source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-1344 | cell-biology, bioinformatics
Title: Would there be more amino acid residues in the extracellular or intercellular space? I am working on a bioinformatics project with HMMs and want to write some initiation probabilities for the location of amino acid residues. I know for different transmembrane proteins there will be different cases, but, in general, which regions of the protein would correspond to more AA residues: intracellular or extracellular? Or is there no general pattern? Yes ,there are some patterns.
First you have to determine which group of membrane proteins you're talking about.
According to Molecular Cell Biology Lodish et al 8th ed chapter 13, there are 6 types of ER membrane proteins ( and therefore in the cell membrane)
The 6 types are type 1,type 2 ,type 3 , type 4,Tail anchored proteins ,GPI anchored proteins.
Nearly all AA residues in type 3 or the tail-anchored type are located in the cytosolic side of the membrane ( their difference is in their N/C terminus orientation) whereas GPI anchored type has almost its entire AA residues in the exoplasmic side.
For other types there may not be a general pattern.
See E. Hartmann et al., 1989, P. Natl. Acad. Sci. USA
86:5786, and C. A. Brown and S. D. Black, 1989, J. Biol. Chem. 264:4442.
By the way , you can also think of it in another way. Antigens , Hormone Receptors , Structral proteins in exoplasmic leaflet of membrane usually have more AA in the exoplasmic side.
The following is multiple choice question (with options) to answer.
Where are integral proteins embedded? | [
"hemoglobin",
"mitochondria",
"cytoplasm",
"libid bilayer"
] | D | |
SciQ | SciQ-1345 | biochemistry
Specific Force Deficit in Skeletal Muscles of Old Rats Is Partially
Explained by the Existence of Denervated Muscle Fibers
Association of adiponectin and resistin with adipose tissue
compartments, insulin resistance and dyslipidaemia
Shifts in the Distribution of Mass Densities Is a Signature of
Caloric Restriction in Caenorhabditis elegans
The following is multiple choice question (with options) to answer.
Skeletal muscles are attached to bones by what? | [
"tendons",
"plasma",
"veins",
"enzymes"
] | A | Skeletal muscles are attached to bones by tendons. |
SciQ | SciQ-1346 | human-anatomy
Title: Difference between Appendix and the Cecum? What's the difference between an appendix and a cecum, and what are their functions? In herbivores the Cecum is an area that stores plant matter and helps digest it via symbiotic bacteria. Carnivores have smaller Cecums because meat is easier to digest than plant matter. In humans the Cecum is also an anatomical landmark that delineates the change from small intestine (a digesting organ) to the large intestine (mostly a capacity/storage organ).
The Appendix is a small, previously thought "superfluous" fleshy worm-shaped organ at the junction between the small and large intestines. Recent research posits that the appendix is sort of a harbor for a person's gut flora that can re-populate the intestines should the existing bacteria die or get removed (diarrhea being the most common cause). It can also become infected, inflamed, and require surgery to remove (Appendicitis).
The following is multiple choice question (with options) to answer.
The duodenum, the jejunum, and the ileum are the main regions of which organ? | [
"heart",
"small intestine",
"lungs",
"large intestine"
] | B | 23.5 The Small and Large Intestines The three main regions of the small intestine are the duodenum, the jejunum, and the ileum. The small intestine is where digestion is completed and virtually all absorption occurs. These two activities are facilitated by structural adaptations that increase the mucosal surface area by 600-fold, including circular folds, villi, and microvilli. There are around 200 million microvilli per square millimeter of small intestine, which contain brush border enzymes that complete the digestion of carbohydrates and proteins. Combined with pancreatic juice, intestinal juice provides the liquid medium needed to further digest and absorb substances from chyme. The small intestine is also the site of unique mechanical digestive movements. Segmentation moves the chyme back and forth, increasing mixing and opportunities for absorption. Migrating motility complexes propel the residual chyme toward the large intestine. The main regions of the large intestine are the cecum, the colon, and the rectum. The large intestine absorbs water and forms feces, and is responsible for defecation. Bacterial flora break down additional carbohydrate residue, and synthesize certain vitamins. The mucosa of the large intestinal wall is generously endowed with goblet cells, which secrete mucus that eases the passage of feces. The entry of feces into the rectum activates the defecation reflex. |
SciQ | SciQ-1347 | thermodynamics, pressure, temperature
Title: Relations between pressure and temperature I have several questions concerning thermodynamics and I order them in 4 points that may be related:
What's the difference between heat and work at the atomic level? Isn't heat simply work between particles colliding with different momentum against each other?
Consider a chamber containing a gas. Does an increase of pressure also increases the temperature of the gas? Is that a result of the mechanical action that puts the piston to move delivering energy to the gas through work?
But if one is able to displace the piston a little bit so that during this process no collision happens there will be no energy delivered, and the temperature doesn't rise. Is that possible?
Excluding water and other special materials, why does a increase of pressure over a solid rises is melting point?
My teacher said that pressure would decrease the molecules motion, so in order to melt the solid we should give more energy through heat. Is this correct? If yes, then see the link referred on the $4^{th}$ point (the document says that pressure rises temperature)
The inner core of the Earth is solid but is also at higher temperatures than the liquid outer core. I did some research and is often stated that pressure is the reason why the inner core is solid. But returning to the $3^{rd}$ point, if the pressure reduces the motion of the particles, how can the inner core have material with higher temperatures (i.e. particles with higher average kinetic energy)?
In this link the article states that pressure over the material inside earth increases the temperature. However if the pressure doesn't reduce the particles motion, then how can particles that jiggle so much be in the solid state? I'll give brief answers to your questions. If you need more detail, you should ask your questions separately.
What's the difference between heat and work at the atomic level? Isn't heat simply work between particles colliding with different momentum against each other?
The following is multiple choice question (with options) to answer.
Temperature and pressure affect changes in phases or states of what? | [
"homeostasis",
"matter",
"energy",
"decay"
] | B | Most substances have three distinct phases: gas, liquid, and solid. Phase changes among the various phases of matter depend on temperature and pressure. The existence of the three phases with respect to pressure and temperature can be described in a phase diagram. Two phases coexist (i. , they are in thermal equilibrium) at a set of pressures and temperatures. These are described as a line on a phase diagram. The three phases coexist at a single pressure and temperature. This is known as the triple point and is described by a single point on a phase diagram. A gas at a temperature below its boiling point is called a vapor. Vapor pressure is the pressure at which a gas coexists with its solid or liquid phase. Partial pressure is the pressure a gas would create if it existed alone. Dalton’s law states that the total pressure is the sum of the partial pressures of all of the gases present. |
SciQ | SciQ-1348 | everyday-life, water, physical-chemistry, surface-tension
Title: Why do hot water droplets persist in cooler water? I notice this phenomenon typically when mixing hot or warm water with cold water. Basically, tiny droplets of hot water travel inside the body of cooler water and persist. I have included a photo of when I noticed this happening (in a bathtub with hot water coming out of a showerhead) and those little white spheres are what I'm asking about. I can also provide a short video if it would be helpful.
Specifically, the conditions to generate these droplets are as follows:
Take a US consumer detachable (<2.5 gallon per minute flow rate) shower-head with hot water (near the temperature of my home's hot water heater which is a typical US residential gas-powered water heater with a standard temperature set-point), and angle the water towards the far end of the bathtub. This shower-head has different nozzle settings and the one that I have chosen produces a fine mist of droplets similar to that produced when using a typical plastic spray bottle. This is not a uniform effect as the water is emitted from nozzles that are placed in an annulus. I have noticed that from this shower-head, water is emitted as a cone; droplets and partial streams in the middle of the cone are much hotter than those on the outside of the cone. This middle stream of water is maybe 50-60 degrees Celsius, which I estimate because I can touch the water stream for ~3 seconds before feeling it is too hot. The outer water cone is warm to the touch, so presumably it is between 36 degrees and 45 degrees Celsius.
I believe the majority of the water (especially that on the outside), through a combination of evaporative cooling and conductive cooling (due to the fiberglass body of the bathtub) forms a lower temperature body of water. Some droplets, however, retain a much higher temperature (as the shower-head is not able to produce a completely uniform droplet spray) and join the body of water. For some reason, these water droplets do not coalesce with the cooler body of water.
Is there a name for this phenomenon, and a description for the conditions to reproduce it?
I understand there are complaints about image quality. I cannot fix these as I do not have access to photography equipment to take higher quality images. (This photo was taken with a flagship 2023 smartphone).
The following is multiple choice question (with options) to answer.
The water in some springs are hot because they're heated by what? | [
"gravity",
"the sun",
"fires",
"hot magma"
] | D | Some springs have water that contains minerals. Groundwater dissolves minerals out of the rock as it seeps through the pores. The water in some springs is hot because it is heated by hot magma. Many hot springs are also mineral springs. That’s because hot water can dissolve more minerals than cold water. |
SciQ | SciQ-1349 | species-identification
Title: What is this (water-loving) bug? For some time we've been finding these little fellows in our apartment:
They seem harmless enough, but finding them is a bit... annoying. I found the fellow above in the bathtub, and it's not uncommon to find more than one.
Unfortunately, some started to appear near the kitchen sink as well. Or outside of the bathroom on the floor (at least that's where we noticed them).
I think this thing prefers darkness over light, and seems to be drawn towards wet places or just water. These critters are also surprisingly fast.
What is it? Should we be concerned about a pest problem, or is this just a minor, unwelcome guest?
PS. We live in Poland. It is a Lepisma saccharina or silverfish.
It is rather common and yes, it's harmless.
The following is multiple choice question (with options) to answer.
What consists of all the living things and nonliving things interacting in the same area? | [
"habitat",
"ecosystem",
"biome",
"biodiversity"
] | B | An ecosystem consists of all the living things and nonliving things interacting in the same area. |
SciQ | SciQ-1350 | human-biology, microbiology
Title: How much weight/volume do microbes occupy within the human body? Microorganisms constitute the bulk of all the biomass on Earth. I weighed myself yesterday, and wondered how much less I would weigh if I were completely free of bacteria and microbes, inside and out.
Approximately how much weight and volume do microbes occupy within the average human body? How were these values obtained? @AlanBoyd's calculations are reasonable, I think the estimate is off though. The human microbome includes other bacteria which are not necessarily E.coli equivalent.
The human microbome projects give estimates that microbes are 1-3% total body mass. i.e. several pounds of bacteria.
The GI tract alone has most of the microbome mass - faeces is ~60% intestinal flora/fauna by dry weight, which for many adults alone must be hundreds of grams at any given moment.
The following is multiple choice question (with options) to answer.
How much can the bacteria in your gut weigh? | [
"2 kilograms",
"2 pounds",
"2.2 pounds",
"2.15 pounds"
] | B | Lastly, keep in mind the small size of bacteria. Together, all the bacteria in your gut may weight just about 2 pounds. |
SciQ | SciQ-1351 | biochemistry, physiology, muscles, bioenergetics
Title: Location of t tubule in muscle Why do mammalian skeletal muscles have t-tubules at the junction of the anisotropic and isotropic band, whereas non-mammalian muscles and cardiac muscles have it at Z-line? What could have been the functional significance?
If skeletal muscle would have it at the Z-line then I think it would have been more effective in contraction of muscle fibre. So which arrangement is more efficient?
Also, why is a common arrangement (the more efficient one) not seen in all those muscle types? Interesting question. Indeed it is related to the working of cardiac muscles. First of all, lets have a look at the structure of a sarcomere of a cardiac muscle from here:
Here, what we can see is that the t-tubule is a depression formed in myocyte. It is important to know this fact here. Why? See this:
In contrast to skeletal muscle, cardiac muscle requires extracellular calcium ions for contraction to occur. Like skeletal muscle, the initiation and upshoot of the action potential in ventricular cardiomyocytes is derived from the entry of sodium ions across the sarcolemma in a regenerative process. However, an inward flux of extracellular calcium ions through L-type calcium channels sustains the depolarization of cardiac muscle cells for a longer duration. The reason for the calcium dependence is due to the mechanism of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum that must occur during normal excitation-contraction (EC) coupling to cause contraction.
First, cardiac muscles don't work by external action potentials, they work on a cycle governed by themselves, known as the cardiac cell cycle.
Second, as is clear from above paragraph, these cells depend on extracellular Ca2+ ions for initiating contraction, a clear difference from skeletal muscles which need Ca2+ stored in SR. Hence, they require t-tubule at a place where a sarcomere ends. Obviously, having a depression in the middle of a sarcomere (i.e. between I- and A-band) would not work here.
Also, the structure of t-tubules is also different between the two. Compare my first image with the image below from here:
The following is multiple choice question (with options) to answer.
As a myotube is formed from many different myoblast cells, it contains many nuclei, but has a continuous what? | [
"cytoplasm",
"cerebellum",
"nucleus",
"mucus"
] | A | or myotube. As a myotube is formed from many different myoblast cells, it contains many nuclei, but has a continuous cytoplasm. This is why skeletal muscle cells are multinucleate, as the nucleus of each contributing myoblast remains intact in the mature skeletal muscle cell. However, cardiac and smooth muscle cells are not multinucleate because the myoblasts that form their cells do not fuse. Gap junctions develop in the cardiac and single-unit smooth muscle in the early stages of development. In skeletal muscles, ACh receptors are initially present along most of the surface of the myoblasts, but spinal nerve innervation causes the release of growth factors that stimulate the formation of motor end-plates and NMJs. As neurons become active, electrical signals that are sent through the muscle influence the distribution of slow and fast fibers in the muscle. Although the number of muscle cells is set during development, satellite cells help to repair skeletal muscle cells. A satellite cell is similar to a myoblast because it is a type of stem cell; however, satellite cells are incorporated into muscle cells and facilitate the protein synthesis required for repair and growth. These cells are located outside the sarcolemma and are stimulated to grow and fuse with muscle cells by growth factors that are released by muscle fibers under certain forms of stress. Satellite cells can regenerate muscle fibers to a very limited extent, but they primarily help to repair damage in living cells. If a cell is damaged to a greater extent than can be repaired by satellite cells, the muscle fibers are replaced by scar tissue in a process called fibrosis. Because scar tissue cannot contract, muscle that has sustained significant damage loses strength and cannot produce the same amount of power or endurance as it could before being damaged. Smooth muscle tissue can regenerate from a type of stem cell called a pericyte, which is found in some small blood vessels. Pericytes allow smooth muscle cells to regenerate and repair much more readily than skeletal and cardiac muscle tissue. Similar to skeletal muscle tissue, cardiac muscle does not regenerate to a great extent. Dead cardiac muscle tissue is replaced by scar tissue, which cannot contract. As scar tissue accumulates, the heart loses its ability to pump because of the loss of contractile power. However, some minor regeneration may occur due to stem cells found in the blood that occasionally enter cardiac tissue. |
SciQ | SciQ-1352 | thermodynamics, gas-laws, ideal-gas
Title: How can I calculate the density of a gas mixture using the ideal gas? I am trying to calculate the density of the ideal gas mixture given the following data:
The gases are helium and oxygen. There are $\pu{8 g}$ $\ce{He}$ and $\pu{16 g}$ $\ce{O2}$. The temperature is $\ce{300 K}$. The pressure is $\pu{100 kN m-2}$.
So I know density is mass per volume, but I don't know where to get the volume from. I thought I would get it from the Ideal Gas law, but I can find $p\cdot V$ for both gases after finding the quantity for both gases, but I don't know where to go from there. I only know that the pressures add up to $\pu{100 kN m-2}$. Your sample is made of $2$ moles $\ce{He}$ + $0.5$ mol $\ce{O2}$. So the total gas amount is $n = 2.5$ moles. Its total mass is $m = \pu{ 2 mol · 4 g/mol + 0.5 mol · 32 g/mol = 24 g}$ Now the volume of $2.5$ mole ideal gas can be calculated from : $V = nRT/p$, with $p = 10^5$ Pa, and $T = 300$ K. Divide $24 $ g by this volume, and you get the answer. Go ! Do the calculation yourself !
