, A, B, AB }, // AB
};
const int rh[2][2] = {
{ P, M }, // P
{ M, M }, // M // *
};
Blood
parse(char *s){
char rh0 = s[strlen(s)-1];
char *abo0 = strdup(s);
abo0[strlen(s)-1] = '\0';
Blood b = {
!strncmp(abo0, "O", 1) ? O
: !strncmp(abo0, "A", 1) ? A
: !strncmp(abo0, "B", 1) ? B
: !strncmp(abo0, "AB", 2) ? AB
: -1,
rh0 == '+' ? P
: rh0 == '-' ? M
: -1,
};
return b;
}
The following is multiple choice question (with options) to answer.
What are the specfic types of proteins that determine your blood type called? | [
"Plasma",
"antigens",
"antibodies",
"Globulins"
] | B | Red blood cells carry proteins called antigens on their surface. People may vary in the exact antigens their red blood cells carry. The specific proteins are controlled by the genes they inherit from their parents. The particular antigens you inherit determine your blood type. |
SciQ | SciQ-7383 | geology, mineralogy, minerals, weathering
To me, supergene has a specific meaning, it may be part of the weathering process in some locations, but weathering involves the breaking down of rocks due to: reactions with atmospheric gasses, water (usually rain), changes brought on by plants, bacteria wind and temperature.
My suggestion to use the term weathering or weathered.
The following is multiple choice question (with options) to answer.
Which layer of soil experiences the most weathering? | [
"humus",
"bedrock",
"top layer",
"subsoil"
] | C | Soil develops over time and forms soil horizons. Soil horizons are different layers of soil with depth. The most weathering occurs in the top layer. This layer is most exposed to weather! It is where fresh water comes into contact with the soil. Each layer lower is weathered just a little bit less than the layer above. As water moves down through the layers, it is able to do less work to change the soil. |
SciQ | SciQ-7384 | 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.
Osteoporosis, osteoarthritis, fractures, and sprains are problems affecting what system? | [
"skeletal system",
"nervous system",
"digestive system",
"tissues system"
] | A | Possible problems of the skeletal system include osteoporosis, osteoarthritis, fractures, and sprains. |
SciQ | SciQ-7385 | graphs, neural-networks, randomness, network-topology
Title: Which neural network topology is the most efficient to generate randomly shaped letters? I have created some unique shapes, so-called "letters" for a custom alphabet, all of which can fit into 9x9 pixels. Instead of drawing countless more, I try to combine two solutions I saw in a relevant part of Reddit, and decided to let a neural network create some additional examples.
Desconstructing the problem: letters are formed in a graph of 25 nodes (always ordered into a 5x5 square) by spontaneously connecting only the adjacent nodes - no diagonal or non-adjacent edges are present.
For a neural network input, I drew these runes into 9x9 blocks, where each row has 5 "pixels" for each nodes, and 4 more as a place for indicating connection.
Below is the current letter set, with an example of an empty graph and the only example generated by my network in the last line.
The following is multiple choice question (with options) to answer.
What are typically arranged into complex tubular networks with extensive surface areas? | [
"Golgi apparatus",
"alveoli",
"hair follicles",
"transport epithelia"
] | D | |
SciQ | SciQ-7386 | 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.
What is the simplest unit of structure and function of all living organisms called? | [
"molecule",
"atom",
"partical",
"cell"
] | D | A cell is the simplest unit of structure and function of all living organisms. From the smallest bacteria to the largest whale, all life is made of at least one cell. |
SciQ | SciQ-7387 | 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.
Activities that can reduce the effects of what condition include exercises to keep the blood and lymph flowing through affected areas? | [
"anemia",
"asthma",
"edema",
"inflammation"
] | C | Medications that can result in edema include vasodilators, calcium channel blockers used to treat hypertension, nonsteroidal anti-inflammatory drugs, estrogen therapies, and some diabetes medications. Underlying medical conditions that can contribute to edema include congestive heart failure, kidney damage and kidney disease, disorders that affect the veins of the legs, and cirrhosis and other liver disorders. Therapy for edema usually focuses on elimination of the cause. Activities that can reduce the effects of the condition include appropriate exercises to keep the blood and lymph flowing through the affected areas. Other therapies include elevation of the affected part to assist drainage, massage and compression of the areas to move the fluid out of the tissues, and decreased salt intake to decrease sodium and water retention. |
SciQ | SciQ-7388 | inorganic-chemistry, alloy
Title: If alloys are homogeneous mixtures, why can't we separate their components? An alloy is a material composed of two or more metals or a metal and a nonmetal. And, they are usually formed by heating the elements to their melting points, and then cooling them, so that the components mix. Now, why doesn't this works backwards i.e. if we heat the alloy again to melting point of their constituents, and they should separate? Once the alloy has been formed the atoms from the different metals will have shared there electrons with each other and come to an equilibrium. In this state the metal atoms have formed a complex structure which has a different reactivity or properties than each individual metal did in its original form .
The following is multiple choice question (with options) to answer.
An alloy is a mixture of metals that has bulk metallic properties different from those of its what? | [
"constituent elements",
"nuclear elements",
"mineral elements",
"system elements"
] | A | atoms held together by covalent bonds; they tend to be very hard and have high melting points. Metallic solids have unusual properties: in addition to having high thermal and electrical conductivity and being malleable and ductile, they exhibit luster, a shiny surface that reflects light. An alloy is a mixture of metals that has bulk metallic properties different from those of its constituent elements. Alloys can be formed by substituting one metal atom for another of similar size in the lattice (substitutional alloys), by inserting smaller atoms into holes in the metal lattice (interstitial alloys), or by a combination of both. Although the elemental composition of most alloys can vary over wide ranges, certain metals combine in only fixed proportions to form intermetallic compounds with unique properties. |
SciQ | SciQ-7389 | human-physiology, digestion, stomach
The stomach accomplishes much of its function by mechanically breaking down the swallowed food particles and mixing them with acid and enzymes into a sort of slurry. To do this, there are three major layers of muscle surround the stomach - from the outside, the longitudinal layer, the circular layer, and the oblique layer. The stomach also has two holes in it - the gastroesophageal opening, coming from the esophagus with the swallowed food/saliva mix, and the pylorus, where the food/acid/enzyme slurry exits into the duodenum, which is the beginning of the small intestine.
Due to the three layers of (rather strong) muscle, the stomach doesn't have a lot of expansion capability once it is filled completely to capacity. Fortunately, this almost never occurs (despite how we may feel after a large meal) because material is always leaving the stomach on its way to enzymatic digestion in the intestines. Additionally, once the stomach is filled to a certain extent, hormones such as leptin are secreted that give you the feeling of being sated, or full, triggering the brain to make you stop eating.
Of course, as we can see with the current epidemic of obesity around the world, the stomach can change its size over time. However, this is a rather slow process (weeks to months to years) of adapting to continuously consuming large meals.
But what would happen if you completely ignored these internal warnings, or were being force-fed, or whatever? Instead of rupturing (the biological equivalent of "exploding"), food would most likely be expelled either into the small intestine or back into the esophagus and back up the way it came down, i.e. causing vomiting.
The following is multiple choice question (with options) to answer.
There are two types of digestion, mechanical and what else? | [
"mineral",
"thermal",
"chemical",
"radiation"
] | C | Digestion consists of mechanical and chemical digestion. |
SciQ | SciQ-7390 | thermodynamics, energy, terminology
You are absolutely correct. Heat is not a form of energy. It is a mechanism by which energy is transferred from one substance, object, etc., to another due solely to temperature difference.
When I was learning about thermodynamics I found a particular description that, at least for me, help differentiate between the energy of something and the transfer of energy (by work or heat) from one thing to another. In this case the transfer of energy by heat. I'd like to share it with you in case it might be helpful. For simplicity, the description is for heat conduction.
Consider two solid objects, one having a higher temperature than the other. Which means the molecules of the higher temperature object 1 have a higher average translational kinetic energy than the molecules of the lower temperature object 2.
The objects are placed in contact with each other. At the interface between the objects the molecules of the higher temperature object collide with the molecules of the lower temperature object. On average, this results in the transfer of kinetic energy from the molecules of the higher temperature object to molecules of the lower temperature object causing the temperature of the higher temperature object to decrease, and the temperature of the lower temperature object to increase.
This transfer of kinetic energy from the molecules of the higher temperature object to the molecules of the lower temperature object is what we mean by heat. But the increase in the average kinetic energy of the molecules of the lower temperature object and decrease in the average kinetic energy of the molecules of the higher temperature object is what we mean by a change in the internal (kinetic) energy of the two objects. Thus the difference between the transfer of energy and the energy itself.
Hope this helps.
The following is multiple choice question (with options) to answer.
What is the rate at which energy is being transferred called? | [
"force",
"electric",
"pressure",
"power"
] | D | Power is the rate at which energy is being transferred. Power tells you how many Joules per second of energy is being used to drive something. Thus power is simply the change in energy divided by the time. Since work is by definition the transfer of energy (in or out of a system), power is also equal to the work divided by the time. Efficiency tells you how efficient something is and gives a number between 0 and 1. If the efficiency is equal to 1, then the machine is perfectly efficient (that is all the power used to drive it goes to the out put of the machine with no energy losses). If the efficiency is zero, then all of the input power is lost in the machine and the machine can not output any energy. |
SciQ | SciQ-7391 | proteins, food, digestive-system, amino-acids, digestion
Title: How are proteins reused in the body? Part of what we eat are proteins,
and our body is in part build of proteins.
Are the proteins of the body build based on proteins in food at all?
Are proteins in food directly reused in the body,
or are proteins first disassembled?
How far are they disassembled, randomly in various pieces, or systematically to keep what can optimally be used to build new proteins, while nothing is wasted for energy?
(The question Can proteins/peptides pass through the intestine? and it's answers are related, and provide some context and relevant parts, but is not a duplicate.) Short answer: Indeed the proteins in our body are based on amino acids from external food sources. BUT, proteins up-taken from food are ALWAYS disassembled first into amino acids, through specialized enzymes, proteases, (for instance Pepsin in the stomach's gastric juices and Tripsin in the pancreatic juices), during digestion, in the alimentary canal, (gut). This enables the body's liver to build the proteins most needed by the organism itself, through the processes of transamination, that allows conversion betwixt amino acids, and deamination, that removes N2 from the amino acid, (let's say the "amino" part is removed, and then expelled as urea), to excrete amino acids in excess. In addition this breaking down of external proteins is necessary, since they can act as labels for pathogens, and external organisms in general, and thus would soon be destroyed by the immune system if reused straight away.
The following is multiple choice question (with options) to answer.
Where does the process of assembling amino acids into a protein take place? | [
"in chromosomes",
"in the ribosome",
"in the nucleus",
"in the chitin"
] | B | The process of assembling amino acids into a protein takes place in the ribosome. This structure consists of two subunits, each of which is composed of both proteins and ribosomal RNA (rRNA). The two subunits clamp together on the mRNA and catalyze the formation of the amide linkages in the growing protein. When protein synthesis is complete, the two subunits dissociate and release the completed protein chain. |
SciQ | SciQ-7392 | acid-base, equilibrium, aqueous-solution, ph, stoichiometry
$$
Finally, mass $m$ of sodium acetate can be found from its molar mass $M$ and volume of the solution $V$:
$$
\begin{align}
m &= cVM \\
&= \frac{VMK_\mathrm{a}K_\mathrm{w}}{10^{-2\mathrm{pH}}} \\
&= \frac{(\pu{2.50 L})(\pu{82.03 g mol-1})(\pu{1.75E-5})(10^{-14})}{10^{-2\times 9}~\pu{mol-1 L}} = \pu{35.9 g}\tag{5}
\end{align}
$$
The following is multiple choice question (with options) to answer.