The following is multiple choice question (with options) to answer.
When thinking of the rate at which two gases mix, it is inverse proportional to the density of what? | [
"the container",
"matter",
"gas",
"dioxide"
] | C | The rate at which two gases mix. Inversely proportional to the density of the gas. |
SciQ | SciQ-1353 | human-biology, virology, pathology
Title: Why is rabies incurable? I'm still not sure about the mechanics that lead to rabies being incurable. I know that it can be treated before any symptoms show up, but why is it that once symptoms show the person is a dead man walking? This is because rabies is a viral infection of nervous tissue that propagates through peripheral nerves into the brain and causes brain tissue inflammation (encephalitis).
As long as the virus is in the brain there is no way to get rid of it. The main trade-off here is that everything that would kill the virus will be as (or even more) aggressive against the brain tissue, and impairment of the latter will lead to really heavy deficits in vital functions like breathing and thermoregulation.
The first manifestations of rabies are those due to brain damage. This means, the virus is already there and the brain is already fatally damaged.
The following is multiple choice question (with options) to answer.
What serious sti can damage the heart, brain and other organs or even cause death, if untreated? | [
"syphilis",
"chlamydia",
"herpes",
"cirrhosis"
] | A | Syphilis is a very serious STI. Luckily, it is less common than chlamydia or gonorrhea. Syphilis usually begins with a small sore on the genitals. This is followed a few months later by a rash and flu-like symptoms. If syphilis is not treated, it may damage the heart, brain, and other organs. It can even cause death. |
SciQ | SciQ-1354 | genetics, botany, seeds
Title: What DNA does a self-fertile plant's seedling have? Some plants are said to be self-fertile. An example is Prunus tomentosa.
Assuming that no cross-pollination happened with other plants, if a self-fertile plant such as prunus tomentosa produces a seedling, what DNA will the seedling have? Is the seedling's DNA an exact copy of the parent plant's DNA, or do the genes get rearranged? Selfing (aka self-fertilizing) differs from cloning. When selfing occurs, the offspring is not an exact copy of the parent. When cloning occurs, the offspring is an exact copy (except for a few mutations) of the parent.
Selfing implies that an individual will produce two gametes (typically a spermatozoid and an ovule but that might be a bit more complicated) and these two gametes are fusing to give the zygote (egg or offspring if you prefer).
As a consequence, when selfing, meiosis is occurring (and therefore segregation and recombination) so that the offspring is not an exact clone of the parent but rather some kind of a rearrangement of the parent genome (with a few mutations of course).
The following is multiple choice question (with options) to answer.
When a seed is produced by apomixis, the embryo develops without what? | [
"infection",
"infection",
"stimulation",
"fertilization"
] | D | |
SciQ | SciQ-1355 | electrochemistry, oxidation-state
Title: Determine if the following change is an oxidation, a reduction, or neither
The following reaction is not a complete reaction. Determine if the change is an oxidation, a reduction, or neither:
$$\ce{CrO4^{-2} -> Cr2O7^{-2}}$$
I know that the answer to this problem is neither, but I don't have any idea as to how that answer is reached. Could anyone give me a hint? I am familiar with oxidation, reduction, and oxidation numbers. Find the oxidation numbers of the substances in each compound.
You should find the oxidation number of Cr in each compound to be +6, and the oxidation number of O to be -2. Since there is no change in the oxidation numbers, this reaction is neither an oxidation or reduction.
The following is multiple choice question (with options) to answer.
When an oxidation number of an atom is decreased in the course of a redox reaction, that atom is being what? | [
"increased",
"destroyed",
"reduced",
"replaced"
] | C | All redox reactions occur with a simultaneous change in the oxidation numbers of some atoms. At least two elements must change their oxidation numbers. When an oxidation number of an atom is increased in the course of a redox reaction, that atom is being oxidized. When an oxidation number of an atom is decreased in the course of a redox reaction, that atom is being reduced. Thus oxidation and reduction can also be defined in terms of increasing or decreasing oxidation numbers, respectively. Saylor URL: http://www. saylor. org/books. |
SciQ | SciQ-1356 | blood-circulation
Title: Why don't we bleed interstitial fluid? Interstitial fluid is the fluid between cells in tissues - forming the medium between cells and capillaries. From what I gather, the typical human has 5L of blood and 11L of interstitial fluid. This raises an interesting question. If I get cut, why do I not bleed interstitial fluid?
When humans are cut, generally their capillaries open and blood comes out. But this should also allow the interstitial fluid to come out - so why don't we see it? For fluid to flow from a wound there needs to be a significant pressure gradient between where it is now and the outside of the body. Your skin generally does not have a strong compressive effect, which is why a deep cut exposing fat will not lead to the fatty tissue being expulsed from the body any more than the interstitial fluid is.
Blood, however, flows. For it to circulate there needs to be a pressure gradient between where it is now and where it is going. Since veins (including the vena cava, which channels blood back into the heart) do not have vascular walls strong enough to create a suction effect (i.e. lower pressure than the surrounding tissue), you can conclude that the pressure of blood vessels is always higher than that of surrounding tissues, and thus higher than the pressure outside of your body. This is why all blood vessels, including veins, will bleed, whereas less pressurized systems such as interstitial fluid will not.
The following is multiple choice question (with options) to answer.
A venule is an extremely small vein, generally 8–100 micrometers in diameter. postcapillary venules join multiple capillaries exiting from a capillary bed. multiple venules join to form what? | [
"clots",
"veins",
"arteries",
"glands"
] | B | Venules A venule is an extremely small vein, generally 8–100 micrometers in diameter. Postcapillary venules join multiple capillaries exiting from a capillary bed. Multiple venules join to form veins. The walls of venules consist of endothelium, a thin middle layer with a few muscle cells and elastic fibers, plus an outer layer of connective tissue fibers that constitute a very thin tunica externa (Figure 20.7). Venules as well as capillaries are the primary sites of emigration or diapedesis, in which the white blood cells adhere to the endothelial lining of the vessels and then squeeze through adjacent cells to enter the tissue fluid. |
SciQ | SciQ-1357 | javascript, jquery
}
},
traps:{
//sample object
}
};
$('#tree div').bind("contextmenu", function (e) {
e.preventDefault();
});
$('#tree .tab div').mousedown(function (e) {
var $this = $(this);
$this.attr('unselectable', 'on').css('UserSelect', 'none').css('MozUserSelect', 'none');
var $tab = $this.parent().attr("id");
var $skill = $this.attr("id");
function checkPreReq(e) {
var $preReq = skill[$tab][e]['preReq'];
var $preReq2 = skill[$tab][e]['preReq2'];
alert($preReq);
if ($preReq === false) {
alert('no pre-req');
return true;
} else if ($preReq !== false) {
alert('pre-req1 exists');
if(skill[$tab][$preReq]['base'] > 0) {
alert('pre-req1 higher than 0');
if ($preReq2 === undefined) {
alert('no second pre-req, go on');
return true;
} else {
alert('check second pre-req value');
if (skill[$tab][$preReq2]['base'] > 0) {
alert('pre-req2 higher than 0');
return true;
} else {
alert('pre-req2 not met (0)');
return false;
}
}
} else {
alert('pre-req1 not met (0)');
return false;
}
} else {
alert('else');
return false
}
}
if (e.which == 1) {
//leftclick
The following is multiple choice question (with options) to answer.
The active site can only bind certain what? | [
"membranes",
"substrates",
"electrons",
"proteins"
] | B | The active site is specific for the reactants of the biochemical reaction the enzyme catalyzes. Similar to puzzle pieces fitting together, the active site can only bind certain substrates. |
SciQ | SciQ-1358 | zoology
Capybara, rabbits, hamsters and other related species do not have a complex ruminant digestive system. Instead they extract more nutrition from grass by giving their food a second pass through the gut. Soft fecal pellets of partially digested food are excreted and generally consumed immediately. Consuming these cecotropes is important for adequate nutritional intake of Vitamin B12. They also produce normal droppings, which are not eaten.
Young elephants, pandas, koalas, and hippos eat the feces of their mother to obtain the bacteria required to properly digest vegetation found on the savanna and in the jungle. When they are born, their intestines do not contain these bacteria (they are completely sterile). Without them, they would be unable to obtain any nutritional value from plants.
Eating garbage and human feces is thought to be one function of dogs during their early domestication, some 12,000 to 15,000 years ago. They served as our first waste management workers, helping to keep the areas around human settlements clean. A study of village dogs in Zimbabwe revealed that feces made up about 25% of the dogs’ overall diet, with human feces making up a large part of that percentage.
Coprophagia
Daily rhythms of food intake and feces reingestion in the degu, an herbivorous Chilean rodent: optimizing digestion through coprophagy
Coprophagia as seen in Thoroughbred Foals
The following is multiple choice question (with options) to answer.
In a food chain, what group of organisms breaks down animal remains and wastes to get energy? | [
"detritivores",
"decomposers",
"primary consumers",
"producers"
] | B | Decomposers break down animal remains and wastes to get energy. |
SciQ | SciQ-1359 | ichthyology, homeostasis, osmoregulation
Pillans, R.D. and C.E. Franklin, 2004. Plasma osmolyte concentrations and rectal gland mass of bull sharks Carcharhinus leucas, captured along a salinity gradient. Comparative Biochemistry and Physiology, Part A 138: 363-371.
The following is multiple choice question (with options) to answer.
What is the term for organisms that have adaptations to both salty and basic conditions? | [
"heterophiles",
"salinophytes",
"haloalkaliphiles",
"sporozoans"
] | C | Alkaliphiles are organisms that "love" bases. Bases are like the opposite of acids. Basic environments where archaeans are found include Mono Lake in California, pictured in Figure below . Mono Lake is the oldest lake in North America. The water is not only unusually basic. It's also saltier than the ocean. So archaeans that live in the water of Mono Lake must have adaptations to both salty and basic conditions. They are haloalkaliphiles. |
SciQ | SciQ-1360 | ecology
Title: Do invasive species cause long-term damage to ecosystems they invade? Growing up in the U.S., I was warned at various times of the dire consequences of a variety of introduced pests (usually insects).
Japanese beetles, gypsy moths, and most recently the brown marmorated stink bug are all introduced pests that, at various times, were described as serious threats to our ecology.
These threats aren't confined to arthropods, either. The giant African land snail is causing a stir in Florida (indeed, Florida seems to suffer from an excessive variety of introduced species.
"Lack of native predators" is frequently cited as the primary reason many invasive species are considered such a risk to the ecology.
I understand that these introduced species can place tremendous pressure on native species that fill similar ecological niches, and may even push these species out of the region due to competition for food and habitat. However, do the overall ecologies that these species are introduced to adjust over long periods of time?
The numbers of Japanese beetles and gypsy moths don't seem anywhere as high as when I was a child. Has the ecosystem adjusted, or has the overpopulation self-corrected as the species ran low on food through over-consumption? Or are the populations still just as problematic now as they were 30 years ago, and I just am not seeing the bigger picture?
What is the long-term impact that we've seen from invasive, introduced species? Is there a significant difference on the long-term impact between introduced flora, arthropods, or mammals? The answer really depends on how you think of invasive. One extreme answer is to say that all things are relative, and that the concepts of local and invasive are all relative. This matters to a certain extent because ecologists draw a fuzzy line between invasive and naturalized. You could start with some basic species that we all think of as either good, local, or neutral. Take the earthworm. Most people think of it as a common native species, but the earthworm is actually an invasive species that has radically changed much of North America that came over with the Europeans. Similarly, brown trout are also invasive, coming to the US in the 1800's.
The following is multiple choice question (with options) to answer.
What organism is the most disruptive towards the diversity of other species? | [
"reptiles",
"bacteria",
"insects",
"humans"
] | D | |
SciQ | SciQ-1361 | physiology, homework
Title: Order of events in hibernation
Arrange this in sequence :
i. Heat loss exceeds heat production.
ii.As body temperature falls, heat loss decreases.
iii.Body temperature equals environmental temperature.
iv.Metabolic activities fall to the basal level.
I am confused between i,iii,ii,iv and iv,i,ii,iii. I think the order i,ii,iii should be correct, since the fall in temperature occurs after the heat loss exceeds production and will continue only till the temperature equals the ambient temperature. iv is the reason for i. Hence iv,i,ii,iii sounds pretty convincing to me.
With i,iii,ii,iv , the main problem is that there can not be any appreciable fall in temperature ii after the temperature equals the environmental temperature iii. And iv seems more probably to be the reason for i rather than the reverse
The following is multiple choice question (with options) to answer.
Migration and hibernation are examples of behaviors that occur on what temporal basis? | [
"daily",
"weekly",
"nocturnal",
"annual"
] | D | Many animal behaviors occur in repeated cycles. Migration and hibernation are examples of behaviors with annual cycles. Sleeping and waking are examples of behaviors with daily cycles. |
SciQ | SciQ-1362 | botany, microbiology, terminology, etymology
Title: Rhizosphere vs. Endorhiza? In relation to microbiology and the naming of the various areas of the plant as it relates to microbial inhabitance, I am confused as to the difference between the terms endorhiza and rhizosphere.
In this case I see rhizosphere referred simply to as the 'roots', but in this case I also see endorhiza explained simply as 'roots' also.
However in this case, I see a further explanation for endorhiza (which does make sense etymologically): 'internal root tissues'.
Does this mean endorhiza is be a sub-term for the area inside the roots, and the larger area of the rhizome in general represented by rhizosphere, and that is the difference? Healthy plant growth depends on a microbial community that lives around and inside the roots of plants (Bais et al. 2001). Roots secrete from the roots a number of chemical compounds that influences the microbial community around but outside of the roots. The microbial community can include bacteria, fungi, and single-celled parasites, as well as larger organisms like insect larvae and even roots from other plants. Some chemicals attract certain organisms while other chemicals repel organisms. This community of organisms around the roots is called the rhizosphere (Walker et al. 2003). The paper by Walker (open access) describes some of the many types of symbiotic relationships that occur in the rhizosphere.
Endorhiza refers to the internal environment of the root system. The endorhiza contains another microbial community of bacteria and fungi (Backman and Sikora 2008). The organisms of this endorhizal community are collectively called endophytes. Like the rhizosphere, the organisms in the endorhiza are important symbiotic species that benefit the health of the plant.
Similar communities have been identified for other regions of the plant, such as the phyllosphere, the organisms that live on the leaves, stems and other plant parts above the ground (Backman and Sikora 2008).
The following is multiple choice question (with options) to answer.
What are all of the living or once-living aspects of the environment called? | [
"biotic factors",
"photic factors",
"fossils",
"abiotic factors"
] | A | Biotic factors are all of the living or once-living aspects of the environment. They include all the organisms that live there as well as the remains of dead organisms. |
SciQ | SciQ-1363 | neuroscience, brain
When $m$ synapses simultaneously generate an EPSP of size $u$, these EPSPs will sum up at the axon hillock to
$$ U = m\times u\times 10^{-\alpha r}$$
Only if $U \geq \theta$ an action potential will be generated, that is, the minimal number of simultaneously active synapses to generate an action potential is
$$ n = 10^{\alpha r}\ \frac{\theta}{u}$$
With this we can estimate the excitability $E = \log\frac{N}{n} = \log 10^{-\alpha r}\frac{N\ u}{\theta}$ by
$$E = -\alpha r + \log(N) + \log \frac{u}{\theta} $$
$\alpha$, $u$ and $\theta$ are more physical constants (more or less the same for all types of neurons?), $r$ and $N$ depend heavily on the arbitrary geometry/morphology of the neuron (especially do longer and more strongly branched dendrites have more synapses).
My specific questions are (please feel free to answer only with "yes" or "no"):
Has the property of excitability (in the operational sense above) been investigated a) for single neurons, b) for morphological types of
neurons?
Is there an observed significant correlation between morphological type and excitability? Note that larger dendritic trees have larger
$r$ (decreasing $E$) but also larger $N$ (increasing $E$).
The following is multiple choice question (with options) to answer.
Temporal and spatial summation at the axon hillock determines whether a neuron generates what? | [
"change potential",
"false potential",
"action potential",
"hidden potential"
] | C | |
SciQ | SciQ-1364 | homework, cell-membrane, human-physiology, lungs
Title: How many cell membranes are oxygen and carbon dioxide diffuse through in the lungs? In the lungs, oxygen and carbon dioxide pass through cell membranes by diffusion.
Which row is correct?
The correct answer is D, but I think it should be B. I can only think about three layers as maximum which are; epithelium of alveolus, endothelium of capillaries and the membrane of red blood cell. I don't know what are remainings.
Any help would be much appreciated! Oxigen goes from the alveolar's lumen to the cytoplasm of the erythrocyte, and that's 5 membranes:
the "top" of the alveolar epithelial cell
the "bottom" of such cell
the "top" of the endothelial cell (capillary)
the "bottom" of such cell
the erythrocyte membrane
You got all the cells right, but your only problem was this: oxygen diffuses through the cell membrane entering the cell, moves through the cytoplasm, and diffuses through the membrane again exiting the cell. So, for each cell, you have to count 2 membranes. For the last one, the erythrocyte, you have only 1 membrane (because it is $\ce{O2}$ final destination).
For the $\ce{CO2}$ the situation is a little bit more tricky. We have the same 4 membranes (2x epithelial cell and 2x capillary), but $\ce{CO2}$ can come from 2 locations:
from the erythrocyte, where it is formed from $\ce{H2CO3}$ (by the reaction $\ce{H2CO3 -> H2O + CO2}$) or released from the N-terminal group of proteins, like haemoglobin (where it has previously bound)
from the plasma (around 9% of the $\ce{CO2}$).
In the first case we have 5 membranes, and in the second case just 4.
So, the correct answer is D.
The following is multiple choice question (with options) to answer.
What two systems are the lungs part of? | [
"stomach and nervous",
"respiratory and excretory",
"stomach and excretory",
"heart and excretory"
] | B | The organs of the excretory system are also parts of other organ systems. For example, your lungs are part of the respiratory system. Your lungs remove carbon dioxide from your body, so they are also part of the excretory system. More organs of the excretory system are listed below ( Table below ). |
SciQ | SciQ-1365 | java, random
case 2:
return " with little to no vegitation, imports are what this town lives on.";
case 3:
return " and is full of fertile land, the farmers here are prosperous.";
case 4:
return " under the protection of large mountains and rought terrain; lining the horizon.";
case 5:
return " and the visible ocean water laps on the shore gentaly.";
case 6:
return " the visible ocean water is rough, and would be hard to navigate.";
case 7:
return " and strange jagged rocks protrude randomly along the landscape.";
case 8:
return " and purple glows eminate from a very large mountain peak in the far distance.";
case 9:
return " and colourful skys cause the buildings to shine with a great elegance.";
case 10:
return " built partially underground.";
default:
throw new IllegalStateException("Something went wrong!");
}
}
}
The following is multiple choice question (with options) to answer.
What occurs in a formerly inhabited area that was disturbed? | [
"natural selection",
"spontaneous mutation",
"mass extinction",
"secondary succession"
] | D | Secondary succession occurs in a formerly inhabited area that was disturbed. Soil is already in place, so pioneer species include small plants such as grasses. |
SciQ | SciQ-1366 | 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 can demonstrate the decrease in energy, biomass or numbers within an ecosystem? | [
"biomes",
"food chains",
"spontaneous mutation",
"ecological pyramids"
] | D | Ecological pyramids can demonstrate the decrease in energy, biomass or numbers within an ecosystem. Energy pyramids are discussed at http://www. youtube. com/watch?v=8T2nEMzk6_E (1:44). |
SciQ | SciQ-1367 | evolution, terminology, history, species, definitions
Title: Was Darwin aware of the difficulties behind the concept of species? Introduction
The concept of species is a very old concept that suffers from not being a natural category. There exists no single definition that would categorize living beings into groups and that would fit our intuitions of what a species should be.
Many of such problems in definitions are revealed in the field of evolutionary biology. For more information about the difficulties behind the definition of the concept of species, have a look at
How could humans have interbred with neanderthals if were a different species?
This post on ring species.
Question
Did Charles Darwin comment on this problem?
If yes, did Charles Darwin comment on the reason why he chose to keep using the term "species" instead of simply "lineage"? The whole point of Darwin's theory was that transition from one species to another is extremely slow and gradual. There are plenty of quotes in "Origin of Species" stating this, and also affirming that there is no clear boundary between species and subspecies, or "races".
Quotes from Origin of Species > Variation under Nature (Chapter 2)
Quote 1
Nevertheless, no certain criterion can possibly be given by which variable forms, local forms, sub species and representative species can be recognised
Quote 2
Several experienced ornithologists consider our British red grouse as only a strongly marked race of a Norwegian species, whereas the greater number rank it as an undoubted species peculiar to Great Britain. A wide distance between the homes of two doubtful forms leads many naturalists to rank them as distinct species; but what distance, it has been well asked, will suffice if that between America and Europe is ample, will that between Europe and the Azores, or Madeira, or the Canaries, or between the several islets of these small archipelagos, be sufficient?
Quote 3
It is here the most definitive quote I managed to find and partially answers to your second question.
From these remarks it will be seen that I look at the term species as one arbitrarily given, for the sake of convenience, to a set of individuals closely resembling each other, and that it does not essentially differ from the term variety, which is given to less distinct and more fluctuating forms. The term variety, again, in comparison with mere individual differences, is also applied arbitrarily, for convenience sake.
The following is multiple choice question (with options) to answer.
What evolutionary concept characterizes a species by body shape and other structural features? | [
"primary speciation",
"spontaneous evolution theory",
"geologic species concept",
"morphological species concept"
] | D | |
SciQ | SciQ-1368 | blast, sequence-homology, refseq
Title: Duplicate long hits from PSI-BLAST I had a protein Refseq ID and I PSI-BLASTed this sequence against Refseq database. We all know that the Refseq is a Reference sequence database and it shouldn't have redundancy. After BLASTing my sequence, at first iteration I got 1000 hits and among them there were a lot of redundant sequences!
My sequence had 241 amino acids and I found a lot of sequences with 100% identity, 100% cover and 0 E-value exactly the same as my sequence but with different IDs. All of these IDs were from RefSeq! In other iterations and after adjusting format options, I got this redundancy with other sequences from other species. My sequence is related to a chain of a multichain protein (E.coli fumarate reductase)
For example, when using NP_418578 as a query, I found WP_078165098.1, WP_064226696.1, WP_062863447.1, WP_001401474.1 and other that were identical.
I want to know what is wrong with Refseq. Is it really a Reference sequence database? If it is, where does this redundancy come from and why? This is what is known as a feature, not a bug. Note that your identical proteins all have accessions starting with WP_. These are special "non-redundant proteins". Many sequences—particularly bacterial sequences—are identical between various different species so having a separate RefSeq entry for each of them would be inefficient. Therefore, RefSeq combines multiple such proteins into a single WP_ record. This is documented here (emphasis mine):
The following is multiple choice question (with options) to answer.
What determines the unique sequence for every protein? | [
"space encoding",
"gene encoding",
"form encoding",
"variation encoding"
] | B | The unique sequence for every protein is ultimately determined by the gene encoding the protein. A change in nucleotide sequence of the gene’s coding region may lead to a different amino acid being added to the growing polypeptide chain, causing a change in protein structure and function. In sickle cell anemia, the hemoglobin β chain (a small portion of which is shown in Figure 3.26) has a single amino acid substitution, causing a change in protein structure and function. Specifically, the amino acid glutamic acid is substituted by valine in the β chain. What is most remarkable to consider is that a hemoglobin molecule is made up of two alpha chains and two beta chains that each consist of about 150 amino acids. The molecule, therefore, has about 600 amino acids. The structural difference between a normal hemoglobin molecule and a sickle cell molecule—which dramatically decreases life expectancy—is a single amino acid of the 600. What is even more remarkable is that those 600 amino acids are encoded by three nucleotides each, and the mutation is caused by a single base change (point mutation), 1 in 1800 bases. |
SciQ | SciQ-1369 | food, decomposition
Title: Worm compost cannot have cooked food I live in the Netherlands and it is getting fashionable to compost with worms. After investigating a few websites I noticed that most websites suggested that I cannot feed the worms leftovers from citrus fruits. This seems logical. I then started noticing that people advise against feeding the worms cooked food.
I'm no biologist but I cannot imagine a reason why cooked food is bad for the worms. Could anybody explain why this might be in layman’s terms? There are a few reasons for not feeding cooked foods to worms (Eisenia spp.) in a smaller household size worm farm. It's not because the food is cooked but what it often contains.
The earthworm used in vermiculture is usually Eisenia fetida (red wigglers) though other Eisenia species are sometimes used. All Eisenia are epigeic species meaning they live in the junction of decomposing organic matter (such as leaf litter, aging manure, rotted fallen trees) and their natural food is decaying plant matter and bacteria that are also digesting the organic matter. They don't make use of small dead animals (meat and fat).
In large scale commercial vermiculture operations, leftover and past-due-date foods from restaurants, institutions, nursing homes and schools are used along with plant matter and carboard and paper. I'm not sure how they balance cooked foods but possibly much less is used than plant matter.
The fact food is cooked isn't the problem but what's in it and/or what happens to it when added to the bin. If you have leftover vegetables and fruit that's been cooked with no added salt, it's perfectly acceptable. A certain amount of sweetened cooked fruit is also fine as the worms will eat that too. But ready-made foods usually have preservatives, salt, fats and spices added. Either worms won't eat it, leading to odour caused by mouldy rotten food, or it can make them unthrifty and even killing off your worms if it's fed them repeatedly.
The following is multiple choice question (with options) to answer.
By breaking down organic matter, roundworms play an important role in which cycle? | [
"metamorphic cycle",
"circadian cycle",
"carbon cycle",
"water cycle"
] | C | Roundworms may be free-living or parasitic organisms. Free-living worms are found mainly in freshwater habitats. Some live in moist soil. They generally feed on bacteria, fungi, protozoa, or decaying organic matter. By breaking down organic matter, they play an important role in the carbon cycle. |
SciQ | SciQ-1370 | homework, cell-membrane, human-physiology, lungs
Title: How many cell membranes are oxygen and carbon dioxide diffuse through in the lungs? In the lungs, oxygen and carbon dioxide pass through cell membranes by diffusion.
Which row is correct?
The correct answer is D, but I think it should be B. I can only think about three layers as maximum which are; epithelium of alveolus, endothelium of capillaries and the membrane of red blood cell. I don't know what are remainings.
Any help would be much appreciated! Oxigen goes from the alveolar's lumen to the cytoplasm of the erythrocyte, and that's 5 membranes:
the "top" of the alveolar epithelial cell
the "bottom" of such cell
the "top" of the endothelial cell (capillary)
the "bottom" of such cell
the erythrocyte membrane
You got all the cells right, but your only problem was this: oxygen diffuses through the cell membrane entering the cell, moves through the cytoplasm, and diffuses through the membrane again exiting the cell. So, for each cell, you have to count 2 membranes. For the last one, the erythrocyte, you have only 1 membrane (because it is $\ce{O2}$ final destination).
For the $\ce{CO2}$ the situation is a little bit more tricky. We have the same 4 membranes (2x epithelial cell and 2x capillary), but $\ce{CO2}$ can come from 2 locations:
from the erythrocyte, where it is formed from $\ce{H2CO3}$ (by the reaction $\ce{H2CO3 -> H2O + CO2}$) or released from the N-terminal group of proteins, like haemoglobin (where it has previously bound)
from the plasma (around 9% of the $\ce{CO2}$).
In the first case we have 5 membranes, and in the second case just 4.
So, the correct answer is D.
The following is multiple choice question (with options) to answer.
In the lungs, oxygen diffuses out of the alveoli and into where? | [
"neurons",
"capillaries",
"cillia",
"blood"
] | B | In the lungs, oxygen diffuses out of the alveoli and into the capillaries surrounding the alveoli. Oxygen (about 98 percent) binds reversibly to the respiratory pigment hemoglobin found in red blood cells (RBCs). RBCs carry oxygen to the tissues where oxygen dissociates from the hemoglobin and diffuses into the cells of the tissues. More specifically, alveolar P O 2. |
SciQ | SciQ-1371 | nitrogen
Step three is when plants and the animals that live of the plants die and breaks down into ammonia and other waste products (this is where many explanations of the nitrogen cycle usually starts). The waste products gets converted into ammonia by bacteria and the ammonia gets converted to nitrite and the entire cycle starts all over again.
Legumes have a symbiotic relationship with some bacteria that can fixate nitrogen (N2) https://aces.nmsu.edu/pubs/_a/A129/
sources:
https://science.howstuffworks.com/life/biology-fields/nitrogen-cycle.htm
https://www.britannica.com/science/denitrifying-bacteria
The rest is from my memory.
The following is multiple choice question (with options) to answer.
What term is used to describe animals that excrete ammonia? | [
"ammonstand",
"spirogyra",
"ammonotelic",
"xerophyte"
] | C | 41.4 | Nitrogenous Wastes By the end of this section, you will be able to: • Compare and contrast the way in which aquatic animals and terrestrial animals can eliminate toxic ammonia from their systems • Compare the major byproduct of ammonia metabolism in vertebrate animals to that of birds, insects, and reptiles Of the four major macromolecules in biological systems, both proteins and nucleic acids contain nitrogen. During the catabolism, or breakdown, of nitrogen-containing macromolecules, carbon, hydrogen, and oxygen are extracted and stored in the form of carbohydrates and fats. Excess nitrogen is excreted from the body. Nitrogenous wastes tend to form toxic ammonia, which raises the pH of body fluids. The formation of ammonia itself requires energy in the form of ATP and large quantities of water to dilute it out of a biological system. Animals that live in aquatic environments tend to release ammonia into the water. Animals that excrete ammonia are said to be ammonotelic. Terrestrial organisms have evolved other mechanisms to excrete nitrogenous wastes. The animals must detoxify ammonia by converting it into a relatively nontoxic form such as urea or uric acid. Mammals, including humans, produce urea, whereas reptiles and many terrestrial. |
SciQ | SciQ-1372 | ecology
I have tried to find explanatory texts both in this and other books without any success so my question is how's this balanced state achieved in both types of successions (the answer is hinted in the first paragraph which I don't quite understand)?
Related to my last post. The author is saying that 1) Mature ecosystems tend to have a balance between production (=P) and use (=R, respiration) of biomass. This is actually tautological because the author would probably define a mature ecosystem as one where this is true (P=R).
If it starts out P > R, the autotrophs are dominant: more biomass is being produced than used up. It is possible, for a time, that P will increase as, for example, plants grow more leaves, but R is growing too, and there is an eventual limit on P, which at maximum depends on the light available to the ecosystem. As biomass grows, so does the amount of biomass to potentially decay, so eventually R will always catch up to P, until there is balance.