Where can you find sodium acetate? | [
"table salt",
"a heat pack",
"a cold pack",
"baking soda"
] | B | In the picture above, a thermal pack is applied to the back. Small packs can be used either for heating or cooling, depending on the material used. A heat pack contains a supersaturated solution of material such as sodium acetate. The solution is clear until a small metal trigger is activated. The sodium acetate then crystallizes out of solution and generates heat in the process. |
SciQ | SciQ-7393 | physical-chemistry, equilibrium, aqueous-solution, solubility, ionic-compounds
Title: Seeing solubility in various cases
Match the following:
$\begin{array}{|c|c|c|c|} \hline &\textrm{Column-I}&&\textrm{Column-II} \\\hline \textrm{(A)}&\ce{AgBr}&\mathrm{(p)}&\mathrm{(Solubility~in~water~is~more~than~expectation)} \\ \hline \textrm{(B)}&\ce{AgCN}&\mathrm{(q)}&\mathrm{(Solubility~in~acidic~solution~is more~than~in~pure~water~\\(consider~no~common~ion~effect~from~anion~of~acid)}\\ \hline \textrm{(C)}&\ce{Fe(OH)3}&\mathrm{(r)}&\mathrm{(Solubility~in~strongly~basic~solution~is~more~than~in ~pure~water)}\\ \hline \textrm{(D)}&\ce{Zn(OH)2}&\mathrm{(s)}&\mathrm{(Solubility~decreases~in~presence~of~common~anion)}\\ \hline \end{array}$
The following is multiple choice question (with options) to answer.
For a given amount of solute, do smaller particles have a greater or lesser surface area? | [
"greater",
"equal",
"lesser",
"neither"
] | A | A third factor that affects the rate of dissolving is the size of solute particles. For a given amount of solute, smaller particles have greater surface area. With greater surface area, there can be more contact between particles of solute and solvent. For example, if you put granulated sugar in a glass of iced tea, it will dissolve more quickly than the same amount of sugar in a cube (see Figure below ). That’s because all those tiny particles of granulated sugar have greater total surface area than a single sugar cube. |
SciQ | SciQ-7394 | crystal-structure, density-functional-theory, crystallography
Title: How can I find the smaller symmetric structure from big crystal unit cell? I have Pyrope (Mg3Al2(SiO4)3) crystal structure, downloaded from materialsproject:
https://materialsproject.org/materials/mp-6073/#
It appeared as triclinic cell, but if you download CIF file and open it from softwares like Avogadro or VESTA, it appeared as a orthogonal simple cubic (a=b=c, alpha = beta = gamma = 90 degree). I also checked that this geometry is the same with what I downloaded from American Mineralogy Material Database.
Now, I wish to run DFT or quantum calculations for them. So, I excluded atoms in periodic boundary, unit cell contains total 160 atoms. I'm afraid this might be too big, might takes too long time to calculate via DFT or any other quantum simulations. All I need to do is just geometry optimizations, but still, 160 atoms seems too big.
Using VESTA or Avogadro or any other software, is this possible to find the symmetric structure inside this or other "big" unit cell, and make a smaller / simpler version of unit cell for faster calculation?
Or, can I manually cut this unit cell in 1/4 size, 40 atom system with 1/2 size for x, y, and z direction, and run the minimization? It seems that the Pyrope unit cell have some sort of repeating structure inside the big unit cell. But I'm not sure if it is "safe" to find symmetry and divide the unit cell manually.
Thank you No, the unit cell is the smallest translational repeating unit, and any truncation of that would mean that you're calculating a different solid which may or may not exist.
160 atoms is a decent sized unit cell, but is still routinely doable with the right resources. (The materials project page you link to is in fact an automated DFT geometry optimization of that solid, so you could use that)
If you still want to do the calculation yourself then you have to use the whole cell; however, if the unit cell has some additional symmetry (e.g. center of inversion), then a good DFT program will take advantage of that to speed up the calculation.
The following is multiple choice question (with options) to answer.
What is the functional unit of compact bone? | [
"the auteron",
"the boron",
"the osteon",
"the canton"
] | C | Bone matrix provides bones with their basic structure. Notice the spongy bone in the middle, and the compact bone towards the outer region. The osteon is the functional unit of compact bone. |
SciQ | SciQ-7395 | biochemistry, physiology, endocrinology
Title: What is the physiological difference between cortisone and cortisol? There is only hydrogen bond different.
Cortisol is synthesized by our body, while cortisone is given to the patient.
Why you cannot give cortisol directly to the patient?
I think the reason is metabolism that cortisol will break (probably in liver) and not be useful.
Or expansive to produce.
Cortisone however can be given.
What is the physiological difference between cortisone and cortisol? Cortisol is directly given to the patient - it is then called Hydrocortisone. I don't know why this is done but probably to avoid confusion because both names are too similar.
The difference between both forms is one hydrogen atom at the C11 position of the molecule in Cortisol (or Hydrocortison) (image from here):
Otherwise is Cortisol (or Hydrocortisone) the active version, while Cortisone isn't very active in the human body.
Both forms can enzymatically turned into the other form (from active to inactive and vice versa). Since Cortisone needs to be activated in the liver, it can only be used for oral uptake. Most of the uses which are colloquially called Cortisone in fact contain Hydrocortisone.
The following is multiple choice question (with options) to answer.
Mineralocorticoids are hormones synthesized by the adrenal cortex that affect what balance, by regulating sodium and water levels? | [
"equilibrium",
"blood pressure",
"homeostasis",
"osmotic"
] | D | Mineralocorticoids Mineralocorticoids are hormones synthesized by the adrenal cortex that affect osmotic balance. Aldosterone is a mineralocorticoid that regulates sodium levels in the blood. Almost all of the sodium in the blood is reclaimed by the renal tubules under the influence of aldosterone. Because sodium is always reabsorbed by active transport and water follows sodium to maintain osmotic balance, aldosterone manages not only sodium levels but also the water levels in body fluids. In contrast, the aldosterone also stimulates potassium secretion concurrently with sodium reabsorption. In contrast, absence of aldosterone means that no sodium gets reabsorbed in the renal tubules and all of it gets excreted in the urine. In addition, the daily dietary potassium load is not secreted and the retention of K+ can cause a dangerous increase in plasma K+ concentration. Patients who have Addison's disease have a failing adrenal cortex and cannot produce aldosterone. They lose sodium in their urine constantly, and if the supply is not replenished, the consequences can be fatal. |
SciQ | SciQ-7396 | breathing
Title: Why does the pulmonary artery have higher glucose concentration than the pulmonary vein? If the pulmonary artery have higher glucose concentration than the pulmonary vein, does it mean glucose will be consumed during gas exchange?
That confused me because gas exchange is something like diffusion and shouldn't consume any glucose Gas exchange doesn't but the cells of the tissue it occurs in do consume glucose, even the cells in the walls of the artery will consume some. The cells in the lungs still need to be fed and only one of those two vessels has flow going into the tissue so it is the one that has to carry that glucose into the tissue.
The following is multiple choice question (with options) to answer.
The pulmonary circulation carries blood between what two organs? | [
"kidney and heart",
"heart and pancreas",
"lungs and kidney",
"heart and lungs"
] | D | The pulmonary circulation carries blood between the heart and lungs. The systemic circulation carries blood between the heart and body. |
SciQ | SciQ-7397 | statistical-mechanics, atoms
Title: Was Lord Kelvin correct when he postulated the size of atoms? In What is Life? published in 1944, physicist Erwin Schrodinger writes the following:
Why are atoms so small? To begin with, they are very small indeed.
Every little piece of matter handled in everyday life contains an
enormous number of them. Many examples have been devised to bring this
fact home to an audience, none of them more impressive than the one
used by Lord Kelvin: Suppose that you could mark the molecules in a
glass of water; then pour the contents of the glass into the ocean and
stir the latter thoroughly so as to distribute the marked molecules
uniformly throughout the seven seas; if then you took a glass of water
anywhere out of the ocean, you would find in it about a hundred of
your marked molecules.
The following is multiple choice question (with options) to answer.
The ancient greek philosopher aristotle thought that all matter consists of just four what, which he identified as earth, air, water, and fire? | [
"compounds",
"structures",
"elements",
"ingredients"
] | C | The idea of elements is not new. It dates back about 2500 years to ancient Greece. The ancient Greek philosopher Aristotle thought that all matter consists of just four elements. He identified the elements as earth, air, water, and fire. He thought that different kinds of matter contain only these four elements but in different combinations. |
SciQ | SciQ-7398 | life, extremophiles
Title: How close to Earth's core can organisms live? We don't to know much about organisms living deep below the Earth's crust. Recently a team led by S. Giovanni discovered some microbes 300 m below the ocean floor. The microbes were found to be a completley new and exotic species and apparently they feed off hydrocarbons like methane and benzene. Scientists speculate that life may exist in our Solar System far below the surface of some planets or moons. This raises some questions:
What is the theoretical minimum distance from Earth's core where life can still exist. Please explain how you came up with this number. For example, there are temperature-imposed limits on many biochemical processes.
Is there the potential to discover some truly alien life forms in the Earth's mantle (by this I mean, life which is not carbon based, or life which gets its energy in ways we have not seen before, or non DNA-based life, or something along these lines)?
What is the greatest distance below the Earth's crust that life has been discovered? I believe it is the 300 m I cited above, but I am not 100% sure. There's a lot we don't know about life in deep caves, but we can bound the deepest living organism to at least 3.5 kilometers down, and probably not more than 30 kilometers down.
The worms recovered from deep mining boreholes are not particularly specifically adapted to live that far down: they have similar oxygen/temperature requirements as surface nematodes.
The Tau Tona mine is about 3.5 kilometers deep and about 60˚ C at the bottom. Hydrothermal vent life does just fine up to about 80˚C, and the crust gets warmer at "about" 25˚C per kilometer. It's entirely reasonable to expect life to about 5 kilometers down, but further than that is speculation.
Increasing pressure helps to stabilize biological molecules that would otherwise disintegrate at those temperatures, so it's not impossible there could be life even deeper. It may even be likely, given that the Tau Tona life breathes oxygen.
I am certain no life we might recognize as life exists in the upper mantle.
The following is multiple choice question (with options) to answer.
What are archaea that live in extremely hot environments called? | [
"tardigrades",
"hypothermic",
"thermophiles",
"hemophiliacs"
] | C | Archaea that live in extremely hot environments are called thermophiles. |
SciQ | SciQ-7399 | climate-change, carbon, water-vapour, greenhouse-gases
This doesn't really have much to do with your original question! If you want to ask about this, please go ahead and post a new question; StackExchange isn't a discussion site, and we try to keep each question focused on a single topic.