If it starts out P < R, that means you are using up biomass faster than you are creating it. This case is even simpler: you will gradually run out of biomass, and R will decrease.
In either case, when the author is talking about P = R, this is going to be in relative terms; there might still be variations between them, for example seasonal variation, but on average over years or decades you would expect P = R in a mature, stable ecosystem.
The following is multiple choice question (with options) to answer.
The numbers and types of species in most ecosystems change to some degree through time and this is called? | [
"physiological succession",
"ecological succession",
"environmental succession",
"continuous succession"
] | B | Imagine walking in the forest in Figure below . The towering trees have been growing here for hundreds of years. It may seem as though the forest has been there forever. But no ecosystem is truly static. The numbers and types of species in most ecosystems change to some degree through time. This is called ecological succession. Important cases of ecological succession are primary succession and secondary succession. |
SciQ | SciQ-1373 | evolution, dna, theoretical-biology, genomes, species
Title: Biodiversity is restricted by genome combinatorics? Me and some friends are interested in opinions for the following:
Conjecture
The maximum number of species must be limited by the maximum
combinatorial/permutational space that can be occupied by DNA. Thus if
there is a maximum physical genome size this is what will determine
the maximum number of species that can possibly exist.
Explanation
E.G. say maximum number of DNA base pairs able to fit in a genome was $3$, each base pair can be one of either ${A,G,T,C}$. Then there are $4^3 = 64$ possible combinations of genomes. Extrapolate to genome sizes of $x$ base pairs, then there are $4^x$ combinations.
Questions
Would it be possible to claim that the underlying "blueprint" that codes for living diversity sets the absolute maximum for the total "diversity space"?
**Does it make sense to define the total number of species life can achieve with the simple function:
$S < 4^x$, where X is the maximum genome size measured in DNA base pairs?**
Notable Comments
The following is multiple choice question (with options) to answer.
The enormous number of species is due to the tremendous variety of what? | [
"measurements",
"tissues",
"sounds",
"environments"
] | D | The enormous number of species is due to the tremendous variety of environments in which they can live. |
SciQ | SciQ-1374 | equilibrium, catalysis
Figure 1 (source: Chemguide.co.uk) Your realisation is correct and something chemistry teachers try to hammer into their students’ heads time and time again (and yet, the point is still often lost):
Catalysts will never change the thermodynamics of a reaction. They only ease the path of the reaction. Forward and backward reactions will be accelerated equivalently.
So what is the benefit of a catalyst? There are multiple ones.
Speed
Take for example the Haber-Bosch process to synthesise ammonia from nitrogen and hydrogen.
$$\ce{N2 + 3 H2 <=> 2 NH3}\tag{1}$$
$$\Delta_\mathrm{r} H^0_\mathrm{298~K} = -45.8~\mathrm{\frac{kJ}{mol}}$$
This reaction is exothermic and thus should, theoretically or thermodynamicly, proceed spontaneously, e.g. if you mixed nitrogen and hydrogen in the appropriate ratio and added a spark. It does not, however. Significant activation energy is required to cleave the $\ce{N#N}$ triple bond.
Typical methods to add activation energy include heating. In the Haber-Bosch process, the mixture is heated to $400$ to $500~\mathrm{^\circ C}$ to supply the required activation energy. However, since the reaction is exothermic, heating will favour the reactant side. Increasing the pressure improves the entropic term of the Gibbs free energy equation, hence why pressures of $15$ to $25~\mathrm{MPa}$ are used.
Catalysts, based on iron with different promotors, are used to accelerate the reaction. By using catalysts, one can lower the temperature required in a trade-off between speed of reaction and favouring the product side of the equilibrium. With the conditions and catalysts used, one achieves a yield of $\approx 15~\%$ of ammonia within a reasonable timeframe. Not employing a catalyst would give much lower yields at much longer timeframes — economically much less feasible.
Direct reaction path not accessable
The following is multiple choice question (with options) to answer.
What is the energy needed to start a reaction between catalysts and reactants called? | [
"conductivity energy",
"activation energy",
"decomposition energy",
"reaction energy"
] | B | Catalysts interact with reactants so the reaction can occur by an alternate pathway that has a lower activation energy. Activation energy is the energy needed to start a reaction. When activation energy is lower, more reactant particles have enough energy to react so the reaction goes faster. Many catalysts work like the one in the Figure below . (You can see an animated version at the following URL. ) The catalyst brings the reactants together by temporarily bonding with them. This makes it easier and quicker for the reactants to react together. Notice how the catalyst is released by the product molecule at the end of the reaction. |
SciQ | SciQ-1375 | human-biology, digestive-system, immune-system, microbiome
The next level of defense comes from the cells of the innate immune system (14). In innate immunity, specialized cells monitor the area they are in for Pathogen-Associated Molecular Patterns (PAMPs). PAMPs can be sugars that make up the cell walls of the microbe or proteins that get expressed on the surface of the organism, such as Flagellin, a protein only found in the flagella of certain pathogen. The innate immune cells have pattern recognition receptors (PRR) that have a general specificity for recognizing and responding to the PAMPs. Our cells even have PRRs for DNA and Double Stranded RNA's, however those are usually found in vesicles on the inside of the cell. These interactions are very general, however once PRRs bind to the PAMP, they are able to signal into the cytoplasm, which can lead to the production of proteins, among other possible responses.
Here you can think of PRRs like a motion detector in a security system; the dog, or your two year old, or an intruder are going to set off the alarm just the same. It is not specific. The motion sensor "knows" that something that it is supposed to recognize, i.e. a moving object larger than a mouse passed by and it triggered the response, but it cannot tell you which moving object triggered it, only that it was triggered.
The innate immune cells are also able to respond by "eating" the pathogen in a process called phagocytosis. Here, they break up the bacteria, yeast, or the remnants of other dead host cells or large pathogens, things like worms, and put the broken up pieces on protein molecules on their surface.
When innate immune cells do this, they are presenting molecules to specialized immune cells (adaptive immune cells (14)), B-Cells and T-Cells, that are highly specific as to what they will react to. These cells can also cause a lot of damage to the host, so they are tightly regulated. Think of the interactions as keys and locks. A protein from a bacteria should turn a few of these cells on, but a protein from the host should not fit the lock.
The following is multiple choice question (with options) to answer.
Which proteins bind to the surfaces of microorganisms and are particularly attracted to pathogens that are already tagged by the adaptive immune system? | [
"mobilize proteins",
"complement proteins",
"attractive proteins",
"whereby proteins"
] | B | Complement An array of approximately 20 types of proteins, called a complement system, is also activated by infection or the activity of the cells of the adaptive immune system and functions to destroy extracellular pathogens. Liver cells and macrophages synthesize inactive forms of complement proteins continuously; these proteins are abundant in the blood serum and are capable of responding immediately to infecting microorganisms. The complement system is so named because it is complementary to the innate and adaptive immune system. Complement proteins bind to the surfaces of microorganisms and are particularly attracted to pathogens that are already tagged by the adaptive immune system. This “tagging” involves the attachment of specific proteins called antibodies (discussed in detail later) to the pathogen. When they attach, the antibodies change shape providing a binding site for one of the complement proteins. After the first few complement proteins bind, a cascade of binding in a specific sequence of proteins follows in which the pathogen rapidly becomes coated in complement proteins. Complement proteins perform several functions, one of which is to serve as a marker to indicate the presence of a pathogen to phagocytic cells and enhance engulfment. Certain complement proteins can combine to open pores in microbial cell membranes and cause lysis of the cells. |
SciQ | SciQ-1376 | evolution, species, molecular-evolution, species-distribution, macroevolution
Lalage leucopygialis, L. nigra, and L. sueurii: Species of triller birds that coexist on Sulawesi Island.
The existence of ring species like this can, as biologist Ernst Mayr puts it, illustrate "how new species can arise through 'circular overlap', without interruption of gene flow through intervening populations…" and offers proof of speciation through a method other than allopatric speciation: speciation that happens when two populations of the same species become isolated from each other due to geographic changes.
The following is multiple choice question (with options) to answer.
What type of competition occurs between members of the same species? | [
"intraspecific",
"exospecies",
"interspecies",
"interspecific"
] | A | Intraspecific competition occurs between members of the same species. For example, two male deer may compete for mates by clashing their antlers together. |
SciQ | SciQ-1377 | human-genetics, population-dynamics, population-biology, population-genetics
Generations are non-overlapping. A more realistic model would need to consider $t$ as a continuous variable a give a probability of reproducing which depend on the age of the individual.
Never two related individuals mate together. Otherwise, you paternal grandfather might be your maternal grandfather. In reality we are all somehow related, we have a common ancestor (Hey Bro). For example if you consider that your parents are siblings and that their parents are siblings and so forth… then you don't need more than 2 great-great-great-great-grandparents. In order to keep track of such events (inbreeding), you need a stochastic model and you would need to know the population size $N(t)$ as a function of $t$.
Tracking the change of population size through time is part of a very big in biology which is called population biology. For example you will find in this post a model of population growth of two interacting species (prey-predator)
The following is multiple choice question (with options) to answer.
Alternation of generations is characteristic of the life cycle of all what? | [
"cells",
"organs",
"plants",
"animals"
] | C | All plants have a characteristic life cycle that includes alternation of generations. Asexual reproduction with spores produces a haploid gametophyte generation. Sexual reproduction with gametes and fertilization produces a diploid sporophyte generation. |
SciQ | SciQ-1378 | cell-biology, molecular-genetics, eukaryotic-cells
Or perhaps these vectors sneak into the nucleus during mitosis? (This is a theory that just occurred to me when contemplating the "non-dividing" qualification in the Strachan quote.)
Since the question isn't addressed in the paper, I can only assume the answer is elementary and something that a professional cell biologist would be expected to know. I've run out of obvious next steps for finding the answer, so I beg pardon in advance for asking it. My attempt to find an answer has suggested that no-one knows how the DNA gets into the nucleus.
This fairly recent paper reports attempts to track the pathway of DNA entry and transfer to the nucleus.
The following is multiple choice question (with options) to answer.
What carries the instructions from the nucleus to the cytoplasm? | [
"concept rna",
"messenger rna",
"anderson rna",
"dirscriptor rna"
] | B | Messenger RNA ( mRNA ) carries the instructions from the nucleus to the cytoplasm. mRNA is produced in the nucleus, as are all RNAs. |
SciQ | SciQ-1379 | homework-and-exercises, pressure, unit-conversion
Restricting our attention to the pressure and height differences only, it's clear that $h=1$ millimetre of mercury corresponds to the pressure difference:
$$ \delta P = h \rho g = 0.001 \,{\rm m} \times 13,595.1\, {\rm kg}/{\rm m}^3 \times 9.80665\,{\rm m}/{\rm sec}^2 = 133.332 \,{\rm Pa} $$
The inverse relationship is 1 Pascal is equivalent to $1/133.332 = 0.0075006$ mmHg. The exact values of the densities are a little bit conventional - the densities depend on temperature and pressure and the gravitational acceleration depends on the place. In the past, 1 mmHg wasn't needed that accurately. In the modern era, we define 1 mmHg by your relationship, and 1 Pa is much more accurately defined in terms of "fundamental physics".
The following is multiple choice question (with options) to answer.
What is measured using units pascal, bar, atmosphere or mmhg? | [
"fuel",
"pressure",
"push",
"Muscle"
] | B | strong enough to keep the particles of substance together but not in place. Thus, the particles are free to move over each other but still remain in contact. In gases, the intermolecular interactions are weak enough that the individual particles are separated from each other in space. The kinetic theory of gases is a collection of statements that describe the fundamental behavior of all gases. Among other properties, gases exert a pressure on their container. Pressure is measured using units like pascal, bar, atmosphere, or mmHg (also called atorr). There are several simple relationships between the variables used to describe a quantity of gas. These relationships are called gas laws. Boyle’s law relates the pressure and volume of a gas, while Charles’s law relates the volume and absolute temperature of a gas. The combined gas law relates the volume, pressure, and absolute temperature of a gas sample. All of these gas laws allow us to understand the changing conditions of a gas. The ideal gas law relates the pressure, volume, amount, and absolute temperature of a gas under any conditions. These four variables are related to the ideal gas law constant, which is the proportionality constant used to calculate the conditions of a gas. Because the conditions of a gas can change, a set of benchmark conditions called standard temperature and pressure (STP) is defined. Standard temperature is 0ºC, and standard pressure is 1.00 atm. |
SciQ | SciQ-1380 | zoology, microbiology, pathology
Title: Prevention of disease spreading in animal kingdom It's my first question on here, so I'm not sure If my question fits the theme. Please refer me to the appropriate one, If I have made a mistake.
So a question that I wanted to ask has to do with whether or not animals potentially try to avoid spreading diseases. So I was thinking... In an event that a really deadly disease emerges in a population, it would be really dangerous for animals that live in social groups, of any size really, not to have any instinctual behaviours that try and prevent the disease to spread. Animals that live in big heads, like wildebeests would just probably leave the diseased individuals behind, apes and monkey could potentially cast out individuals from the group, etc. Ants have separate sections in their tunnels that serve as graveyards, I presume for this exact purpose.
A lot of parasitic organisms have adaptations that specifically target animals with social behaviour, so why wouldn't animals adapt against that?
Something that also came to my mind is that this could possibly evolve not as a social behaviour of a group, but sometimes that individuals in a group would do, for example self isolation. However, I do not find this likely, I possibly requires higher cognitive understanding of disease spread.
Am I way of base here? If not, could you please provide some interesting examples you are familiar with.
The following is multiple choice question (with options) to answer.
What is a disease that can be spread from animals to humans called? | [
"proteolysis",
"Anthroponosis",
"zoonosis",
"parasite"
] | C | Often, new diseases result from the spread of an existing disease from animals to humans. A disease that can be spread from animals to humans is called a zoonosis . When a disease breaks out, scientists called epidemiologists investigate the outbreak, looking for its cause. Epidemiologists are like detectives trying to solve a crime. The information epidemiologists learn is important to understand the pathogen, and help prevent future outbreaks of disease. |
SciQ | SciQ-1381 | particle-physics, mass-energy, higgs, quarks, subatomic
Title: Where does the mass of a nucleon originate in an atom? The mass of the three quarks in the nucleons make up only about one to two percent of the mass of the nucleons. What makes up the other 98 percent? From this wikipedia article:
In quantum chromodynamics, the modern theory of the nuclear force, most of the mass of the proton and the neutron is explained by special relativity. The mass of the proton is about 80–100 times greater than the sum of the rest masses of the quarks that make it up, while the gluons have zero rest mass. The extra energy of the quarks and gluons in a region within a proton, as compared to the rest energy of the quarks alone in the QCD vacuum, accounts for almost 99% of the mass. The rest mass of the proton is, thus, the invariant mass of the system of moving quarks and gluons that make up the particle, and, in such systems, even the energy of massless particles is still measured as part of the rest mass of the system.
Also, at about 5:00 of this youtube video by Veritasium is your same question answered.
This other physics.se question is also related.
The following is multiple choice question (with options) to answer.
Where does most of the mass for an atom reside? | [
"nucleus",
"electrons",
"protons",
"neutrons"
] | A | Electrons have virtually no mass, but protons and neutrons have a lot of mass for their size. As a result, the nucleus has virtually all the mass of an atom. Given its great mass and tiny size, the nucleus is very dense. If an object the size of a penny had the same density as the nucleus of an atom, its mass would be greater than 30 million tons! You can learn more about the size and mass of the nucleus at this URL:. |
SciQ | SciQ-1382 | electromagnetism, magnetic-fields
Title: Net magnetic field in various cases and if they're same Recently I've begun to study magnetism and I'm familiar with the fact that all wires (however ideal they may be) will have a magnetic field around them when they have current passing through them and hence all wires have inductance.
Now let's suppose we have a very long wire carrying some steady DC current.
We want to calculate the net magnetic field around a length $x$ along the wire(just a bit of imagination).
If at a point on the wire(starting point), we add all the magnetic fields (on the imaginary disk perpendicular to the wire at that point) from radius $0$ to $R$ where $R$ is the maximum radius after which the field is too weak to be noticed. Now this field will be constant for any nearby point if the wire is sufficiently long enough.
It will be
$$\frac{\mu_0I}{2\pi}\int_0^R\frac1 r dr$$
Let's now find the net field for the whole length $x$. (I'm not sure how to do that)
Now if we make a bit of that wire into a circle of perimeter $x$ the magnetic field around that loop will be like this.
The following is multiple choice question (with options) to answer.
When electric current flows through a wire, it creates what type of field that surrounds the wire in circles? | [
"thermal",
"gravitational",
"kinetic",
"magnetic"
] | D | Electromagnetism is magnetism produced by an electric current. When electric current flows through a wire, it creates a magnetic field that surrounds the wire in circles. You can see this in the diagram below. Note that electric current is conventionally shown moving from positive to negative electric potential, as in this diagram. However, electrons in current actually flow in the opposite direction, from negative to positive potential. |
SciQ | SciQ-1383 | 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 the outermost layer of the skin? | [
"nexus",
"callus",
"dermis",
"epidermis"
] | D | The epidermis is the outermost layer of the skin. It forms the waterproof, protective wrap over the body's surface. Although the top layer of epidermis is only about as thick as a sheet of paper, it is made up of 25 to 30 layers of cells. The epidermis also contains cells that produce melanin. Melanin is the brownish pigment that gives skin and hair their color. Melanin-producing cells are found in the bottom layer of the epidermis. The epidermis does not have any blood vessels. The lower part of the epidermis receives blood by diffusion from blood vessels of the dermis. |
SciQ | SciQ-1384 | waves
Title: Is wave motion the combined motion of the disturbance and the medium? Using a textbook slinky as an example, if the disturbance propagates through the slinky from left to right and the particles of the slinky vibrate up and down, does that mean 'wave motion' is also associated with the medium? Since the motion of the wave that we perceive is the combined motion of the disturbance and the medium? This answer is maybe not the most straightforward satisfactory answer to your stated question, but I think it anticipates ways of thinking that are used in more advanced areas of physics.
There are two pictures of what a wave is.
A wave is coherent motion in a medium; as time progresses energy moves through the medium and vibrations occur in different locations.
A wave is a propagating disturbance. It is not made of anything, the word "wave" refers a disturbance which propagates energy from one place to another.
Your question kind of implies that a wave is some combination of 1 and 2. I would say that either 1 or 2 are valid pictures, but you should treat them as distinct pictures of the same physical phenomenon and not reason about both simultaneously.
The advantage of the first picture is that it gives you a clear mechanical model of what is going on at a fundamental level; if you zoom in there are particles in the material, and the particles are oscillating back and forth in tandem -- that coherent motion is a wave. However, the disadvantage is that wave phenomena occur in many circumstances, and there are features of any particular example that will not generalize and can lead you astray if you take them too seriously. For example, light traveling in vacuum cannot be accurately visualized as motion of particles.
The advantage of the second picture is that it is more abstract and general -- wave phenomena occur in all kinds of materials, and so there is no need to specify which specific material you are thinking of, because we can make very general statements about waves that apply to any material. The disadvantage is that it can be hard to wrap your head around a disturbance without a medium, and also sometimes trying to be too general means you miss special aspects of the particular situation you might be interested in (for example, cool behavior like solitons can occur in water but not in light propagating in vacuum).
The following is multiple choice question (with options) to answer.
What is it called when waves spread out as they travel around obstacles or through openings in obstacles? | [
"diffraction",
"diffusion",
"destruction",
"absorption"
] | A | Diffraction occurs when waves spread out as they travel around obstacles or through openings in obstacles. |
SciQ | SciQ-1385 | inorganic-chemistry, redox
Title: Rust forming and being washed off by water I have noticed that, when exposed to water for a few days, the steel in my wagon turns into rust. After several more weeks, the rust that formed is dissolved in the water, and once I pour the water out there isn't any rust where there previously was rust.
This is unusual because iron oxides and iron hydroxides (the components of rust) don't normally dissolve in water, and so the water just keeps being reduced and the iron keeps being oxidized.
How can it apparently happen such that steel turns to rust, then back to steel with no rust, in the presence of water if rust does not normally dissolve in water?
This happens in a cycle like this:
steel + water = rust -> rust + water = steel + rusty water Rust appears because iron is oxidized in presence of oxygen (it is a oxydo-reduction reaction, meaning an electron transfer occurs between species), and water helps this phenomenon occur. Iron loses 3 electrons to the favour of the oxygen.
In presence of water, oxygen can oxidize iron by the mean of hydroxyl group. It leads to:
$$\ce{2Fe(OH)_3 \leftrightharpoons Fe_2O_3\cdot 3H_2O}$$
where water is not the oxidizer, rather it is a mediator for oxidation.
Hydroxides have low solubility, so water can only dissolve a small fraction of it.
On the other hand, poured water can abrade rust (via mechanical stress) and remove it of from the bulk metal, leaving the surface clean for producing more rust. This is how huge rods of metal can vanish in a few months in corrosive environmental conditions (such as wet air or water).
Preventing rust requires the use of specific alloys and surface finishing. You can also add a galvanic electrode (generally made of $\ce{Zn}$, a so-called sacrificial anode) to protect submerged metallic structures such as the hull of a boat.
Therefore, in your example water is both a mediator of oxidation and mechanical abrasion agent.
The following is multiple choice question (with options) to answer.
What is the process of oxidized iron that has been exposed to air and water? | [
"rust",
"crystallization",
"bark",
"crust"
] | A | After the ball of cells reaches the uterus, it fixes itself to the side of the uterus. This is called implantation . It usually happens about a week after fertilization. Now the implanted ball of cells is ready to continue its development into a baby boy or girl. |
SciQ | SciQ-1386 | electric-circuits, electric-current, electrical-resistance, voltage
Title: Current through two vertical ideal conductors Let's consider the circuit:
Do I understand correctly that current can't flow through these two vertical ideal conductors? (Voltage source and connecting conductors are assumed to be ideal (with zero resistance).)
I've just built the diagram, but it's not so:
I think this question refers to the non-trivial physical idea. I just want to understand the undefinity of currents in these loops. However, it seems that this uncertainty cannot be removed in any way. Each of those extra vertical conductors forms a loop and the current in the loop is the current in the extra conductor. There is no voltage drop anywhere on that loop and there is no resistance anywhere on the loop. So KVL is satisfied with any arbitrary amount of current going around the loop. There is nothing in the circuit diagram that constrains the loop current to be zero.
The following is multiple choice question (with options) to answer.
What consists of one or two closed loops through which current can flow? | [
"thermal reaction",
"cooling circuit",
"magnetic poles",
"electric circuit"
] | D | An electric circuit consists of one or two closed loops through which current can flow. It has a voltage source and a conductor and may have other devices such as lights and switches. |
SciQ | SciQ-1387 | 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.
What muscle is imperative to breathing in helping the air move in and out of the lungs? | [
"spleen",
"diaphragm",
"kidneys",
"uterus"
] | B | Breathing is the process of moving air into and out of the lungs. It depends on the muscle called the diaphragm. |
SciQ | SciQ-1388 | The first one gives the minimum volume, so you don't want that. Take the second.
-
Thank you Jerry. :) Cheers! You get the right answer, because you actually gave me two value and described them really nice! I could follow the process very easily! – user31113 Apr 7 '13 at 11:46
You're welcome! – Jerry Apr 7 '13 at 11:47
If you cut the corner in the manner shown, by trigonometry at any corner, the new side length is smaller by $2 \sqrt3 h$. (Let me know if you have difficulty with this.)
Hence the box's volume is proportional to $\left(a-2 \sqrt3 h\right)^2 h$, which we try to maximise. Let $V(h) = \left(a-2 \sqrt3 h\right)^2 (4 \sqrt3 h)$. The value of $h$ which maximises $V(h)$ is exactly same as that maximising the volume we desire, due to proportionality. Now $V(h)$ can be looked at as the product of $3$ terms, $(a-2 \sqrt3 h), (a-2 \sqrt3 h)$ and $(4 \sqrt3 h)$, which sum to a constant $2a$. Hence the product is maximised when these three terms are equal. i.e.
$a-2 \sqrt3 h = 4 \sqrt3 h$ or when $h = \dfrac{a}{6\sqrt3}$.
-
Oh woops, yours is definitely more elegant! – Jerry Apr 7 '13 at 11:26
@Jerry Thanks. It's just that I like inequalities a lot. – Macavity Apr 7 '13 at 11:32
Thank you Macavity. :) Cheers! – user31113 Apr 7 '13 at 11:44
@Macavity Your solution is certainly neat, but I get a slight butterfly feeling when you pull that factor out of the air. I seem to get the same numbers by a method at least I find simpler. Any comments? – Brian Chandler Dec 20 '14 at 16:24
The following is multiple choice question (with options) to answer.
What third property is different if two boxes have the same volume but one has greater mass? | [
"oxygen",
"density",
"output",
"diameter"
] | B | A: Both boxes have the same volume because they are the same size. However, the books have greater mass than the feathers. Therefore, the box of books has greater density. |
SciQ | SciQ-1389 | electromagnetism, charge
You may ask why it is then so contrary to speak that two opposite charges cancel each other. No objection. All I want you to remember is that it is the net charge that is zero. Individually the charges are not zero. Take the example of an ionic crystal, say $NaCl$, where $Na^+$ and Cl^-$ ions are tightly held together by electrostatic attraction. Both ions have equal and opposite charges. If the interaction between the two lead to the individual destruction of charges (losing property as a charge), then how the solid continues to be so brittle. There is always interaction between the two ions. This means the interaction between the two charges do not cause the charges to lose their charge. It's the effective charge that is zero. We then speak about a system, not about individual charges.
The following is multiple choice question (with options) to answer.
What occurs when two opposite charges are separated by some amount of distance? | [
"diffusion",
"radioactivity",
"dipole",
"particle"
] | C | A dipole occurs when two opposite charges are separated by some amount of distance. We have already seen dipoles in the form of polar bonds. For example, each O-H bond in water is an example of a dipole; the partial positive charge on hydrogen is separated from the partial negative charge on oxygen by the length of the bond. A molecular dipole is the geometric sum of all the individual bond dipoles in a molecule. In order for a molecule to have a dipole, it must have at least one polar bond. However, not all molecules with polar bonds have an overall molecular dipole. Sometimes the dipoles within a molecule will effectively cancel each other out, giving a zero net molecular dipole. This is often seen in symmetrical molecules. |
SciQ | SciQ-1390 | cell-division
Title: Why doesn't cellular, replicative senescence (or the hayflick limit) constrain the normal development of an organism? The wikipedia article on cellular senescence states:
Cellular senescence is the phenomenon by which normal diploid cells cease to divide. In culture, fibroblasts can reach a maximum of 50 cell divisions before becoming senescent. This phenomenon is known as "replicative senescence", or the Hayflick limit.
The following is multiple choice question (with options) to answer.
What is the term for the span in the life of an organism from one generation to the next? | [
"life cycle",
"time consumption",
"life span",
"era"
] | A | Eukaryotes have three different versions of the sexual life cycle : a haploid life cycle, a diploid life cycle, and a life cycle known as the alternation of generations ( Figure below ). A life cycle is the span in the life of an organism from one generation to the next. All species that reproduce sexually follow a basic pattern, alternating between haploid and diploid chromosome numbers. The sexual life cycle depends on when meiosis occurs and the type of cell that undergoes meiosis. |
SciQ | SciQ-1391 | hydrology, mountains, rivers
Title: Why do rivers have 'wells' in mountains? Why/how can rivers have sources in places high above the sea level? The presence of water underground has nothing to do with sea level in mountainous country.
When rain fails on a mountain, or snow falls on a mountain and the snow eventually melts, the water from the rain or snow melt mostly travels downhill via rivers to the sea.
In getting to a river some of the water will fall on the ground. In places where the ground is covered by soil, water can travel through the soil via the pore spaces between the grains of soil. Similarly if porous rock, such as sandstone lies beneath the soil water can travel through the pores in the rock.
If a layer of impervious rock lies under the porous rock or soil, the water cannot move downwards, due to gravity, any further. This can lead to water accumulating in the soil or porous rock and saturating the soil or rock. In such situations an aquifer can form. The top of the saturated zone in an aquifer is called a water table.
The ground beneath a river is saturated and the surface of the river shows the water table exposed to atmosphere. Thus in mountainous regions the ground beneath rivers will be saturated and capable of supporting a well developed from the bank of a river.
The following is multiple choice question (with options) to answer.
Deposition also occurs when a stream or river empties into a large body of what? | [
"calm water",
"still water",
"homogeneous water",
"even water"
] | B | Deposition also occurs when a stream or river empties into a large body of still water. In this case, a delta forms. A delta is shaped like a triangle. It spreads out into the body of water. An example is pictured below ( Figure above ). |
SciQ | SciQ-1392 | 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 is the process called in which nutrients pass into the bloodstream? | [
"accumulation",
"accumulation",
"incorporation",
"absorption"
] | D | After food is digested, the resulting nutrients are absorbed. Absorption is the process in which substances pass into the bloodstream, where they can circulate throughout the body. Absorption of nutrients occurs mainly in the small intestine. Any remaining matter from food that cannot be digested and absorbed passes into the large intestine as waste. The waste later passes out of the body through the anus in the process of elimination . |
SciQ | SciQ-1393 | zoology, terminology, nomenclature, invertebrates, etymology
Urochorda
Cephalochorda
Craniata
which is more or less the accepted division today, with Urochorda being called Urochordata now.
In this essay, Lankester says:
The evidence of degeneration is admitted as conclusive in the case of the parasitic Crustacea and Cirrhipedes. It is equally incontestable in that very large and varied group of non-parasitic organisms, the Tunicata (Urochordate Vertebrata).2
(in the above 'Vertebrata' is what we call 'Chordata'). He adds this footnote:
2The whole argument as to the Tunicates of course rests on the view- supported by many arguments, that the larval urochord, which many of
them possess, is not a larval organ acquired by larval adaptation, but is hereditary and transmitted from adult ancestors.
The term 'urochord' seems to be established and used without comment there, and probably is taken as simple neo-Latin for 'tail chord', although that may be somewhat loose, perhaps meaning the notochord is present but does not extend into the head. A 1913 Webster's Dictionary defines urochord as:
(Zool.) The central axis or cord in the tail of larval ascidians and of certain adult tunicates.
In 1882, Lankester futher discussed the anatomy of the tunicates in the context of the division of the chordata in a paper called "The Vertebration of the Tail of Appendiculariæ". This paper includes an illustration of a larval tunicate with the "notochord (urochord)" indicated.
The following is multiple choice question (with options) to answer.