With this in mind, I'll just give a very brief answer here. Your formulation is a little inaccurate: the age of the dinosaurs spans at least 135 million years, there was a lot of carbon burial before it started, and all the carbon currently in the ground wasn't in the atmosphere at the same time. However, it is true that the Earth has seen higher CO2 levels than at present, and that much of that excess carbon is now locked up in fossil fuels. So what would happen if we put a lot of that carbon back in the atmosphere and tried to recreate the high-CO2 atmosphere that, say, T. rex breathed in the Late Cretaceous? Back then, the Earth was a lot warmer, with little or no ice at the poles. One of the biggest effects of re-releasing all that carbon would be the melting of our current polar ice sheets, raising sea levels by some tens of metres. The problem is not that the Earth will become completely uninhabitable by any life form whatsoever (although many current species will go extinct). The problem is that a lot of species, including Homo sapiens, are poorly prepared for a climate change of this magnitude. Ten percent of the world's human population and 8% of its urban land area is in low-elevation coastal zones, and would be completely submerged by a 10-metre sea-level rise -- which is still far less than the sea levels seen during the age of the dinosaurs.
Sea-level rise is just one effect among many, but for now I'll leave it at this since (as I mentioned above) this isn't related to your original question.
If a person cut his water intake in half, he will get sick before he can get fatter.
The following is multiple choice question (with options) to answer.
Warming conditions and, perhaps, human activities contributed to what fate of many organisms of the pleistocene era? | [
"extinction",
"accumulation",
"evolution",
"overpopulation"
] | A | Many of the organisms that made up the Pleistocene megafauna went extinct as conditions warmed. Some may have been driven to extinction by human activities. |
SciQ | SciQ-7400 | electrostatics, electric-fields, potential
Title: Working of a van de Graaff generator
Experiments show that when a charged conductor is placed in contact with the inside of a hollow conductor, all the charge on the charged conductor is transferred to the hollow conductor. In principal the charge on the hollow conductor and and its electric potential can be increased without limit by repetition of the process
May I know the reason for this? Will this be possible even if the potential of the hollow space is less than potential of the conductor? When the charges are on the belt they feel a repulsive force due to the electric field produced by the dome of the VdG.
Whatever is driving the belt is doing work and this results in the potential of the charges increasing as they move towards the dome.
Once inside the dome the charges on the surface of the dome no longer repel the charges on the belt.
A charge on the belt only feels the repulsive force of the other charges on the belt and so moves away from them until that force (due to the charges on the belt) becomes zero and that occurs when the charge is on the outer surface of the dome.
The following is multiple choice question (with options) to answer.
Practical limits of van de graaff generators arise because the large electric fields polarize and eventually do what to surrounding materials? | [
"decompose",
"isolate",
"displace",
"ionize"
] | D | The Van de Graaff Generator Van de Graaff generators (or Van de Graaffs) are not only spectacular devices used to demonstrate high voltage due to static electricity—they are also used for serious research. The first was built by Robert Van de Graaff in 1931 (based on original suggestions by Lord Kelvin) for use in nuclear physics research. Figure 18.38 shows a schematic of a large research version. Van de Graaffs utilize both smooth and pointed surfaces, and conductors and insulators to generate large static charges and, hence, large voltages. A very large excess charge can be deposited on the sphere, because it moves quickly to the outer surface. Practical limits arise because the large electric fields polarize and eventually ionize surrounding materials, creating free charges that neutralize excess charge or allow it to escape. Nevertheless, voltages of 15 million volts are well within practical limits. |
SciQ | SciQ-7401 | zoology, circulatory-system, heart-output, amphibians
I would add to this my notes from when I was a biochem student (but studied Zoology), mentioning the arterial cone and a spiral valve. This is better described in Britannica:
The conus arteriosus is muscular and contains a spiral valve. Again, as in lungfishes, this has an important role in directing blood into the correct arterial arches. In the frog, Rana, venous blood is driven into the right atrium of the heart by contraction of the sinus venosus, and it flows into the left atrium from the lungs. A wave of contraction then spreads over the whole atrium and drives blood into the ventricle, where blood from the two sources tends to remain separate. Separation is maintained in the spiral valve, and the result is similar to the situation in lungfishes. Blood from the body, entering the right atrium, tends to pass to the lungs and skin for oxygenation; that from the lungs, entering the left atrium, tends to go to the head. Some mixing does occur, and this blood tends to be directed by the spiral valve into the arterial arch leading to the body.
The following is multiple choice question (with options) to answer.
The remainder is transferred by contraction of what before the ventricles begin to contract? | [
"the arteries",
"the stomach",
"the atria",
"the large intestine"
] | C | |
SciQ | SciQ-7402 | cell-biology, proteins, mitosis
Title: Purpose of intensive protein synthesis in G1 phase of mitosis What is the purpose of intensive protein synthesis in G1 phase of mitosis, and what purposes do these synthesized proteins serve? Why are lipids and carbohydrates not synthesized intensively as well? The G1 phase of eukaryotic cell cycle is part of interphase, which is when the cell is replicating its DNA ready for division. To understand the need for intense protein synthesis, we first need to understand how DNA is organised during mitosis.
Before DNA is condensed into chromosomes ready for nuclear division it is in the form of chromatin, a long fiber-like structure inside the nucleus. In order to condense into chromosomes, this chromatin must undergo a process of coiling and folding in order to create the chromosome 'X' structure we are familiar with.
A major part of this DNA 'miniaturization' is the folding of the double helix around proteins called Histones - this creates new structures called nucleosomes.
In order to fully condense the roughly 3 meters of DNA in the average human cell down to a singular chromosome, millions upon millions of these Histone proteins are required.
And that answers your question; intense protein synthesis during the G1 phase is required in order to produce the extremely large amount of Histone proteins that are needed for packaging DNA into chromosomes ready for cellular division.
As for carbohydrates, these are constantly being processed by the body in order for the production of ATP for use as energy. The use of said energy for mitosis is a just another constantly required use of ATP within the body. Therefore there isn't any noticeable increase in carbohydrate processing/production, as it is happening regardless of the cell's stage in its cycle.
-See the image below (from shmoop.com) that explains the process of getting DNA into a chromosome.
The following is multiple choice question (with options) to answer.
Chromatin condenses into chromosomes during prophase, the first and longest phase of what process? | [
"apoptosis",
"meiosis",
"mitosis",
"reproduction"
] | C | The first and longest phase of mitosis is prophase . During prophase, chromatin condenses into chromosomes, and the nuclear envelope, or membrane, breaks down. In animal cells, the centrioles near the nucleus begin to separate and move to opposite poles of the cell. As the centrioles move, a spindle starts to form between them. The spindle, shown in Figure below , consists of fibers made of microtubules. |
SciQ | SciQ-7403 | 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 do plants lose the most of through the stomata? | [
"water",
"energy",
"chlorophyll",
"heat"
] | A | |
SciQ | SciQ-7404 | water, home-experiment, physical-chemistry
Argument: Oxygen is replaced by Carbon dioxide. So, there is the same amount of gas added than taken away. Therefore, heat alone most be responsible for the water level change.
Source of the Error: A simplified and wrong chemical equation is used, which does not take into account the quantitative changes. The chemical equation has to be balanced correctly. It is not true that each oxygen molecule is replaced by one carbon dioxide molecule during the burning process; two oxygen molecules result in one carbon dioxide molecule and two water molecules (which condense). Remember oxygen is present in the air as a diatomic molecule. [A reader clarifies the water condensation in an email to me as follows: If the experiment were done with the sealing fluid able to support a temperature greater than 212 F and the whole system held above this temperature then the water product of combustion would remain gaseous and the pressure within the vessel would increase as a result of three gaseous molecules for every two prior to combustion and the sealing fluid would be pushed out.]
Argument: Carbon dioxide is absorbed by the water. Thats why the oxygen depletion has an effect.
Source of the Error: This idea is triggered from the fact that water can be carbonized or that the oceans absorb much of the carbon dioxide in the air. But carbon dioxide is not absorbed so fast by water. The air would have to go through the water and pressure would need to be applied so that the carbon dioxide is absorbed during the short time span of the experiment.
Argument: The experiment can be explained by physics alone. During the heating stage, air escapes. Afterwards, the air volume decreases and pulls the water up.
Source of the Error: the argument could work, if indeed the heating of the air would produce enough pressure that some air could leave. In that case, some air would be lost through the water. But one can observe that the water level stays up even if everything has gone back to normal temperature (say 10 minutes). No bubbles can be seen.
Argument: It can not be that the oxygen depletion is responsible for the water raising, because the water does not rise immediately. The water rises only after the candle dims. If gas would be going away, this would lead to a steady rise of the water level, not the rapid rise at the end, when the candle goes out.
The following is multiple choice question (with options) to answer.
Unburned hydrocarbons can more easily be converted to carbon dioxide and water in the presence of a what? | [
"temperature",
"catalyst",
"methane",
"Ethanol"
] | B | Catalytic converters in cars increase the rates of several important reactions. Unburned hydrocarbons can more easily be converted to carbon dioxide and water in the presence of a catalyst. Additionally, carbon monoxide (a harmful gas produced by incomplete combustion of fuel) is further oxidized to carbon dioxide, and nitrous oxide compounds (which contribute to smog and acid rain) are transformed back into nitrogen and oxygen gases. By passing car exhaust over these catalysts before their release into the air, the emissions from a combustion engine are made into much less harmful substances, resulting in a much cleaner atmosphere. |
SciQ | SciQ-7405 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
What do plasmodesmata connect to in the plant cell? | [
"sporozoans",
"pores",
"cytoplasms",
"nuclei"
] | C | Plasmodesmata are gaps between plant cells, connecting the cytoplasms of plant cells. |
SciQ | SciQ-7406 | inorganic-chemistry, alloy
Title: If alloys are homogeneous mixtures, why can't we separate their components? An alloy is a material composed of two or more metals or a metal and a nonmetal. And, they are usually formed by heating the elements to their melting points, and then cooling them, so that the components mix. Now, why doesn't this works backwards i.e. if we heat the alloy again to melting point of their constituents, and they should separate? Once the alloy has been formed the atoms from the different metals will have shared there electrons with each other and come to an equilibrium. In this state the metal atoms have formed a complex structure which has a different reactivity or properties than each individual metal did in its original form .
The following is multiple choice question (with options) to answer.
What are compounds composed of only two elements called? | [
"kinetic compounds",
"binary compounds",
"symbiotic compounds",
"digital compounds"
] | B | Binary compounds are compounds composed of just two elements. The simplest kind of decomposition reaction is when a binary compound decomposes into its elements. Mercury(II) oxide, a red solid, decomposes when heated to produce mercury and oxygen gas. |
SciQ | SciQ-7407 | earth-history
Common elements in space, such as CO2, H20, CH4 and NH3 are gaseous at Earth's distance from the sun and as a result, are unlikely to stick to anything in the Earth's formation region. This is true for all 4 inner planets and likely all rocky worlds. Rocky planets likely can only form close to their star, just as gas giants, ice giants or other icy abundant bodies like comets and low-density moons, can only form further out.
Gases like the 4 above can begin to be retained around a planet after it reaches a sufficiently large mass with low enough surface temperature to retain those gases by gravity.
The boundaries where CO2, H20, CH4, NH3 and other gases can be found in the protoplanetary disk is called the frost line. Different gases have different frost lines depending on their freezing point.
It's thought that much of Earth's water, CO2, CH4 and NH3 came to the Earth by comet after the planet formed. There's still some uncertainty on the percentages, as some of those elements could have been trapped during formation.
Just to add, hydrogen and helium are obviously abundant, but will only begin to accrue around a planet of a certain mass. In our solar-system, only Jupiter and Saturn are massive enough to accrue hydrogen and helium. That's why Uranus and Neptune are relatively low on hydrogen and helium compared to the universal abundance.
Argon is in Earth's atmosphere because it forms from gradual radioactive decay of Potassium-40. Earth's Helium is also present as a result of radioactive decay.
The following is multiple choice question (with options) to answer.
What type of gases trap heat in the atmosphere, causing earth to have a moderate temperature? | [
"sulfuric gases",
"ozone gases",
"greenhouse gases",
"carbon monoxides"
] | C | Greenhouse gases trap heat in the atmosphere. This is essential so that Earth has a more moderate temperature. Without greenhouse gases, nighttime temperatures would be frigid. Natural greenhouse gases include carbon dioxide, methane, water vapor, and ozone. CFCs and some other man-made compounds are also greenhouse gases. Human activities may increase the amount of greenhouse gases, like carbon dioxide, in the atmosphere. |
SciQ | SciQ-7408 | brain
Title: Does "mind" has any physical reality in biology? Or is it just an assumptive concept? Biologically, Brain controls our thinking, ideas, decisions everything along with controlling each body parts. My question is, is there anything real as "mind "? If it's controlled by brain then how does brain controls the mind? The mind is an abstraction which arises from physical and chemical processes within the brain. For a crude analogy, think of the brain as an incredibly complex, self-modifying, multithreaded program. The mind would then be the abstraction arising from the behavior of the program as it runs. Consciousness would be the abstraction arising from the behavior of one particular thread in the program: a thread which has access to a limited buffer of its own (that thread's) behavior, and control over limited input and output from the body. All of the other (unconscious) threads may affect the conscious thread, but the conscious thread has very limited access to information about the behavior of the other threads.
Since the conscious part of the mind has access to information about its own behavior, there is actually some recursive looping going on when it comes to thinking and feeling. The feeling that this goes in circles somehow (which you seem to be expressing) is a common intuition, and it's almost certainly a correct one. But the manner in which this occurs is not well-understood, and it's definitely not well-understood within biology at the macro level because the brain is unbelievably complex and plastic. We really don't have a clue how to begin modeling the brain's processes. This is one reason artificial intelligence is still extremely crude today (despite what Elon Musk and Bill Gates may try to say).
If you want to read a scientifically-inspired theory of from whence consciousness comes, and of how it arises from the brain, I would recommend the book Godel, Escher, Bach by Douglas Hofstadter. Douglas does a good job of combining computational theory with biology, music, and art to illustrate a theory of consciousness the reader can grasp even if you don't have a strong background in any of those subjects.
The following is multiple choice question (with options) to answer.
What system is the brain the control center of? | [
"circulatory",
"nervous",
"fibrous",
"adrenal"
] | B | The brain is the control center of the nervous system. It controls virtually all mental and physical processes. |
SciQ | SciQ-7409 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
Air pollution can cause disease of what system by affecting the health of your lungs? | [
"cardiac",
"digestive",
"excretory",
"respiratory"
] | D | Air pollution is another significant cause of respiratory disease. The quality of the air you breathe can affect the health of your lungs. Asthma, heart and lung diseases, allergies, and several types of cancers are all linked to air quality. Air pollution is not just found outdoors; indoor air pollution can also be responsible for health problems. |
SciQ | SciQ-7410 | electrochemistry, redox, electrolysis
Title: In NaCl electrolysis, why does chlorine ion get oxidized but not oxygen ion? In $\ce{NaCl}$ electrolysis, on the positive electrode (aka. on the electrode where oxidation happens), $\ce{Cl-}$ ions are oxidized to $\ce{Cl2}$. But why don't we see any $\ce{O^2-}$ (naturally present in water's $\ce{OH-}$ ions) oxidized to $\ce{O^2}$ at all?
My pre-existing knowledge, may or may not be correct, that led to this question:
[1] I am under the impression that chemical reaction is a messy business in the real-world with many reactions reversible, many intermediary steps happening and many small reactions happening in the sideways. So the real-world scenario is never as neat as one clean equation.
[2] I am aware of the concept of electronegativity, and I also have feelings that
$\ce{O^2-}$ and $\ce{Cl-}$ should require a similar amount of energy input to get them oxidized. So we should really expect both reactions to happen.
With my pre-existing knowledge laid out above, I find it remarkable that not a trace of $\ce{O^2-}$ is oxidized at all. This led me to guess that the $\ce{OH-}$ ion itself may have imparted some degree of protection to the $\ce{O^2-}$ inside of it? I am afraid that as stated in another answer there is no simultaneous evolution of oxygen or chlorine during controlled electrolysis. It all depends on the concentration of ions in the solution. Keep in mind that the concentration of water is 55 M, so the ion concentration is nowhere near it no matter what you do!
The key reason is that the electrode potential of chlorine/chloride couple is quite different from that of oxidation of water, so if you have a high concentration of chloride ion, chlorine is oxidized first, once chlorine falls below a certain threshold, water begins to oxidize. Nernst equation can help in predicting that.
The following is multiple choice question (with options) to answer.
Why does the body react to a loss of chloride ions? | [
"decreased bicarbonate reabsorption",
"decreased tricarbonate reabsorption",
"increased tricarbonate reabsorption",
"increased bicarbonate reabsorption"
] | D | Chloride ions are important in neutralizing positive ion charges in the body. If chloride is lost, the body uses bicarbonate ions in place of the lost chloride ions. Thus, lost chloride results in an increased reabsorption of bicarbonate by the renal system. |
SciQ | SciQ-7411 | inorganic-chemistry, physical-chemistry, electrochemistry, electrons, electronic-configuration
one proton's positive charge attracts one electron.
The "neutral" in a neutral atom means electrically neutral.
How can a neutral atom attract electrons when it's supposed to have zero charge ? The answer lies in electronegativity. When a proton attracts an electron, the electron doesn't magically suck out the charge of the proton. The proton's charge is still distributed in all directions. The reason why 1 proton on average can attract only 1 electron is because electrons push each other out.
Now let's first take H - it has 1 proton which attracts 1 electron. If another electron jumps in, only 1 electron stays in the end. Then He - it has 2 protons, so it attracts electrons even more. So even though electrons are fighting for the place, the nucleus charge is enough to hold them.
It gets interesting with Li. It should have 3 electrons, right? But 1st shell can take only 2 electrons, so the 3d electron must go to the 2nd shell which is further away. In such case the inner shell of electrons has a much greater effect on the outer electron, this is called electron screening, not to mention that the further you are from nucleus - the weaker the attraction. So even though Li has more protons than He, it's too weak to hold electrons on the 2nd shell, so some other atom will take the electron away and Li will be ionized and become Li$^+$ with only 2 electrons.
How strongly an atom wants new electrons is called electronegativity. It increases to the right of the periodic table because nucleus gets larger and larger and can hold on more and more electrons. In the last columns atoms want electrons so much that they can mug other atoms with weaker electronegativity.
But then the row of the table finishes and new row starts. At this point previous shell is completely filled and a new shell starts, and the electron screening kicks in again.
You can see these trends here. Electronegativity is the reason why Na & Cl can't form a molecule (covalent bond) - Cl (strong electronegativity) simply takes Na's (weak electronegativity) electron and both become ions: Cl$^-$ and Na$^+$. In the end they form an ionic bond instead.
The following is multiple choice question (with options) to answer.
The negatively charged electrons are attracted to the positively charged what? | [
"ion",
"nucleus",
"axon",
"atom"
] | B | |
SciQ | SciQ-7412 | 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.
Most of the gray matter is on the surface of the brain, surrounding what other type of matter? | [
"corrugated",
"blue",
"white",
"dark matter"
] | C | |
SciQ | SciQ-7413 | thermodynamics, geophysics
With supercooled water, this effect is even more pronounced - a water at -30 °C has about the same density as water at 60 °C.
Oceans cool mostly by evaporation - the surface layers of water "spontaneously" changing state from liquid to gaseous. You get a balancing act between energy lost to evaporation, and incoming sunlight. However, there's a huge gap between the surface and the deeps, a lot of water mass - the incoming sunlight is nowhere near enough to warm ocean waters throughout. So you get warm surface waters, then a gradient of cooler and cooler water, and finally about 0-3 °C in the deep. To illustrate how big this gap is, about 90% of the worldwide ocean water is in the 0-3 °C range (hence the "nowhere near enough sunlight to heat the whole thing through").
Of course, a 4 °C body of water is great for cooling systems running at 40 °C and more. Air is actually a pretty good insulator, so air cooling gets tricky with large systems. Water, on the other hand, is pretty thermally conductive, and it easily convects, so cooling a huge data centre becomes almost trivial.
EDIT:
Let me address the Sun part, since there seems to be some confusion there as well.
Nuclear fusion is something that happens very infrequently. Two nuclei must come very close together to fuse, and they need enough kinetic energy to overcome the repulsion between each other (since both have the same electric charge).
The first problem is solved by increasing density. The more nuclei you have in the same volume, the higher the likelihood of close contact. This is where pressure comes in - that's how you get a higher density. Stars are made of plasma, and plasma is easily compressible, similar to a gas, so as pressure increases, so does density. How compressed is it? Well, the Sun's core, where the fusion reactions are actually happening, contains 34% of the Sun's mass, in only 0.8% of the Sun's volume. In the centre, the density is around 150 times the density of liquid water. The pressure is about 100 000 times the pressure in the Earth's core, and about 100 000 000 times the pressure of the water on the bottom of the Mariana trench.
The following is multiple choice question (with options) to answer.
Cooling or evaporation of what from the sea surface makes surface water dense? | [
"warm water",
"salt water",
"fresh water",
"dirty water"
] | C | Cooling or evaporation of fresh water from the sea surface makes surface water dense. This causes the surface water to undergo downwelling. |
SciQ | SciQ-7414 | embryology
Title: What is a zygote? During fertilization, the nuclear membrane of the pro-nucleus of the ovum and sperm degenerate. Is the cell is stage called a zygote?
After the dissolution, mitosis occurs and two cells are formed.Or is the cell is stage called a zygote?
I'm confused as i knew a zygote was single-celled. Conventionally, a zygote is considered to be formed the moment that a spermatozoum, penetrates the cell membrane of the ovum and yields its genetic material into the ovum. Effectually, however, there is a lag between the instant of fertilization and the fusion of the male and female pronuclei. In mammals, the duration of this lag period is ~12 hours. There are also additional actions that must be completed before the first mitosis as in most mammals, including humans, the ovum is actually in the second metaphase of meiosis at the time of fertilization.
The following is multiple choice question (with options) to answer.
What is the term for reproductive cells, such as sperm and egg? | [
"parasites",
"nucleus",
"gametes",
"spores"
] | C | Sexual reproduction combines gametes from two parents. Gametes are reproductive cells, such as sperm and egg. As gametes are produced, the number of chromosomes must be reduced by half. Why? The zygote must contain genetic information from the mother and from the father, so the gametes must contain half of the chromosomes found in normal body cells. When two gametes come together at fertilization, the normal amount of chromosomes results. Gametes are produced by a special type of cell division known as meiosis . Meiosis contains two rounds of cell division without DNA replication in between. This process reduces the number of chromosomes by half. |
SciQ | SciQ-7415 | biophysics, stress-strain, material-science
How would the prosthetic element be made?.. that is the more important question. Devil is in the detail.. or so one views design with composites. No over/undesign is permissible. Material should not be where it is not required without a functional requirement. Material should be placed in the right amount and and in the right direction.