The colloquial term "ribbon worm" refers to the mostly marine species of what phylum? | [
"gnathifera",
"lophophorata",
"nematoida",
"nemertea"
] | D | Phylum Nemertea The Nemertea are colloquially known as ribbon worms. Most species of phylum Nemertea are marine, predominantly benthic or bottom dwellers, with an estimated 900 species known. However, nemertini have been recorded in freshwater and terrestrial habitats as well. Most nemerteans are carnivores, feeding on worms, clams, and crustaceans. Some species are scavengers, and some nemertini species, like Malacobdella grossa, have also evolved commensalistic relationships with some mollusks. Some species have devastated commercial fishing of clams and crabs. Nemerteans have almost no predators and two species are sold as fish bait. Morphology Ribbon worms vary in size from 1 cm to several meters. They show bilateral symmetry and remarkable contractile properties. Because of their contractility, they can change their morphological presentation in response to environmental cues. Animals in phylum Nemertea show a flattened morphology, that is, they are flat from front to back, like a flattened tube. Nemertea are soft and unsegmented animals (Figure 28.18). |
SciQ | SciQ-1394 | molecular-genetics, human-genome
Title: Criteria for the numbering of human chromosomes What were the criteria devised for the numbering convention employed in human chromosomes? When was it fixed?
Correct me if I am wrong; it appears that chromosome pairs 1 to 22 were originally ordered in terms of perceived structural size, which ended up fitting neatly with the quantity of base pairs (but not with the quantity of genes).
The sex chromosomes in turn were arbitrarily assigned as "pair 23".
Is this sound?
Thanks in advance. Why do you think it was "fixed?" Here's a nice review of the history of human cytogenetics, which included not only the original image from 1956 but points out a report which comments on the standardization of chromosome number. The autosomes were indeed numbered by length, and the sex chromosomes are traditionally put at the end as they are "numbered" 23 but clearly function quite differently. Gene content was decades away from being known at the time, and honestly isn't even known now. It's also just as arbitrary; simple size is easy enough and makes for rather nice pictures.
The following is multiple choice question (with options) to answer.
The number, size, shape, and banding pattern of chromosomes make them easily identifiable in a karyogram and allow for the assessment of many chromosomal | [
"nutrients",
"processes",
"abnormalities",
"beliefs"
] | C | 7.3 Errors in Meiosis The number, size, shape, and banding pattern of chromosomes make them easily identifiable in a karyogram and allow for the assessment of many chromosomal abnormalities. Disorders in chromosome number, or aneuploidies, are typically lethal to the embryo, although a few trisomic genotypes are viable. Because of X inactivation, aberrations in sex chromosomes typically have milder effects on an individual. Aneuploidies also include instances in which segments of a chromosome are duplicated or deleted. Chromosome structures also may be rearranged, for example by inversion or translocation. Both of these aberrations can result in negative effects on development, or death. Because they force chromosomes to assume contorted pairings during meiosis I, inversions and translocations are often associated with reduced fertility because of the likelihood of nondisjunction. |
SciQ | SciQ-1395 | biochemistry, biophysics, bioenergetics
Title: Are there known life forms that are able to transform mechanical energy into chemical energy? Are there known life forms that are able to transform mechanical energy into chemical energy?
This question asks a similar subject, but more specific and has no answers.
The background of this question are thoughts about hypothetical life on tidally locked exoplanets of red dwarf stars, where light for photosynthesis is scarce but mechanical energy (storms and/or water currents) aplenty. There are no known life forms that use mechanical energy as a primary form of metabolic energy (i.e., for generic cellular functions). Many life forms are sensitive to mechanical disruption in some way, so they do utilize mechanical energy, but in a very limited fashion (@David's answer touches on this), and of course many organisms have life cycles that somehow depend on mechanical transportation (seed/spore dispersal, traveling on the wind or ocean currents, etc).
I think the main physical problem is that mechanical energy just isn't available to biological cells in a form that can be converted to substantial chemical energy. They are small, and tend to have other great benefits for being small.
To use an ocean wave as an example, there is very little or no perceptible movement for a cell in that wave, besides an apparent increase and decrease in the force of gravity. The top and bottom of the cell are moving together with the flow of water, so there is no differential to operate on.
An E. coli weighs about 1 picogram. If it could capture all of the energy from falling from 1km in the air on earth, assuming no uncaptured aerodynamic drag, that would be about 10-11 joules.
If there are ~3000 kJ/mol of energy available from burning glucose, that means about 5 × 10-21 joules per molecule of glucose, so about 20 billion glucose molecules, which sounds like a lot but it is only 1 femtogram, 0.1% the weight of the cell.
The following is multiple choice question (with options) to answer.
The logistics of carrying out cellular metabolism sets limits on what physical property of the cell? | [
"layer",
"composition",
"surface",
"size"
] | D | |
SciQ | SciQ-1396 | planets, definition, asteroids
Title: What is the current status of Pluto? Pluto has been designated a planet in our solar system for years (ever since it was discovered in the last century), but in 2006 it was demoted.
What caused this decision? And is there a chance that it could be reversed?
Edit: well, http://www.dailygalaxy.com/my_weblog/2017/03/nasas-new-horizon-astronomers-declare-pluto-is-a-planet-so-is-jupiters-ocean-moon-europa.html is interesting; this is science, so anything could (potentially) change. Pluto is now classified as a dwarf planet. The main difference between a planet and a dwarf planet has to do with the requirement that a planet clear out the material in and near its orbit. Planets do this, dwarf planets do not.
The reclassification was triggered by the discovery of many additional object (the Edgeworth-Kuiper Belt) out beyond the orbit of Neptune. Some of the objects are nearly as big as (and is a few cases, possibly bigger than) Pluto and in very similar orbits. Thus it was realized that Pluto was just the largest of a large number of objects in the outer solar system.
This is simply science at work. At the local university, we have an Astronomy textbook from the 1800's that lists the 12 planets: Mercury, Venus, Earth, Mars, Ceres, Pallas, Juno, Vesta, Jupiter, Saturn, Uranus, and Neptune. However, as more objects were detected between Mars and Jupiter, it was realized this was a new class of object and the middle four were downgraded from planet status to asteroids. It is the same process at work today out in the outer solar system.
The following is multiple choice question (with options) to answer.
What large dwarf planet in our solar system was only discovered in 2005? | [
"Cerus",
"zeus",
"eris",
"artemis"
] | C | Eris is the largest known dwarf planet in the solar system. It is 27 percent larger than Pluto ( Figure above ). Like Pluto and Makemake, Eris is in the Kuiper belt. But Eris is about three times farther from the Sun than Pluto. Because of its distance, Eris was not discovered until 2005. Early on, it was thought that Eris might be the tenth planet. Its discovery helped astronomers realize that they needed a new definition of “planet. ” Eris has a small moon that orbits Eris once about every 16 days. |
SciQ | SciQ-1397 | enthalpy
Title: Determining the Average Bond Enthalpy for the C-F bond Given the following data, how would you work out the average bond enthalpy for $\ce{C-F}$ bond. I've tried setting up the chemical equations and applying Hess's Law, but that's not getting me anywhere.
$\Delta H_\mathrm f^\circ(\ce{CF4(g)})=-680~\mathrm{kJ~mol^{-1}}$
Bond enthalpy, $\ce{F2(g)}=+158~\mathrm{kJ~mol^{-1}}$
$$\ce{C(s) -> C(g)}\quad \Delta H=+715~\mathrm{kJ~mol^{-1}}$$
EDIT: These are the equations I used:
$$\begin{align}
\ce{C(s) + 2F2(g) &-> CF4(g)}\\[6pt]
\ce{F2(g) &-> 2F-(g)}\\[6pt]
\ce{C(s) &-> C(g)}
\end{align}$$ Your approach to use Hess's Law is reasonable!
\[\Delta H_r = -680 - (715 + 2\cdot158) = -1711\ \mathrm{kJ\cdot mol^{-1}}\]
That's the enthalpy for $\ce{CF4}$ - a molecule with four $\ce{C-F}$ bonds.
The average $\ce{C-F}$ bond enthalpy is smaller:
\[\frac{1711}{4}\ \mathrm{kJ\cdot mol^{-1}} \approx 427\ \mathrm{kJ\cdot mol^{-1}}\]
The following is multiple choice question (with options) to answer.
Covalent bond energies can be used to estimate the enthalpy changes of what? | [
"liquid reactions",
"Pressure reactions",
"crystals reactions",
"chemical reactions"
] | D | Covalent bond energies can be used to estimate the enthalpy changes of chemical reactions. |
SciQ | SciQ-1398 | evolution, mammals
Title: Why haven't land animals evolved beyond urination? It occurred to me (while urinating) that this would seem to be selected against because water is a scarce resource. Why are we constantly losing water we don't need to through urination? What is it about the chemistry of urine and the waste products eliminated that make urination necessary as opposed to eliminating them through defecation and recovering the water on the way out? It is probably true that toilets and other resting-ish area are always a great place to think about biology, I agree $\ddot \smile$.
Why do we urinate?
In short, urine contains the waste from our blood while defecation is just the stuff that we haven't digested. Kidneys are the organs responsible for draining wastes (mostly nitrogen-containing, or nitrogenous, wastes) from our blood.
Trade-off: energy cost vs. water loss
You're correct that the loss of water through urination is a considerable cost for an organism (especially those living in dry environments). But the amount of water used to excrete nitrogenous wastes is negatively correlated with the energy it costs to perform this excretion. In other words, there is a trade-off between water and energy loss during nitrogen excretion. Also, the question of toxicity is important.
Three ways to excrete nitrogenous wastes
Animals basically have three choices to excrete nitrogenous wastes:
Uric acid (excreted by uricotelic organisms)
Solid (crystal) with low water solubility
Low toxicity
Little water is needed
Lots of energy is needed
Ammonia (excreted by aminotelic organisms)
Highly soluble in water
High toxicity
Lots of water is needed to dilute it because of the toxicity
Not much energy is needed
Urea (excreted by ureotelic organisms)
Solid but highly soluble in water
"medium" amount of water is needed
"medium" toxicity
"medium" amount of energy is needed
The following is multiple choice question (with options) to answer.
What type of waste is eliminated from the body through the anus? | [
"liquid",
"urine",
"solid",
"carbon dioxide"
] | C | solid waste that remains after food is digested and is eliminated from the body through the anus. |
SciQ | SciQ-1399 | mycology
Does this mean that not only is going to the swimming pool not a cure of fungal infections, but it is actually the cause? Well, maybe not. While the articles show that there is a larger incidence of fungal infections among swimmers, they only show correlation, not causality. People who partake in sports activities have a bigger chance of having these infections than the general public. These are also the people who are more likely to go swimming.
To settle the matter for good, we need an article named "Prevalence of fungal infections among occasionally swimming couch potatoes" :-)
The following is multiple choice question (with options) to answer.
Fungi cause three different types of human illness: poisonings, parasitic infections, and what? | [
"allergies",
"diarrhea",
"heart disease",
"diabetes"
] | A | Fungi cause three different types of human illness: poisonings, parasitic infections, and allergies. Many poisonous mushrooms are eaten by mistake because they look like edible mushrooms. Parasitic yeasts cause candidiasis, ringworm, and athlete’s foot. Mold allergies are very common. |
SciQ | SciQ-1400 | genetics, dna, dna-sequencing, human-genetics
Title: Do eukaryote cells contain DNA that isn't part of a chromosome or located in the mitochondria? I specify eukaryote in the title, but I'm also interested if this question isn't applicable to eukaryote cells in general but is to humans. I was reading "RNA-seq: An assessment of technical reproducibility and comparison with gene expression arrays" (John Marioni 2008).
In the results it states
"By these criteria, 40% of reads mapped uniquely to a genomic location, and of these, 65% mapped to autosomal or sex chromosomes (the remainder mapped almost exclusively to mitochondrial DNA)."
I couldn't help but notice the "almost exclusively to mitochondrial DNA". Almost exclusively? Can DNA be found in places other than chromosones or mitochondria? Perhaps I'm interpreting the sentence wrong. Any pointers would be appreciated
Thanks In plants, chloroplasts and other plastids contain DNA, but I suppose you are more interested in humans. Quoting from wikipedia,
In many cells cytoplasmic DNA is also found, which is different from
nuclear DNA, both in methylation levels (cytoplasmic has less), and in
sequence. EccDNA or extrachromosomal circular DNA is present in all
eukaryotic cells, derived from genomic DNA and consists of repetitive
sequences of DNA found in both coding and non-coding regions of
chromosomes. EccDNA can vary in size from less than 2000 more than
20,000 base pairs. In animals, eccDNA molecules have been shown to
contain repetitive sequences that are seen in satellite DNA, 5S
ribosomal DNA and telomere DNA. The function of eccDNA has not been widely studied, but it has been proposed that the production of elements of eccDNA from genomic DNA sequences adds to the plasticity of the eukaryotic genome and can influence genome stability, cell aging and the evolution of chromosomes
The following is multiple choice question (with options) to answer.
If you find dna floating in a cell's cytoplasm, what kind of organism is it? | [
"xerophytic",
"prokaryotic",
"eurocratic",
"unicellular"
] | B | Prokaryotic versus Eukaryotic Gene Expression To understand how gene expression is regulated, we must first understand how a gene codes for a functional protein in a cell. The process occurs in both prokaryotic and eukaryotic cells, just in slightly different manners. Prokaryotic organisms are single-celled organisms that lack a cell nucleus, and their DNA therefore floats freely in the cell cytoplasm. To synthesize a protein, the processes of transcription and translation occur almost simultaneously. When the resulting protein is no longer needed, transcription stops. As a result, the primary method to control what type of protein and how much of each protein is expressed in a prokaryotic cell is the regulation of DNA transcription. All of the subsequent steps occur automatically. When more protein is required, more transcription occurs. Therefore, in prokaryotic cells, the control of gene expression is mostly at the transcriptional level. Eukaryotic cells, in contrast, have intracellular organelles that add to their complexity. In eukaryotic cells, the DNA is contained inside the cell’s nucleus and there it is transcribed into RNA. The newly synthesized RNA is then transported out of the nucleus into the cytoplasm, where ribosomes translate the RNA into protein. The processes of transcription and translation are physically separated by the nuclear membrane; transcription occurs only within the nucleus, and translation occurs only outside the nucleus in the cytoplasm. The regulation of gene expression can occur at all stages of the process (Figure 16.2). Regulation may occur when the DNA is uncoiled and loosened from nucleosomes to bind transcription factors ( epigenetic level), when the RNA is transcribed (transcriptional level), when the RNA is processed and exported to the cytoplasm after it is transcribed ( post-transcriptional level), when the RNA is translated into protein (translational level), or after the protein has been made ( post-translational level). |
SciQ | SciQ-1401 | neuroscience, brain
When $m$ synapses simultaneously generate an EPSP of size $u$, these EPSPs will sum up at the axon hillock to
$$ U = m\times u\times 10^{-\alpha r}$$
Only if $U \geq \theta$ an action potential will be generated, that is, the minimal number of simultaneously active synapses to generate an action potential is
$$ n = 10^{\alpha r}\ \frac{\theta}{u}$$
With this we can estimate the excitability $E = \log\frac{N}{n} = \log 10^{-\alpha r}\frac{N\ u}{\theta}$ by
$$E = -\alpha r + \log(N) + \log \frac{u}{\theta} $$
$\alpha$, $u$ and $\theta$ are more physical constants (more or less the same for all types of neurons?), $r$ and $N$ depend heavily on the arbitrary geometry/morphology of the neuron (especially do longer and more strongly branched dendrites have more synapses).
My specific questions are (please feel free to answer only with "yes" or "no"):
Has the property of excitability (in the operational sense above) been investigated a) for single neurons, b) for morphological types of
neurons?
Is there an observed significant correlation between morphological type and excitability? Note that larger dendritic trees have larger
$r$ (decreasing $E$) but also larger $N$ (increasing $E$).
The following is multiple choice question (with options) to answer.