As one possibility a carbon cloth with more layers at extremities should be rolled and inserted into a metal mould cavity and hot resin cured. A design/FEM analysis is needed after considering FMECA which are medically well known. Loads and their combination at neck of ball/socket/pelvis joint should be known. Torsional strength required at knee cap may need Silicone rich pockets for shock absorption in the vicinity of the two joints.
Downsides with carbon/graphite fiber composite depend upon conformance of the degree of stiffness in multiaxial stress distribution.
May be 3d printing of ceramics provides a better stress conduction path than using injection moulding or cloth moulding carbon/graphite for stiffness flexibility and grain direction control.
The following is multiple choice question (with options) to answer.
What material is regularly used in human hip and knee implants? | [
"wood",
"metal",
"glass",
"coal"
] | B | Metal is regularly used in the human body for hip and knee implants. Most implants need to be replaced over time because, among other things, metal does not bond with bone. Researchers are trying to find better metal coatings that would allow metalto-bone bonding. One challenge is to find a coating that has an expansion coefficient similar to that of metal. If the expansion coefficients are too different, the thermal stresses during the manufacturing process lead to cracks at the coating-metal interface. Another example of thermal stress is found in the mouth. Dental fillings can expand differently from tooth enamel. It can give pain when eating ice cream or having a hot drink. Cracks might occur in the filling. Metal fillings (gold, silver, etc. ) are being replaced by composite fillings (porcelain), which have smaller coefficients of expansion, and are closer to those of teeth. |
SciQ | SciQ-7416 | statistical-mechanics, atmospheric-science, density
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake waters, forming a gas cloud that can suffocate wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can be a trigger for such phenomenon. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes.
Picture 1: one of a number of cattle killed by a limnic eruption at Lake Nyos, Cameroon.
We can occasionally prevent the buildup of carbon dioxide by degassing the body of water.
Picture 2: a siphon used by French scientists to de-gas Lake Nyos. The carbon dioxide emerges from its deposits and bubbles into the water, floating to the top.
The following is multiple choice question (with options) to answer.
What are the most dramatic, sudden, and dangerous types of mass wasting? | [
"volcanoes",
"earthquakes",
"landslides",
"monsoons"
] | C | Landslides are the most dramatic, sudden, and dangerous types of mass wasting. Landslides are sudden falls of rock; by contrast, avalanches are sudden falls of snow. |
SciQ | SciQ-7417 | homework-and-exercises, electromagnetism
Title: Current Carrying Coil - Torque i'm stuck on how to answer the last part of this question and would really appreciate some pointers.
A rectangular coil (sides $a = 15 \, \mathrm{cm}$ and $b = 20 \, \mathrm{cm}$, $m= 15 \, \mathrm{g}$), is suspended by one
of its shorter sides, and lies in a vertical plane due to its weight. The coil carries a
current $I = 3 \, \mathrm{A}$, directed counterclockwise. If a uniform magnetic field $B = 0.06 \, \mathrm{T}$
directed upwards is switched on, the coil rotates around the $x$ axis until it reaches a
new equilibrium position (see figure). Determine:
(a) the magnitude of the magnetic moment of the coil;
(b) the torque acting on the coil when the coil is in a vertical position;
(c) the angle that the coil forms with the vertical axis when the coil reaches the
equilibrium position.
The following is multiple choice question (with options) to answer.
What current-carrying long coil of wire acts as a magnet? | [
"igniter",
"antenna",
"solenoid",
"converter"
] | C | Magnetic Field Produced by a Current-Carrying Solenoid A solenoid is a long coil of wire (with many turns or loops, as opposed to a flat loop). Because of its shape, the field inside a solenoid can be very uniform, and also very strong. The field just outside the coils is nearly zero. Figure 22.40 shows how the field looks and how its direction is given by RHR-2. |
SciQ | SciQ-7418 | gas-phase-chemistry
Title: Is there any kind of reaction with two types of reactants (gases) and one product (also gas) such that the total volume after the reaction increases? I would like to think of the following equation:
$$\ce{aA(g) + bB(g) -> cC(g)}$$
where $a + b < c$ and $\ce{A},$ $\ce{B}$ and $\ce{C}$ are different gases.
Is there such chemical reaction? This is a fun question. The essence of what makes it challenging is that you're doing a synthesis -- combining two different species into one -- yet ending up with more particles, not (as is typical) less. This limits the number of possible reactions significantly. Here, however, is one that meets the conditions:
Octasulfur ($\ce {S_8}$) boils at 444.6 $^\circ \text{C}$ at standard pressure. So, above that temperature, one could have:
$$\ce{ S_{8(g)} + 4O_{2(g)}-> 8SO_{(g)}},$$
where $1+4 < 8$.
Of course, if octasulfur were combusted with oxygen, it's likely that many other species of sulfur oxides (i.e., compounds of the form $\ce {S_xO_y}$) would be produced as well.
The following is multiple choice question (with options) to answer.
In combination or synthesis reactions, two chemical species combine to produce a what? | [
"alloy",
"fusion",
"new compound",
"mixture"
] | C | In combination or synthesis reactions, two chemical species combine to produce a new compound. The general expression for a combination reaction is:. |
SciQ | SciQ-7419 | astrophysics, stellar-physics, supernova, stellar-evolution
Title: Why does a supernova explode? This is really bugging me. When you look up some educational text about stars life, this is what you find out:
Gravity creates the temperature and pressure to start fusion reactions.
The fusion proceeds to heavier and heavier cores ending with iron, which remains in the centre of the star.
One moment, all light cores are depleted and the gravity wins over the power of the fusion reactions, now absent.
The core of the star collapses into high density object, which may vary depending on the star mass.
And the top layers of the star explode.
And I just cannot find clear explanation why. According to what I imagine, the top layers of the star should just fall into the collapsing core.
Is that because of the 3rd Newtons rule?
Or do the stars have some need to end with a cool boom? There are lots of possible ways that stars can end their life, even in the subset of cases where the end is violent. Eloff has given an excellent answer, but I wanted to add a few points.
Summary (tl;dr):
You need the right conditions (mass, angular momentum, metallicity, etc) to produce a proto-neutron-star which is able to resist complete collapse to a black-hole. The bounce from hitting that proto-neutron-star surface, and the heating from neutrinos, is what drives the explosion of material. Radioactivity is eventually the source of the light we see from supernovae.
The basic picture for producing a supernova from a massive star1:
The following is multiple choice question (with options) to answer.
The core of a star collapses during what event, forming a neutron star? | [
"blast",
"spark",
"gravitational",
"supernova"
] | D | The average particle energy needed to observe 19 GeV . (a) What unification of forces is estimated to be 10 is the rest mass in kilograms of a particle that has a rest mass 19 of 10 GeV/c 2 ? (b) How many times the mass of a hydrogen atom is this? 14. The peak intensity of the CMBR occurs at a wavelength of 1.1 mm. (a) What is the energy in eV of a 1.1-mm photon? (b) 9 There are approximately 10 photons for each massive 9 particle in deep space. Calculate the energy of 10 such photons. (c) If the average massive particle in space has a mass half that of a proton, what energy would be created by converting its mass to energy? (d) Does this imply that space is “matter dominated”? Explain briefly. (a) What Hubble constant corresponds to an approximate 10 age of the universe of 10 y? To get an approximate value, assume the expansion rate is constant and calculate the speed at which two galaxies must move apart to be separated by 1 Mly (present average galactic separation) in a time of 10 10 y. (b) Similarly, what Hubble constant corresponds to a 10 universe approximately 2×10 -y old? 16. Show that the velocity of a star orbiting its galaxy in a circular orbit is inversely proportional to the square root of its orbital radius, assuming the mass of the stars inside its orbit acts like a single mass at the center of the galaxy. You may use an equation from a previous chapter to support your conclusion, but you must justify its use and define all terms used. The core of a star collapses during a supernova, forming a neutron star. Angular momentum of the core is conserved, and so the neutron star spins rapidly. If the initial core radius 5 is 5.0×10 km and it collapses to 10.0 km, find the neutron star’s angular velocity in revolutions per second, given the core’s angular velocity was originally 1 revolution per 30.0 days. Using data from the previous problem, find the increase in rotational kinetic energy, given the core’s mass is 1.3 times that of our Sun. Where does this increase in kinetic energy come from? 19. Distances to the nearest stars (up to 500 ly away) can be measured by a technique called parallax, as shown in Figure 34.26. What are the angles θ 1 and θ 2 relative to the plane of the Earth’s orbit for a star 4.0 ly directly above the Sun? 20. (a) Use the Heisenberg uncertainty principle to calculate the uncertainty in energy for a corresponding time interval of. |
SciQ | SciQ-7420 | evaporation, humidity
Title: Confusion understanding relative humidity levels I have difficulty in understanding how can the relative humidity of a mixture of air and water can be 100%. I understand that places like where i live have high relative humidity, so the place is more humid (rain forest) than deserts, for exemple. But an evaporator, in an air conditioning system, removes the water from the air passing in and elevates the relative humidity of it. So why does a mixture containing, for example, 50% of relat. humidity can lose water mass from it and have a highier relat. humidity level?
Thanks :) For a given temperature and pressure, there is a maximum amount of water vapor which can exist in gaseous form. Any greater concentration will cause some of the vapor to condense. Measuring the absolute amount of vapor in the air produces absolute humidity, which is not expressed in per cent.
Relative humidity, however, is the amount of water vapor relative to the theoretical maximum at that temperature and pressure - that's why it's called relative. It is defined as the ratio of the two concentrations expressed as a percentage. So if the air contains the maximum amount of water vapor that it can hold without any condensing, the relative humidity is, by definition, 100%.
The following is multiple choice question (with options) to answer.
What is the term used for a large body of air of the same temperature and moisture conditions? | [
"air pool",
"air mass",
"sky mass",
"air group"
] | B | An air mass is a large body of air that has about the same conditions throughout. For example, an air mass might have cold dry air. Another air mass might have warm moist air. The conditions in an air mass depend on where the air mass formed. |
SciQ | SciQ-7421 | muscles, lungs, human-physiology
Title: Why is there smooth muscle in our bronchioles? Having muscle tissue in our bronchioles that can constrict seems like a poor choice for tissue. Why would our airway want to ever close up? Wouldn't it be more beneficial for our bronchioles to just remain open? There are at least two things to consider.
First, ability to limit airflow is a defense mechanism for animal. Imagine getting into area of some sort of toxic evaporation, e.g. CO2 cloud near volcano , then it makes sense to decrease delivery of toxin via lungs to minimum. As I understand, that is what an allergic asthma attack. (Sorry for not providing good enough source of that)
Secondly, you are incorrect in assuming that normal state is "dilated". Dilation of branchioles is sympathetic ("fight-and-fly") response of the nervous system to something like danger, that requires short-term boost in energy production. That is, by default, your airflow is limited. Probably, to limit amount of energy you effectively burn via oxygenation. But most importantly, you leave yourself a reserve in terms of oxygen supply for critical moments.
Some more information you might find here.
The following is multiple choice question (with options) to answer.
The loss of oxygen to the heart muscle causes that part of the tissue to what? | [
"thrive",
"beat erratically",
"die",
"beat harder"
] | C | The image below shows the way in which a blocked coronary artery can cause a heart attack. The loss of oxygen to the heart muscle cause that part of the tissue to die. Maybe one day, stem cell therapy will allow for the replacement of the dead cells with new cardiac muscle cells. |
SciQ | SciQ-7422 | cell-biology, nutrition, blood-circulation, liver
Title: How do nutrients get to the cells they need to get to? I understand the basics of digestion. I know that nutrients get absorbed by the microvilli, enter the bloodstream and travel to the liver but after all that, what is the biological mechanism that guides these nutrients to the proper receiving location? Broadly speaking, nutrients that enter the blood from the gut, and those that are released into the blood by the liver, are available to any cells that require them. So there is no "guiding to the correct location" in the sense that you suggest.
Lipids for example are present in the various lipoproteins and can be acquired from these by all cells. Iron is bound to transferrin, and any cell with transferrin receptors can internalise the transferrin and take the iron. Glucose is available in solution in the plasma, and free fatty acids are bound to serum albumin in the blood. During starvation the liver produces ketones ("ketone bodies") which are taken up by many different tissues/cell types.
The following is multiple choice question (with options) to answer.
What system transports many substances to and from cells throughout the body? | [
"circulatory",
"physiological",
"cardiovascular",
"nutritional"
] | C | The cardiovascular system transports many substances to and from cells throughout the body. |
SciQ | SciQ-7423 | solubility, precipitation
$$\ce {Fe^{3+} + 2H2O <=> [FeOH]^{2+} + H3O+ }$$
Thus, $\ce{H3O+}$ ions in solution can react with added $\ce{CO3^{2-}}$ ions to form carbonic acid $(\ce{H2(CO3)3})$,which can decomposed to form $\ce{CO2}$ and $\ce{H2O}$. Remaining $\ce{Fe^{3+}}$ will combine with left behind $\ce{OH-}$ ions to make $\ce{Fe(OH)3}$, which would decomposed to $\ce{Fe2O3}$. Thus, when $\ce{Na2CO3}$ is added to an aqueous solution of $\ce{FeCl3}$, one can expect the following sequence of reactions to be taken place:
$$\ce {FeCl3 (aq) + Na2CO3 (aq) -> [Fe2(CO3)]^{3+} (aq) -> Fe2O3 (s) + CO2 (g) + H2O (l)}$$
The following is multiple choice question (with options) to answer.
What consists of two or more elements and forms as a result of a chemical reaction? | [
"protein",
"compound",
"particle",
"molecule"
] | B | Living things consist of matter, which can be an element or a compound. A compound consists of two or more elements and forms as a result of a chemical reaction. |
SciQ | SciQ-7424 | cardiology, medicine
Title: What does irregular heartbeat mean in simple language? I bought a blood pressure monitor (A&D UA-851) which has the option to measure irregular heartbeat. I do understand what 'irregular' means, but why do irregular heartbeats happen and what are it's implications short and long term? The normal cardiac cycle is comprised of two distinct phases: the systolic phase in which the heart contracts, ejecting the blood, followed by the the diastolic phase when the cardiac muscle relaxes, refilling the heart with blood.
This cycle is assured by specialised cardiomyocytes (Cardiac muscle cells) that conduct electrical impulses through the heart. When there's interference in this electric activity, the cycle becomes irregular or arrhythmic.
Arrhythmias can be divided by their place of origin:
Atrial (atria are the upper chambers of the heart)
Ventricular (ventricles are lower chambers of the heart)
Junctional (the junction between the two)
Heart blocks (caused by a blockade in the conductivity of the electrical specialised cardiomyocytes)
Some arrhythmias are physiological, such as the Respiratory sinus arrhythmia, a naturally occurring variation in heart rate that occurs during a breathing cycle. Also, in healthy individuals, some extra sistoles might occur without being the translation of a subjacent heart condition and have benign prognosis in individuals without other conditions.
However, some arrhythmias can have a wide range of health implications, from asymptomatic, to a mild intolerance to exercise, to Cerebrovascular Accident (CVA or stroke) or even sudden death due to cardiac arrest.
Therapeutic varies with the underlying cause but can be medical (with drugs such as Na+, K+ and Ca+ channel blockers, beta-blockers and Digoxin) or surgical (ie: Artificial pacemaker).
The following is multiple choice question (with options) to answer.
What is occasional chest pain known as? | [
"angina pectoris",
"heart murmur",
"arrhythmia",
"cardiac arrest"
] | A | |
SciQ | SciQ-7425 | biochemistry, gas-laws
Title: What is the state of aggregation (gas, liquid) of oxygen in blood? Atmospheric oxygen is in O2 and a gas. Then we inhale the air, our efficient lungs do the magic to filter out the oxygen and push them into the blood stream.
When we say hemo and globin transport the oxygen using the iron ions. In what state oxygen is transported in the blood? as a gas or a liquid or an ion? It is hard for me to conceive of the idea that oxygen would be in gaseous form in the blood. "GAS in blood?" e.g. Arterial Blood Gas Test
Also, how does the lungs convert the gas into something that is compatible to be in blood?
References:
Amount of Oxygen in the Blood Regarding the state of oxygen in blood: It is in solution in the blood plasma (which mostly consists of water), in the form of single molecules. Think of water which you leave exposed to air: carbon dioxide will be captured and dissolved (along with the other gases in air), but these molecules are not gaseous or liquid, but rather "in solution", which is different from the "classical" states.
Back to oxygen: As your reference already states, most of the oxygen in solution will bind to hemoglobin. The actual state of oxygen in that complex has been debated, but it is believed to be reduced by the hemoglobin iron to the superoxide anion, coordinated to Fe$^{3+}$. See Wikipedia on this.
Also, the lungs do not "convert" the atmospheric oxygen to anything, they rather allow, due to their very large surface area, the quick exchange of oxygen/carbon dioxide in solution and in the air.
The following is multiple choice question (with options) to answer.
In the cardiovascular system, where is the ultimate destination of the oxygen-poor blood? | [
"liver",
"brain",
"heart",
"lung"
] | C | Systemic circulation is the longer loop of the cardiovascular system. It carries blood between the heart and the rest of the body. Oxygen-rich blood flows from the heart to cells throughout the body. As it passes cells, the blood releases oxygen and absorbs carbon dioxide. Then the oxygen-poor blood returns to the heart. |
SciQ | SciQ-7426 | special-relativity, mass-energy
Title: How does matter turn to energy at the atomic level? When matter is converted to energy by means of $E=mc^2$, it produces quite a lot of "energy".
What I am having trouble understanding is exactly how the matter is transformed to energy at the atomic level. Do the atoms gain something or lose something in their internal structure? Do they just vibrate at different frequencies when the conversion occurs?
Edit: This is a duplicate of the question, pardon me. Sorry. Let us get down to basics, to convert matter to energy the special relativity algebra has to be used. This describes elementary and complex particles by a four vector, whose "length" is the invariant mass of the system described, invariant to Lorenz transformations.
The length of this 4-vector is the rest energy of the particle. The invariance is associated with the fact that the rest mass is the same in any inertial frame of reference.
The $M$ in the famous $E=Mc^2$ coincides with the invariant mass only in the rest frame of the particle/system, because this $M$ is a function of velocity and is called the relativistic mass and has nothing to do with the energy budget of particles, except at the rest frame of the system.
The fact that energy can be extracted from particles and systems with an invariant mass depends on the quantum mechanical nature of atoms. Atoms are composed out of electrons trapped in the electric potential well of the nucleus, in stable orbitals, , but the energies stored are of order of keV, not really exploitable, also because the orbitals are stable.
A lot of energy can exist in a nucleus , order of MeV, where neutrons, protons, are bound by the strong force in potential wells, and also where there also exist instabilities that can be exploited, by forcing changes in nuclear structure, i.e. the type and number of nucleons.
This is the binding energy curve
for the nuclei. It gives for each known nucleus the average binding energy per nucleon, in the collective strong potential well. The fact that one can extract energy from transitions is based on this curve.
The following is multiple choice question (with options) to answer.
What is the study of the energy transformations that occur in a collection of matter? | [
"thermodynamics",
"kinetics",
"geophysics",
"fluctuations"
] | A | |
SciQ | SciQ-7427 | statistical-mechanics, atmospheric-science, density
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake waters, forming a gas cloud that can suffocate wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can be a trigger for such phenomenon. Lakes in which such activity occurs may be known as limnically active lakes or exploding lakes.
Picture 1: one of a number of cattle killed by a limnic eruption at Lake Nyos, Cameroon.
We can occasionally prevent the buildup of carbon dioxide by degassing the body of water.
Picture 2: a siphon used by French scientists to de-gas Lake Nyos. The carbon dioxide emerges from its deposits and bubbles into the water, floating to the top.
The following is multiple choice question (with options) to answer.
Love canal was an infamous example of what type of pollution? | [
"Land Pollution",
"industrial waste dumping",
"thermal pollution",
"Visual Pollution"
] | B | Disposing of industrial waste is one way that human actions pollute the land. This became clear more than 30 years ago in Love Canal, a neighborhood in Niagara Falls, New York. Love Canal may sound lovely, but it is not. Love Canal was and is a disaster. Love Canal been called one of the worst environmental disasters of all time. |
SciQ | SciQ-7428 | waves, atmospheric-science, turbulence
Title: What is the relevant phenomenon behind Undulatus/Radiatus cloud formations? I am seeing many people claiming that cumulus clouds that sometimes form periodic wavy patterns (see images for "altocumulus undulatus" or "Radiatus" for instance) have no explanation aside from being chemtrails, and I'd like to be able to respond with a sound scientific explanation.
I'd like to understand the phenomenon and my guess is that it's about the cloud blanket being forced by winds with the result of a periodic pattern appearing, much like sand waves form in shallow water at the beach.
But is it really the case? Searching for a more detailed explanation I ran into Tollmien-Schlichting waves that are a path to turbulence, but I admit I did not understand much, so here is my question(s):
What is the physics behind such cloud formations? And
Given an estimate of the spatial period of these cloud waves and the cloud height, can one infer the windspeed at that height? There are a variety of cloud wave patterns, including radiatus, undulatus, and gravity wave clouds. Their causes are not mysterious, but fluid mechanics is rarely simple. When air rises and falls in a pattern, clouds form at the high points if the air reaches the lifted condensation level. The spatial period of the clouds does not in general depend just on wind speed and height, so they cannot easily be used to estimate the wind speed at height.
Radiatus clouds (also known as "cloud streets" or "horizontal convective rolls") are lines of thermal-updraft-top clouds which form parallel to the wind direction. The wind lines up the convective cells to form horizontal convective rolls as shown in this image from Wikipedia:
The following is multiple choice question (with options) to answer.
What is a funnel-shaped cloud of whirling high winds known as? | [
"volcano",
"tsunami",
"tornado",
"hurricane"
] | C | Severe thunderstorms have a lot of energy and strong winds. This allows them to produce tornadoes. A tornado is a funnel-shaped cloud of whirling high winds. You can see a tornado in Figure below . The funnel moves along the ground, destroying everything in its path. As it moves it loses energy. Before this happens it may have gone up to 25 kilometers (16 miles). Fortunately, tornadoes are narrow. They may be only 150 meters (500 feet) wide. |
SciQ | SciQ-7429 | mass, velocity, weight
Wind stroke and area of existing large flying birds (and Haast Eagles) are approximately optimum for the load.