Graded potentials are temporary changes in what, the characteristics of which depend on the size of the stimuli? | [
"components voltage",
"membrane voltage",
"organic voltage",
"organism voltage"
] | B | Figure 12.25 Graded Potentials Graded potentials are temporary changes in the membrane voltage, the characteristics of which depend on the size of the stimulus. Some types of stimuli cause depolarization of the membrane, whereas others cause hyperpolarization. It depends on the specific ion channels that are activated in the cell membrane. |
SciQ | SciQ-1402 | sensation, olfaction
http://www.comeaddestrareuncane.com/blog/tag/cani-molecolari/
In the dog, the surface of the olfactory mucosa varies between 70 and 150 cm2 - in this tissue the number of olfactory receptors varies from 250 to 280 million - In 1962, Becker et al. showed that dogs are able to recognize substances in dilutions from 1/100 to 1/10.000.000.
- http://milano.corriere.it/milano/notizie/cronaca/12_febbraio_19/cani-olfatto-parere-esperto-1903358352720.shtml
Have you noticed how a dog sniffs the urine of a female "tasting it"? It is the same action that makes the viper when it follows the track of the mouse: it evertes the tongue and carries on it the odorous particles in the buccal cavity, and this organ has a function in the middle between the olfactory and gustatory ones. "Pointing dogs" is as pointing "the wild" taste the smell.
"Eat the scent", in the jargon, because savored, not only in terms of smell, the smell of the wild. The Jacobson's organ is then a second organ capable of perceiving odors, the first we've said is represented ciliated epithelium of the mucous membrane of the nose.
But there is a third organ called the "Rodolfo-Masera" which also serves to sense the emanations chemical (not yet known which), that way you could explain a specialization of these organs to perceive certain groups of biochemicals than others.
- http://www.laciotola.net/Cani/la-funzione-olfattiva-del-cane.html
The following is multiple choice question (with options) to answer.
How many different types of taste neurons does the tongue contain? | [
"five",
"ten",
"three",
"four"
] | A | Your sense of taste is controlled by sensory neurons , or nerve cells, on your tongue that sense the chemicals in food. The neurons are grouped in bundles within taste buds . Each taste bud actually has a pore that opens out to the surface of the tongue enabling molecules and ions taken into the mouth to reach the receptor cells inside. There are five different types of taste neurons on the tongue. Each type detects a different taste. The tastes are:. |
SciQ | SciQ-1403 | bacteriology
Title: Why is there an increase of diagnoses of Lyme disease? On the Center for Disease Control page for Lyme disease, you can see the progression of reported cases of Lyme disease from 2001 until 2016 and see that over time, there are more reported cases of Lyme Disease.
I am wondering if there is an actual increase in incidence or if, perhaps, there is an increased awareness of the disease causing doctors to be more likely to test for it (and diagnose it) than they were in 2001.
Is there any information supporting one or the other? One of the opinions expressed on the CDC website is that the increase of diagnosis of the Lyme disease could be accounted to expansion of ticks:
Since the late 1990s, the number of reported cases of Lyme disease in the United States has tripled and the number of counties in the northeastern and upper Midwestern United States that are considered high-risk for Lyme disease has increased by more than 300%. One explanation for this trend is that the ticks that can transmit Lyme disease have expanded their geographic range and are now being found in places they weren’t seen 20 years ago. --Rebecca Eisen, Ph.D. (source)
I have also found a report containing another possible explanation:
The following is multiple choice question (with options) to answer.
Deer ticks are vectors for the bacteria that cause what disease? | [
"lyme",
"mad cow",
"malaria",
"Dengue fever"
] | A | Deer ticks are vectors for the bacteria that cause Lyme disease. The ticks are actually very small and may go unnoticed. |
SciQ | SciQ-1404 | cell-biology, development
Title: What determines the fate of a cell with respect to differentiation? I have been reading about Townes and Holtfreter's work in 1955, in which cells are dissociated from a blastocyst in an alkaline solution then mixed together and spontaneously reaggregates based on type, so epidermal cells around the outside and neural plate cells in the middle.
I understand enough about cell adhesion to understand why the cells will seem to attract cells of their own type, but would like to know how they can initially detect what to become and where they are needed in a specialised form, without something acting like a brain telling them what to become and where to go.
If the selection from the available types is random, as I suspect, what happens to blastocysts with too much epidermal tissue or vice versa? I'm struggling to imagine how organisms like this can develop without something taking the lead and actively coordinating what goes where. Cell differentiation, cell fate and cell mapping is an interplay of accessible evolutionary strategies/programmes and responses to dynamic environmental cues such as specialized hormones (e.g. morphogens) and physical parameters and constraints. That is putting it very broadly. It is a complex issue, if L. Wolpert's PLOS assays are any indication. I compiled a few links to get you started.
Specifically, reappraising the topic of your cited classical experiment are R.Moore et al:
The classical cell sorting experiments undertaken by Townes and
Holtfreter described the intrinsic propensity of dissociated embryonic
cells to self-organize and reconcile into their original embryonic
germ layers with characteristic histotypic positioning. Steinberg
presented the differential adhesion hypothesis to explain these
patterning phenomena.....
The following is multiple choice question (with options) to answer.
What is established by the ph differences between the two sides of the blastoderm cells? | [
"dorsal-ventral axis",
"proximal axis",
"cylindrical - ventral axis",
"posterior axis"
] | A | |
SciQ | SciQ-1405 | zoology, digestive-system, pets
Title: Is it safe to feed an adult fire salamander with slime maggots? As a reminder, maggots feed of a flesh, while fire salamander consumes his prey alive, without killing it.
Can it happen that the maggot will start eating the salamander from the inside? Although I am afraid I don't know much about fire salamanders specifically, it is certainly possible for ingested fly larvae (or larvae hatching from ingested eggs) to survive ingestion and subsequently cause intestinal damage. Parasitic infestation by fly larvae that grow inside the host while feeding on its tissue is called myiasis. Enteric myiasis (also called gastric, rectal, or intestinal myiasis to indicate the affected part of the digestive system) occurs occasionally in humans following the ingestion of cheese infested with cheese fly maggots. Casu marzu, a traditionally produced Sardinian cheese, is supposed to have live cheese fly maggots in it, and cases of bloody diarrhoea following its consumption are known. If they're dead the cheese is considered unsafe to eat (although personally I'd correct that to 'more unsafe').
The following is multiple choice question (with options) to answer.
During metamorphosis, most salamander species go through what aquatic stage on the way to becoming adults? | [
"metaphase",
"anaphase",
"prophase",
"larval stage"
] | D | |
SciQ | SciQ-1406 | solvents, extraction, distillation
I don't know what part is confusing or exactly what "separation" you mean when you say "after the separation". But if you mean after the separatory funnel phase separations, then roughly the steps are:
"Drying" the DCM solvent. Even though DCM and water don't completely mix (they form two phases, which, as explained above, is the reason why it works to extract cinnamalehyde from an aqueous emulsion), some water does leach into the DCM phase during the separation. "Washing" the DCM with brine helps rid the DCM of the small amounts of water dissolved in it after the phase separation. Adding calcium chloride powder to the DCM is an even more effective drying agent that removes the last bit of water from the DCM.
DCM distillation. After drying the DCM, all the cinnamaldehyde is still dissolved in a (now "dry" or water-free) DCM phase. To get rid of the DCM and obtain the pure cinnamaldehyde oil, another simple distillation is performed. Because DCM boils at around 40 °C and cinnamaldehyde doesn't boil until 248 °C, it is fairly easy to remove nearly all the DCM by simple distillation, leaving the oil.
NMR. The very end shows a proton NMR of the oil. This is something that requires big fancy equipment and won't be possible for home chemists. Don't worry about it and enjoy your cinnamaldehyde!
The following is multiple choice question (with options) to answer.
What is a purification process where the components of a liquid mixture are vaporized and then condensed and isolated? | [
"distillation",
"conduction",
"dispersion",
"sterilization"
] | A | Distillation is an effective method to separate mixtures comprised of two or more pure liquids. Distillation is a purification process where the components of a liquid mixture are vaporized and then condensed and isolated. In simple distillation, a mixture is heated and the most volatile component vaporizes at the lowest temperature. The vapor passes through a cooled tube (a condenser), where it condenses back into its liquid state. The condensate that is collected is called distillate. |
SciQ | SciQ-1407 | 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 gas comprises about three-fourths of earth's atmosphere? | [
"hydrogen",
"oxygen",
"carbon dioxide",
"nitrogen"
] | D | Nitrogen is another common element found in living things. It is needed to form both proteins and nucleic acids such as DNA. Nitrogen gas makes up 78 percent of Earth’s atmosphere. In the nitrogen cycle, nitrogen flows back and forth between the atmosphere and living things. You can see how it happens in Figure below . Several different types of bacteria play major roles in the cycle. |
SciQ | SciQ-1408 | circulatory-system, lymphatic-system, veins
Title: How does most of lymph get back into the blood stream? (I don't mean the lymphatic system) I once read that it was because of osmotic pressure that it returns to the blood stream, by entering the venules. But why? If lymph originated as plasma how come that the solute concentration is higher in the venule? Doesn't plasma contain solutes such as salts, nutrients, oxygen, etc. ? Technically 'lymph' is used to refer to the fluid found within the lymphatic system. If it's not in the lymphatic system, it is not lymph fluid. Thus, your question is really asking about interstitial fluid or the plasma that was filtered out of blood capillaries.
The answer to your question is based on the Starling equation. Normally fluid leaves a capillary due to a net pressure that favors the interstitium. This net pressure is based on the hydrostatic pressure within the capillary being greater than the interstitial pressure of the surrounding tissues, and the oncotic pressure of the capillary (that draws fluid in) being weaker than the hydrostatic pressure of the capillary (that pushes fluid out). At the venule end of this system, the capillary oncotic pressure is stronger than the capillary hydrostatic pressure, drawing fluid back into the circulatory system.
Remember that albumin is the most important component which establishes the oncotic pressure within a vessel, and that this protein is normally NOT released out of a vessel during filtration. Thus, it passes from the capillary into its corresponding venule directly.
The following is multiple choice question (with options) to answer.
The lymphatic system helps return fluid that leaks from the blood vessels back to what system? | [
"cardiovascular",
"peripheral",
"pulmonary",
"nervous"
] | A | The lymphatic system helps return fluid that leaks from the blood vessels back to the cardiovascular system. |
SciQ | SciQ-1409 | waves, visible-light, electromagnetic-radiation, aether
Title: What exactly is a wave? What are waves, specifically light waves made of? Do points in a wave move along with the wave?
I was reading this post and I have become utterly confused with the concept of a wave. First, is a wave made up of particles or not? (Then again light is said to both a wave and a particle.) I am really confused. Is a light wave a collection of photons?
Second, in that post, one person mentions "material waves". I'm assuming these are waves like water waves and waves on strings/ropes, which are really made of particles. I understand the answer in context of waves in ropes, the atoms are not moving from one point to another. In water waves the water molecules do move from one point to another, don't they?
So what are the other "non-material waves" made of? In waves particles don't have to travel. For sound waves, they oscillate back and forth with pressure changes in the air, or solid/liquid materials. For water waves, water molecules move in orbits, you can tell this because when water waves hit the shore, the water level doesn't instantly change, they don't fill the shore, so the molecules move back.
When you say material waves are 'made of' something, it's more accurate to say material waves travel through space through a material medium. The particles are transferring energy in the form of a wave.
Light waves aren't 'made of' anything, they are a pair of disturbances in electric and magnetic fields, hence their name, electro-magnetic waves. When an electric field changes, it creates a magnetic field, and when a magnetic field changes, it creates an electric field. To understand how this works, you can look into Maxwell's equations of electromagnetism, specifically, the last two.
The following is multiple choice question (with options) to answer.
Light is energy that travels in the form of what type of wave? | [
"seismic",
"electromagnetic",
"particle",
"molecular"
] | B | Light is one type of electromagnetic radiation . Light is energy that travels in the form of an electromagnetic wave. Figure below shows a diagram of an electromagnetic wave. An electromagnetic (EM) wave has two parts: an electric field and a magnetic field. The electric and magnetic fields vibrate up and down, which makes the wave. |
SciQ | SciQ-1410 | synthesis, safety, polymers, green-chemistry
They are divided into two distinct groups, with very different applications, toxicological properties, and classification, based on the number of carbon atoms in their alcohol chain.
Phthalates aren't covalently bonded to the matrix of PVC. Therefore, the lighter ones can leach relatively very easy, usually due to heat or strong solvents.
The most common phthalate is diethylhexyl phthalate(DEHP). Studies show that Americans are exposed to DEHP. DEHP is believed to cause health complications in a variety of ages.
Oh, wait: Issue 3: PVC itself! But when it degrades
PVC is known for its strong linear polymer; but when it degrades (usually due to careless use or disposal) it degrades! Degradation is excessive reduction in a plastic's average molar weight. PVC will "microcrack" when it's degraded, into macroparticles that are a big threat to the environment. These particles "soak up" POPs and afterwards are usually ingested by living things, making it a big deal of our everyday plastic pollution exposure. (as wikipedia puts it)
What should I do now?! Panic?
Considering the advancement of technology and our anxiety to preserve our health we humans aren't sitting around to watch ourselves getting sick! I don't mean the hard-to-come-by sites that say overexposure to PVC isn't carcinogenic, but real efforts into solving the problem. News has been spread that REACH attempts to authorize DEHP and two other phthalates and ban their use in specific materials. DINP is another plasticizer, approved by the EU risk assesment, that will eventually replace the former plasticizers, hopefully.
Scientific researches for over ten years have proven that the amount of exposure to the chemicals mentioned is far from dangerous in current conditions and uses. So sit back relaxed; it's true that these dangers exist, but they're not serious threats to a healthy person, at least not yet.
The following is multiple choice question (with options) to answer.
Naphthalens is a chemical which is commonly used in what? | [
"inhalers",
"fertilizers",
"shampoo",
"mothballs"
] | D | Delocalization of the electrons makes for a more stable molecule than a similar molecule that does not have delocalized electrons. Benzene is a more stable and less reactive compound than straight-chain hexenes. The sp 2 hybridization of the carbon atoms results in a planar molecule as opposed to the puckered structure of cyclohexane. Benzene rings are common in a great number of natural substances and biomolecules. The figure below shows the structural formulas for vanilla and naphthalene. Naphthalens is a chemical which is commonly used in mothballs. |
SciQ | SciQ-1411 | human-biology, endocrinology, organs
Title: Is there a blood panel lab test that measures all the hormone-producing glands? I understand that there are gland-specific hormone tests, such as:
Secretin: for the pancreas; and
Prolactin/ACTH: for the pituitary; and
PTH: for the payathyroid, etc.
However, are there any "composite" blood panels that test the "entire gamut/spectrum" of organs/glands, similar to what composite metabolic panels do for your cell counts? There are no composite tests that measure all the clinically important hormone producing glands. There are too many hormones produced by too many hormone producing cells/tissues in the body to test for all of them all at once (i.e. in a panel).
For illustrative purposes only... if you go to wikipedia they have a list of all hormones in the human body which is definitely far from complete! But it gives you an indication of just "how many" hormones there are and why testing for all of them is impossible in a panel.
Even with regard only to pancreatic hormones, there are several hormones produced (e.g. insulin, glucagon, somatostatin) that aren't necessarily a marker of the glands overall function (because they are not necessarily involved in the same function). Each of these hormones has different functions even though they are produced by the same gland.
Regardless, from a medical perspective you would never have a reason to test for all of them anyway. If you tested enough of them you'd find at least one of them that would - by chance - be abnormal.