Modern materials will allow flying-related swept area per mass to be as good as or better than nature has achieved in these large birds.
This violates the usual cube-squared law that usually requires scaled-up versions of a given creature to be substantially more sturdy and thick-boned, and scaled-down versions to be much more "delicate". This is because the volume and (more or less) the mass changes with dimension cubed but areas such as bone cross-section to change with dimension squared. So a linearly scaled-up ant of elephant size would break apart under its own weight and muscle forces and a linearly scaled-down elephant of any size would be vastly too massive for its energy and power capabilities.
Feather size scales at most linearly with dimension squared - ie a Haast Eagle scaled up to man mass size would have feathers in the same proportion to size as on the original, or smaller.
Wing design will be "something like" the best examples available in nature. While many people probably thing that they could greatly improve on current designs, the experience base is very limited compared to the competition and so far design successes are few.
The following is multiple choice question (with options) to answer.
Why do birds need a light-weight body? | [
"to stay aloft",
"for cooling",
"water flotation",
"food shortages"
] | A | Birds need a light-weight body in order to stay aloft. Even so, flying is hard work, and flight muscles need a constant supply of oxygen- and nutrient-rich blood. The organ systems of birds are adapted to meet these needs. |
SciQ | SciQ-7430 | human-biology, biochemistry, molecular-biology, cell-membrane, pulmonology
Title: How does lipoid pneumonia lead to acute respiratory distress syndrome (ARDS)? How does lipoid pneumonia lead to acute respiratory distress syndrome (ARDS)?
The vaping illnesses that have been happening on the news in the United States are being caused by the federal prohibition on marijuana. Smugglers will legally go to recreational marijuana dispensaries in legal states and purchase cartridges that contain about a gram of "wax". Proper cartridges will use polyethylene glycol, polypropylene glycol, or vegetable glycerin to suspend the THC for vaporizing, but the smugglers have been known to open up the tank and remove some of the wax and refill the remaining volume with Vitamin E Oil. These tampered cartridges are then sold on the black market to recreational and medical consumers in illegal states.
The CDC Report: "Outbreak of Lung Injury Associated with the Use of E-Cigarette, or Vaping, Products"
Edit: So, I was on some conspiracy shtuff when I wrote this post because I was worried about impurities in my vapes killing me. I don't want to take this down because I want my cognitive distortion to remain visible as a reminder of how we can succumb to biased reasoning. Also, the answer I marked correct contextualized the fragmented information of which I was aware and attempted to give me an improved framework for understanding the terms I was using incorrectly as a layman. There are several ways to get ARDS (sepsis, pneumonia, trauma, pancreatitis, etc). Pathophysiologically, they all converge at alveolar insult. So however it happens, there's alveolar insult, cytokine release that recruits neutrophils, and the activated neutrophils release toxic mediators that destroy the alveolar membranes. So for your question specifically, the mineral oil in the vape cartridges (theoretically) is instigating an inflammatory reaction that destroys alveolar membranes.
The following is multiple choice question (with options) to answer.
Asthma, pneumonia, and emphysema are diseases of what system? | [
"pulmonary",
"digestive",
"respiratory",
"reproductive"
] | C | Diseases of the respiratory system include asthma, pneumonia, and emphysema. |
SciQ | SciQ-7431 | newtonian-mechanics, forces, rotational-dynamics, reference-frames, torque
Of course, when the time constants of all of these spring is short, as it is with the kinds of interactions we are interested in here, this real behavior gets close and closer to a "rigid body" like behavior. Indeed, what we can show is that this "rigid body" style rotation is one example of what happens when you assume that physics is local. If you assume that a piece of the object only "knows" things in the neighborhood of that piece, you find there is no way to avoid rotation. To have the object translate directly away from you when you push off-center requires that far parts of the object instantly "know" the correct direction to travel.
The following is multiple choice question (with options) to answer.
The “knee-jerk" motion that people involuntarily perform after being struck in the knee in a certain way is an example of what kind of behavior? | [
"reflex",
"spasm",
"sensor",
"reaction"
] | A | Innate Behaviors: Movement and Migration Innate or instinctual behaviors rely on response to stimuli. The simplest example of this is a reflex action, an involuntary and rapid response to stimulus. To test the “knee-jerk” reflex, a doctor taps the patellar tendon below the kneecap with a rubber hammer. The stimulation of the nerves there leads to the reflex of extending the leg at the knee. This is similar to the reaction of someone who touches a hot stove and instinctually pulls his or her hand away. Even humans, with our great capacity to learn, still exhibit a variety of innate behaviors. |
SciQ | SciQ-7432 | -
Thanks for your answer. Do you think there is a way to salvage my approach above? – Benja Aug 26 '12 at 7:25
@BenjaLim I'm not sure. I just saw this approach and ran with it, since I really really like tori. – Alex Becker Aug 26 '12 at 7:26
@BenjaLim I re-read your post and noticed you asked us not to post complete solutions. Sorry! I missed that the first time around. I suppose the damage is done now. – Alex Becker Aug 26 '12 at 7:46
It's ok as I don't think I can use your approach above anyway. I am in the process of trying to show that the image of $H$ under the projection is a discrete space, because from there I think my problem will follow. – Benja Aug 26 '12 at 7:48
@BenjaLim I think sentences 3 and 4 in my answer should help with showing that. – Alex Becker Aug 26 '12 at 8:02
show 3 more comments
The following is multiple choice question (with options) to answer.
What are tiny, hair like projections? | [
"cilia",
"actin",
"spinicles",
"fuzz"
] | A | Many mucous membranes are also covered with cilia. These are tiny, hair-like projections. Cilia move in waves and sweep mucus and trapped pathogens toward body openings. You can see this in the diagram in Figure below . When you clear your throat or blow your nose, you remove mucus and pathogens from your body. |
SciQ | SciQ-7433 | earth, amateur-observing, fundamental-astronomy
Title: Does weight influence Earth's spin? If put enough weight on a particular point on Earth's surface disturbing the balance between hemispheres, is it possible that the Earth's spin could change like an unbalanced spinning top? The Earth does spin like an unbalanced top. The Earth's rotation axis is not fixed. It instead moves in a complex manner due to a combination of external torques exerted by the Moon and Sun, a torque-free nutation due to the oblate shape of the Earth, and also due to changes on and in the Earth.
The torque-induced motions are called precession and nutation, distinguished by period. The largest and slowest of these motions is the axial precession. This causes the Earth's rotation axis to trace out a cone over the course of 26000 years.
(source: nasa.gov)
The torque-induced nutations are also cyclical motions induced by the Moon and the Sun. These are much smaller in magnitude and have a much shorter period. The largest of these has a magnitude of about 20 arc seconds and a period of 18.6 years. All other nutation terms have much smaller magnitude and have shorter period.
The torque-free nutation would have a period of about 305 days if the Earth was solid. The oceans, the atmosphere, and the outer core alter this. The Chandler wobble has a period of about 433 days and a magnitude of less than an arc second. Because the Chandler wobble isn't as predictable as are precession and nutation, it's lumped into a catch-all category called "polar motion." The redistribution of water over the course of a year (e.g., snow on Siberia in the winter but not in the summer) results in a yearly component of the polar motion.
There are lots and lots of other factors, all small. Polar motion is observed after the fact.
The following is multiple choice question (with options) to answer.
How long does it take for the earth to make a complete rotation of its axis? | [
"24.25 hours",
"24 hours",
"one year",
"one month"
] | B | |
SciQ | SciQ-7434 | climate-change, ice-age
Title: Was there a period of global warming before the start of the last ice age? I am curious to know if there was a period of global warming that took place before the start of the last ice age and I would like to know how long this period of global warming lasted. There was an interglacial befor the last glaciation:
glacial–interglacial cycles last ~100,000 years (middle, black line) and consist of stepwise cooling events followed by rapid warmings, as seen in this time series inferred from hydrogen isotopes in the Dome Fuji ice core from Antarctica
NOAA
The following is multiple choice question (with options) to answer.
Glaciers have been melting since what period? | [
"bronze age",
"industrial age",
"pleistocene ice age",
"stone age"
] | C | Glaciers and ice sheets are melting. This can be seen clearly in photographs. The glaciers advanced during the Pleistocene ice age. They have been melting back since then, except for during the Little Ice Age. However, the rate of melting has increased tremendously in recent decades. |
SciQ | SciQ-7435 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
The transmission electron micrograph shows the cell walls where two cells do what? | [
"disappear",
"split apart",
"come together",
"reproduce"
] | C | |
SciQ | SciQ-7436 | mineralogy, hydrogeology, mars
Despite active transport into Earth’s mantle, water has been present on our planet’s surface for most of geological time. Yet water disappeared from the Martian surface soon after its formation. Although some of the water on Mars was lost to space via photolysis following the collapse of the planet’s magnetic field, the widespread serpentinization of Martian crust suggests that metamorphic hydration reactions played a critical part in the sequestration of the crust. Here we quantify the relative volumes of water that could be removed from each planet’s surface via the burial and metamorphism of hydrated mafic crusts, and calculate mineral transition-induced bulk-density changes at conditions of elevated pressure and temperature for each. The metamorphic mineral assemblages in relatively FeO-rich Martian lavas can hold about 25 per cent more structurally bound water than those in metamorphosed terrestrial basalts, and can retain it at greater depths within Mars. Our calculations suggest that in excess of 9 per cent by volume of the Martian mantle may contain hydrous mineral species as a consequence of surface reactions, compared to about 4 per cent by volume of Earth’s mantle. Furthermore, neither primitive nor evolved hydrated Martian crust show noticeably different bulk densities compared to their anhydrous equivalents, in contrast to hydrous mafic terrestrial crust, which transforms to denser eclogite upon dehydration. This would have allowed efficient overplating and burial of early Martian crust in a stagnant-lid tectonic regime, in which the lithosphere comprised a single tectonic plate, with only the warmer, lower crust involved in mantle convection. This provided an important sink for hydrospheric water and a mechanism for oxidizing the Martian mantle. Conversely, relatively buoyant mafic crust and hotter geothermal gradients on Earth reduced the potential for upper-mantle hydration early in its geological history, leading to water being retained close to its surface, and thus creating conditions conducive for the evolution of complex multicellular life.
does serpentinization just refer to the formation of some hydrated minerals that happen to be of a class that is historically been referred to as serpentinite or it's subgroup
The following is multiple choice question (with options) to answer.
What form does water take on the planet mars? | [
"plasma",
"gas",
"liquid",
"ice"
] | D | Water on Mars can't be a liquid. This is because the pressure of the atmosphere is too low. The planet does have a lot of water; it is in the form of ice. The south pole of Mars has a very visible ice cap. Scientists also have evidence that there is also a lot of ice just under the Martian surface. The ice melts when volcanoes erupt. At this times liquid water flows across the surface. |
SciQ | SciQ-7437 | cell-biology, organelle
Title: Univocal identifying of a plant cell We yesterday got our biology-exams back and there's one exercise where I don't agree with my teacher. However, since he is the expert and not me, I need the support of external sources, i.e. experts in order to justify my statement.
Now in the exercise, we first had to identify the parts of a cell (which was shown in form of an image) and then in part b) reason whether it was an animal or plant cell.
I had identified a chloroplast and a vacuole and stated that the only cell with this organelles was the plant cell. My teacher answered that I had missed the fact, that the cell had also a cell wall (which is indeed a difference between plant and animal cells).
My question is
Is the fact that the cell had a cell wall necessary in my argumentation, i.e. are there other cells having chloroplasts and a vacuole without being a plant cell?
Could you provide a source which supports, or doesn't support my statement so that I can show it to my teacher?
Thanks in advance Your teacher is right, chloroplasts and vacuoles are not sufficient to define a plant cell.
Amoeba have both chloroplasts (McFadden et al, PNAS, 1994) and vacuoles (Day, J. Morphology, 1927) but they are not plants - and they do not have a cell wall.
Sea slugs eat algae and can "steal" their plastids and keep them working for weeks/months, effectively becoming photosynthetic animals for a while. This is called kleptoplastidy (Pillet, Mob. Genet. Elements, 2013).
The following is multiple choice question (with options) to answer.
The simplest system is that of contractile vacuoles present in what? | [
"macroorganisms",
"microorganisms",
"crystals",
"parasites"
] | B | 41.3 Excretion Systems Many systems have evolved for excreting wastes that are simpler than the kidney and urinary systems of vertebrate animals. The simplest system is that of contractile vacuoles present in microorganisms. Flame cells and nephridia in worms perform excretory functions and maintain osmotic balance. Some insects have evolved Malpighian tubules to excrete wastes and maintain osmotic balance. |
SciQ | SciQ-7438 | organic-chemistry, acid-base, esters, stereoelectronics
Extra: in a later article, Houk and Jorgensen11 revisited the topic to calculate the potential effects of solvation. A polar solvent would be expected to preferentially stabilise the more polar (E)-conformers 1 and 1a (which are more polar since the dipoles reinforce each other). It turns out that solvation in either water or acetonitrile only reduces $\Delta \Delta G$ by $\pu{1 kcal mol-1}$.
As for the stereoelectronic argument, only Alabugin7 offers any possible explanation:
The following is multiple choice question (with options) to answer.
Water's very polar compound causes most solutes to do what? | [
"combine",
"gel",
"repel",
"dissolve"
] | D | Many solutes dissolve in water because water is a very polar compound. |
SciQ | SciQ-7439 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
Which plant group has vascular tissue, seeds, and flowers? | [
"microbes",
"fungi",
"angiosperms",
"spores"
] | C | Angiosperms have vascular tissue, seeds, and flowers. |
SciQ | SciQ-7440 | optics, electromagnetic-radiation, visible-light, reflection
In this one, you can see how the mirror image "two to the right, one up" comes about. If you connect the source and this particular mirror image (dotted arrows), the line will pass through 3 different mirror planes (blue lines) in the mirrored domain. But this domain is just a mathematical auxiliary, the real light ray (solid arrows) only moves within the square described by the four mirrors. You can then see that the mirror images arises because of a certain repeated reflection on the mirrors, given by the somewhat rhombic shape of the solid arrows.
This construction using infinitely repeated mirror planes is in essence due to the law of specular reflection, that means that incident and reflected angles are the same. By that, you can either look at a reflected ray of light in an unchanged world or at an unchanged ray of light in a reflected world. This can be done each time your light ray hits a mirror, and you can describe your light ray as a line passing through different reflected worlds.
With this, you can also understand why mirror images with the same intensity lie on a diamond shape, $\diamond$. If you connect them to the origin, you pass through exactly the same number of mirrors in the reflected world for each one of them. Note that passing exactly through a corner means passing two mirror planes at once.
Each of the diamonds boundaries has $4 n$ points, where $n$ is the number of mirrors you have to pass to reach the cluster (you can just consider it the separation on the $x$ axis). That means that if the first $N$ diamonds are visible, you have a total of
$$\sum_{n=1}^N 4n = 4 \frac{N(N+1)}{2} = 2 N(N+1)$$
mirror images. That number obviously goes to infinity as $N \to \infty$.
The following is multiple choice question (with options) to answer.
The point in front of a mirror where the reflected rays intersect is known as what? | [
"focal point",
"periodic point",
"boundary point",
"reflective point"
] | A | Some mirrors have a curved rather than flat surface. Curved mirrors can be concave or convex. A concave mirror is shaped like the inside of a bowl. This type of mirror forms either real or virtual images, depending on where the object is placed relative to the focal point. The focal point is the point in front of the mirror where the reflected rays intersect. You can see how concave mirrors form images in Figure below and in the interactive animation at the URL below. The animation allows you to move an object to see how its position affects the image. Concave mirrors are used behind car headlights. They focus the light and make it brighter. They are also used in some telescopes. |
SciQ | SciQ-7441 | proteins, food, digestive-system, amino-acids, digestion
Title: How are proteins reused in the body? Part of what we eat are proteins,
and our body is in part build of proteins.
Are the proteins of the body build based on proteins in food at all?
Are proteins in food directly reused in the body,
or are proteins first disassembled?
How far are they disassembled, randomly in various pieces, or systematically to keep what can optimally be used to build new proteins, while nothing is wasted for energy?
(The question Can proteins/peptides pass through the intestine? and it's answers are related, and provide some context and relevant parts, but is not a duplicate.) Short answer: Indeed the proteins in our body are based on amino acids from external food sources. BUT, proteins up-taken from food are ALWAYS disassembled first into amino acids, through specialized enzymes, proteases, (for instance Pepsin in the stomach's gastric juices and Tripsin in the pancreatic juices), during digestion, in the alimentary canal, (gut). This enables the body's liver to build the proteins most needed by the organism itself, through the processes of transamination, that allows conversion betwixt amino acids, and deamination, that removes N2 from the amino acid, (let's say the "amino" part is removed, and then expelled as urea), to excrete amino acids in excess. In addition this breaking down of external proteins is necessary, since they can act as labels for pathogens, and external organisms in general, and thus would soon be destroyed by the immune system if reused straight away.
The following is multiple choice question (with options) to answer.
Any unused energy in food, whether it comes from carbohydrates, proteins, or lipids, is stored in the body where? | [
"fat",
"kidneys",
"spleen",
"bones"
] | A | Any unused energy in food, whether it comes from carbohydrates, proteins, or lipids, is stored in the body as fat. An extra 3,500 Calories of energy results in the storage of almost half a kilogram (1 pound) of stored body fat. People who consistently consume more food energy then they need may become obese. Obesity occurs when the body mass index is 30.0 kg/m 2 or greater. Body mass index (BMI) is an estimate of the fat content of the body. It is calculated by dividing a person’s weight (in kilograms) by the square of the person’s height (in meters). Obesity increases the risk of health problems such as type 2 diabetes and hypertension. |
SciQ | SciQ-7442 | aqueous-solution, solubility, solutions, precipitation
s &= \sqrt{4 \times 10^{-10}}\\
s &= 2 \times 10^{-5}
\end{align}
Now, when the solids is mixed in water, There should be $[\ce{SO4^2-}] =3 \times 10^{-5.5} $ and $[\ce{S2O3^2-}] =2 \times 10^{-5} $.
Now I confuse what ion concentration should I use to determine $[\ce{Ba^2+}]$
EDIT 2:
\begin{align}
K_\mathrm{sp}(\ce{BaSO4}) &= [\ce{Ba^2+}] \times [\ce{SO4^2-}] \\
\frac{K_\mathrm{sp}(\ce{BaSO4})}{[\ce{Ba^2+}]} &= [\ce{SO4^2-}] \\
\end{align}
and
\begin{align}
K_\mathrm{sp}(\ce{BaS2O3}) &= [\ce{Ba^2+}] \times [\ce{S2O3^2-}] \\
\frac{K_\mathrm{sp}(\ce{BaS2O3})}{[\ce{Ba^2+}]} &= [\ce{S2O3^2-}] \\
\end{align}
From @santimirandarp answer, I got that :
\begin{align}
[\ce{Ba^2+}] &= [\ce{S2O3^2-}] + [\ce{SO4^2-}]\\
[\ce{Ba^2+}] &= \frac{K_\mathrm{sp}(\ce{BaS2O3})}{[\ce{Ba^2+}]} + \frac{K_\mathrm{sp}(\ce{BaSO4})}{[\ce{Ba^2+}]}\\
The following is multiple choice question (with options) to answer.
What helps determine the concentration of a species in a solution? | [
"qualitative analysis",
"quantitative analysis",
"technical analysis",
"fundamental analysis"
] | B | Summary The concentration of a species in solution can be determined by quantitative analysis. One such method is a titration, in which a measured volume of a solution of one substance, the titrant, is added to a solution of another substance to determine its concentration. The equivalence point in a titration is the point at which exactly enough reactant has been added for the reaction to go to completion. A standard solution, a solution whose concentration is known precisely, is used to determine the concentration of the titrant. Many titrations, especially those that involve acid–base reactions, rely on an indicator. The point at which a color change is observed is the endpoint, which is close to the equivalence point if the indicator is chosen properly. |
SciQ | SciQ-7443 | evolution, natural-selection, population-dynamics, adaptation
Title: Genetic Diversity and Adaptation I am somewhat new to evolutionary biology, having studied it on my free time as a computer science student. There is one particular thing that has always bothered me for which I have not seen a good treatment, relating to adaptations to the environment with respect to genetic diversity. If it is possible for a population to adapt to rapid environmental changes, and they don't have an adaptation for dealing with change directly (such as a complex brain), it seems to me that every generation must have present within them almost every possible environmental adaptation that the population is capable of expressing (including many irrelevant ones and a few relevant to the particular environmental challenge). Otherwise, it may take too many generations to deal with a change, which may be disastrous for the population.
So my question would be: how does an evolutionary biologist explain the mechanics behind the ability for a population to adapt quickly? Are most environmental changes slow or gradual enough that the population has a few generations to happen upon the mutations that will allow it to survive, and have generally been successful in this regard for 3.5 billion years? Or, are a large majority of possible adaptations present in almost every generation, and just serve no purpose or advantage for most of the population if the provided "benefit" is unneeded (i.e., are effectively neutral)? Or something in between? It is a good question. The question is hard to answer though because
The answer is not completely resolved
There are many influential parameters hidden behind this question.
Your question, as I understand it, can be formulated as
Do natural populations have enough genetic variance to directly respond to an environmental change or do they have to wait for this variance to be created through mutations?
To address this question, I will have to assume you have some intermediate level of knowledge in evolutionary biology.
How do we call these two alternatives?
Adaptation can occur through selection on:
Standing genetic variance
De novo mutations
How can we tell them apart?
This section is mainly inspired from Barrett and Schluter (2008).
Adaptation from standing genetic variance and from de novo mutations tend to yield different genetic signature.
In comparison to de novo mutations, adaptation from standing genetic variation is likely to lead to
Faster evolution
Because there the respond to the new environmental is immediate, there is no need to wait for more mutations.
Because the fitness variance associated with the trait under selection is very low even when the first mutation occurs.
Fixation of more alleles of small effects.
The following is multiple choice question (with options) to answer.
In order to survive and maintain what state, an organism must quickly adapt to changing environmental conditions? | [
"regulation",
"homeostasis",
"ketosis",
"acclimatization"
] | B | In prokaryotes, a combination of activators and repressors determines whether a gene is transcribed. As you know, prokaryotic organisms are fairly simple organisms with much less DNA. Prokaryotic genes are arranged in operons , a region of DNA with a promoter, an operator , and one or more genes that encode proteins needed to perform a certain task. To maintain homeostasis (and survive), the organism must quickly adapt changing environmental conditions. The regulation of transcription plays a key role in this process. |
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