Additionally, if you asked a handful of scientists to name fifty hormones there would be a lot of different hormones on each of their lists. The definition of hormone is vague, and we are learning more about new hormones every day. In the last decade we have learned that bile acids - chemicals predominately produced by the liver that are involved in dietary fat absorption - also act as hormones. There aren't clinical reasons to study all of these molecules just yet, but this demonstrates that it would be impossible to measure all of them all at the same time in one particular "panel".
The following is multiple choice question (with options) to answer.
What substances are secreted by specialized cells usually located in endocrine glands? | [
"acid",
"lipids",
"protein",
"hormones"
] | D | |
SciQ | SciQ-1412 | atmosphere, volcanology, geochemistry, volcanoes, ozone
crises of the past (Svenson et al. 2009), where rock salt from Siberia was heated to 275C released ozone depleting halocarbons such as methyl chloride (CH3Cl) and methyl bromide (CH3Br).
In general, considering the most common salt is sodium chloride (NaCl), once dissolved, the chloride ion (Cl-) is very reactive, and forms several ozone depleting compounds (such as the halocarbon examples above), and chlorine itself can react to 'tear apart' ozone itself, as shown in the diagram below:
The following is multiple choice question (with options) to answer.
Chlorine and bromine gases released into the atmosphere have helped damage what layer of the atmosphere? | [
"polluted layer",
"ozone layer",
"carbon layer",
"stratospheric layer"
] | B | Unfortunately, the layer of good ozone is being destroyed by air pollution. The chief culprits are chlorine and bromine gases. They are released in aerosol sprays, coolants, and other products. Loss of ozone has created an ozone hole over Antarctica. Ozone depletion results in higher levels of UV radiation reaching Earth. In humans, this increases skin cancers and eye cataracts. It also disturbs the nitrogen cycle, kills plankton, and disrupts ocean food webs. The total loss of the ozone layer would be devastating to most life. Its rate of loss has slowed with restrictions on pollutants, but it is still at risk. |
SciQ | SciQ-1413 | taxonomy, mammals, cladistics
Title: Why aren't mammals and reptiles considered amphibians? We've all heard it: birds descend from dinosaurs, so they're dinosaurs too. But this got me thinking: doesn't this mean that, for instance, all terrestrial vertebrates – including humans – are technically fish? A recent video by MinuteEarth and the Wikipedia article for "Fish" confirmed my shower thought hypothesis.
Interesting. But... all amniotes, i.e. reptiles (and, by extension, birds) and mammals, descend from amphibians, right? If so, then why aren't they considered amphibians too? Mammals and reptiles aren't considered amphibians, because amniotes are not hypothesized to descend from Amphibia. That is to say that Amphibia did not evolve into Amniota. They are sister clades (actually Reptiliomorpha in the Tree of Life tree below).
The following is multiple choice question (with options) to answer.
Which kind of vertebrates are amphibians? | [
"endothermic vertebrates",
"arachnids vertebrates",
"ectothermic vertebrates",
"enterococci vertebrates"
] | C | Like fish, amphibians are ectothermic vertebrates. They belong to the class Amphibia. There are three orders:. |
SciQ | SciQ-1414 | volcanoes, pyroclastic-flows
Edit: In a research* it is suggested that a turbidite current can flow over barriers, if the thickness of the flow exceeds %65 of the barrier. One may interpret this that, after a pyroclastic current dives to shallow water it may come back to the surface again.
The following is multiple choice question (with options) to answer.
What type of forces are involved when deposited rock forms deltas or barrier islands? | [
"matter forces",
"accumulation forces",
"constructive forces",
"gravity forces"
] | C | Rivers and streams flow across continents. They cut away at rock, forming river valleys ( Figure below ). These are destructive forces. The bits and pieces of rock carried by rivers are deposited where rivers meet the oceans. These can form deltas, like the Mississippi River delta. They can also form barrier islands, like Padre Island in Texas. Rivers bring sand to the shore, which forms our beaches. These are constructive forces. |
SciQ | SciQ-1415 | ichthyology, vertebrates
Title: If an organism is supported only by cartilage, does it have an endoskeleton? Lamprey and sharks lack bones, but does this mean they are not classified as having an endoskelton? Does an organism need bone to be considered as having an endoskeleton? From wikipedia
An endoskeleton (From Greek ἔνδον, éndon = "within", "inner" + σκελετός, skeletos = "skeleton") is an internal support structure of an animal, composed of mineralized tissue.
Cartilage is a mineralized tissue so it counts as a skeleton from this definition. A bit further in the wikipedia article it says
The vertebrate endoskeleton is basically made up of two types of tissues (bone and cartilage)
The following is multiple choice question (with options) to answer.
Vertebrates differ from invertebrates because they lack this? | [
"backbone or a spinal column",
"legs",
"head",
"neck"
] | A | The first vertebrates evolved about 550 million years ago. The evolution of amphibians, reptiles, mammals, and birds occurred over the next 400 million years. The first vertebrates were ectotherms; endothermy evolved later. Modern fish, amphibians, and reptiles are ectotherms. Modern birds and mammals are endotherms. |
SciQ | SciQ-1416 | dna, zoology, radiation, entomology
1.-3. Therefore, the only sensitive part of insects is the intestinal epithelium which gets renewed on a regular basis (similar to that of humans, also a known target of radiation), but...
Insects (and generally the arthropodes) are known to have exoskeleton. This potentially serves as a good "armor" for vulnerable intestine cells, filtering out the most heavy particles (like alpha- and in some respect also the beta-particles).
EDIT: This seems not to be real protection, see the discussion in comments.
Therefore it is not a surprise that insects generally show much higher resistance against radiation.
EDIT:
As it was correctly added in the comments, there are also gamets, that are most sensitive to radiation (because they bear only the half of the normal genetic information and cannot repair mutations). Even though the lesions in gamets do not lead to immediate death, the potential sterility can easily cause the extinction.
However, cockroaches (and insects generally) are known to be r-animals, meaning that they favor the quantity (r) over quality (K) of their off-spring. This strategy is optimal when dealing with radiation-induced changes in gametes: the high number of offsprings compensates for the genetic imperfections in gametes.
[a] -- meaning that is has secreted peptides in their hemolymph that protect them
[b] -- there are phagocytes, somewhat similar to tissue magrophages in humans, but the rest of the cell chains in immune response in vertrebrates, like T- and B-cells, are completely missing. Those are responsible for the mediation and amplification of the immune response in vertebrates and are the cells that are most susceptible to radiation damage.
The following is multiple choice question (with options) to answer.
The fluid surrounding cells is hemolymph in insects and other animals with an open type of what system? | [
"circulatory",
"pulmonary",
"lymphatic",
"vascular"
] | A | |
SciQ | SciQ-1417 | organic-chemistry
Title: Iodoform reaction of alkyl halide? I read from a source that 2-iodopropane undergoes iodoform reaction. What reaction mechanism is undergone here, and why does this happen? Yes, Aaron.
It will.
Because Iodide is very good leaving group. In iodoform test, we use base... which will convert 2-iodopropane into propan-2-ol. The latter will give haloform the same way as ethyl alcohol and any other methyl ketone does!
The following is multiple choice question (with options) to answer.
Whan an alkene is aquired by an alkyl halide in an organic reaction, what kind of reaction is this? | [
"subtraction",
"extinction",
"migration",
"elimination"
] | D | When an alkene is acquired by an alkyl halide during an organic reaction. An example of elimination reaction. |
SciQ | SciQ-1418 | human-biology, food, lungs
Title: What happens to the food you accidentally aspire? I'm well aware of the health effects of aspirating solid food and liquids, but I'm interested in the reaction of the body on the biological level to the strange body on our lungs.
After I almost aspirated corn, I started to wander: what does the body do when food got on our lungs?
Will it be eventually absorbed? Destroyed by our white cells? Or just lie there forever until it fully decomposes?
The body has mechanisms to prevent food to get into the lungs, so the body is aware that eventually some food will get into the lungs. As a result, it makes sense to believe that our body would have a mechanism to deal with such issue if all other mechanisms fail ( coughing and etc.,) yet I couldn't find anything on Google. People can drown because of aspired food. If they don't then it can cause diseases, for example pneumonia. In extreme cases a tree can grow in the lungs. There are other aspiration/inhalation related diseases like silicosis or asbestos lung cancer. So it depends on the composition of the object (or liquid or powder) and other factors whether it causes a disease or not. I did not find anything about what exactly happens with these objects in the lungs. Probably the lung tries to get rid of them mechanically, if there is no success in that, then they cause a local inflammation, which can lead to diseases if it becomes chronic and/or the object contains pathogens.
Common presenting symptoms (information available in 36 cases)
included dyspnea (14), fever (9), and cough (6). A history of
recurrent pneumonia was present in 9.
2007 - Pulmonary Disease due to Aspiration of Food and Other Particulate Matter: A Clinicopathologic Study of 59 Cases Diagnosed on Biopsy or Resection Specimens
The annual overall inpatient cost associated with pediatric bronchial
foreign-body aspiration is approximately $12.8 million. Combined, the
rate of death or anoxic brain injury associated with pediatric foreign
body is approximately 4%.
2014 - The national cost burden of bronchial foreign body aspiration in children
The following is multiple choice question (with options) to answer.
What is the process by which undigested food leaves the body? | [
"peristalsis",
"digestion",
"glycolysis",
"egestion"
] | D | |
SciQ | SciQ-1419 | thermodynamics, mixtures
As the temperature increases the enthalpy increases as does T$\Delta S$, but $\Delta G$ remains largely constant and remains positive, see sketch below. This suggest that water and oil will not easily mix.
The following is multiple choice question (with options) to answer.
Because of its composition, oil does not do what in water? | [
"explode",
"separate",
"dissolve",
"form"
] | C | |
SciQ | SciQ-1420 | genetic-linkage, crossover
Figure 1.
Basically, the closer two loci are, the less likely it is that there will be a crossover between them. So if you compare three loci, two of which (A, B) are close when the third (C) is far away, you will see few AxB crossovers/recombinants but many AxC and AxB crossovers/recombinants. This is because the probability of crossovers is fairly uniform across the genome. The more distance, the more opportunities for crossover.
Another confusing feature is that the maximum number of recombinants (usually) is 50%, because at that point the two loci are assorting independently, e.g. completely unlinked and behave as if they are on different chromosomes. However, two loci can be "unlinked" and still be on the same chromosome, they are just quite far apart then.
This is not really changed by multiple crossovers. The same principle of "loci further away" --> "weaker linkage between loci" is the same no matter how many crossovers occur in a chromosome. More crossovers just means that the map is "expanded", because everything is more weakly linked than with fewer crossovers per chromosome.
Update:
It may help to be very specific about what we mean by "same chromosome" vs. "different chromosomes". Recombination happens between two molecules that can be considered the "same chromosome" even if they are different molecules. We call them "homologous chromosomes" because they pair and recombine. On the other hand, when we talk about 23 chromosomes in human cells, those are "different chromosomes", but they are actually 23 pairs of homologous chromosomes, so there are in total 46 chromosome molecules, which can be arranged in 23 homologous pairs. For each pair, we get one from each parent ("paternal" and maternal").
Recombination only occurs between homologous chromosomes.
So when recombination happens, the locus doesn't transfer to a different chromosome. It stays on the "same" chromosome, it's just a different version of the same chromosome. See this image (Figure 2):
The following is multiple choice question (with options) to answer.
Linked genes are located on the same what? | [
"chromosome",
"nucleolus",
"genome",
"bacterium"
] | A | Genes that are located on the same chromosome are called linked genes . Alleles for these genes tend to segregate together during meiosis, unless they are separated by crossing-over. Crossing-over occurs when two homologous chromosomes exchange genetic material during meiosis I. The closer together two genes are on a chromosome, the less likely their alleles will be separated by crossing-over. At the following link, you can watch an animation showing how genes on the same chromosome may be separated by crossing-over: http://www. biostudio. com/d_%20Meiotic%20Recombination%20Between%20Linked%20Genes. htm . |
SciQ | SciQ-1421 | human-anatomy, muscles
Title: Contracting muscles in humans I study biology at school, and unfortunately for me, my program skips the muscles in humans chapter.
I know (and mainly, feel) that the movement in one direction isn't created by the same muscle as the movement in the opposite direction, e.g the Triceps ("front") and Biceps ("back").
I know that the triceps straightens the elbow, while the biceps contracts the elbow.
I also know that, instead of actually moving the arm, I can contract these two muscles (when I show off, for example...) without actually moving the arm. That area becomes hard. Both muscles, as I feel, are contracting. I cannot statically contract only one of them.
My question is whether this action is something "special", or simply both muscles working against each other, resulting in zero movement? The situation you are describing where muscles are situated on opposites sides of a joint and produce opposing movements is called "antagonism." Most joints are set up where one or more muscles on either sides will produce such movements (e.g., flexors vs. extensors). Here's a question about muscles without antagonists.
When you contract all the muscles crossing a joint (i.e., when you are "showing off"), the muscles balance each other. If not, the bones would move and the joint angles would change. So taking the elbow as an example, in the image below, Arnold is contracting the elbow flexors (biceps brachii, brachialis) as well as the elbow extensors (triceps brachii). In order for the bones to remain static, the forces must be equal and opposite.
The following is multiple choice question (with options) to answer.
What move the body by contracting against the skeleton? | [
"tissues",
"hormones",
"muscles",
"nerves"
] | C | Muscles move the body by contracting against the skeleton. |
SciQ | SciQ-1422 | fluid-dynamics, pressure, flow
Title: How to calculate pumping pressure for backfilling of a borehole? I am trying to calculate the pumping pressure needed to backfill a borehole with geothermal grout. The hose is pulled up at the same rate as the borehole fills, so pumping pressure will get lower as the hole is filled. The borehole is initially filled with water and is filled bottom to top.
The way I am calculating it now is like this:
With:
Pb: pressure at B (start of the hose going into the borehole).
i: Percentage of the borehole filled with grout).
ρ: Density.
g: acceleration due to gravity.
y: depth of the borehole.
τw: friction loss from hosewall.
D: diameter of the hose.
f: Friction coefficient.
vg: velocity of the grout in the hose.
Problem is: I don't know if this is correct. Can somebody validate this or come with the right way to calculate this? A force balance on the grout column gives $$P_B+\rho_{grout}gy(1-i)-P_A-4\frac{\tau_w y}{D}=0$$This neglects any acceleration of the grout fluid and any drag caused by the upward motion of the hose. For the water, the force balance is $$P_A=\rho_{water}gy(1-i)$$ So, $$p_B=-(\rho_{grout}-\rho_{water})gy(1-i)+4\frac{\tau_w y}{D}$$So the density difference between the grout and the water reduces the pressure at B, and the grout fluid drag flow increases the pressure at B.
The following is multiple choice question (with options) to answer.
In what energy industry process are fluids pumped through a borehole, creating fractures in the rock that contains the natural gas? | [
"fracking",
"strip mining",
"grinding",
"oil wells"
] | A | With fracking, fluids are pumped through a borehole. The fluids create fractures in the rock that contains the natural gas. Chemicals in the fluid prevent the fractures from closing. The natural gas can then be pumped to the surface. |
SciQ | SciQ-1423 | radioactivity, gamma-rays
Title: how close to radioactive material to be detected I am not expert on this but we have a project to detect radioactive material, we have found an off-the-shelf devise where its sensitivity for gamma rays starts from 20 KeV. My question is if you have very small traces of a radioactive material, how close this devise should be in order to pick any gamma ray? There are various radioactivity kinds. Take for example two kinds: alpha and gamma. While gamma are electromagnetic particles, photons, with rather big energy, it can travel a long way in open air, and even penetrate not so dense barriers like wood, glass or even concrete depending on photons energy, material structure and thickness. Of course it is absorbed in heavy metals like lead.
On the other side alpha rays are just helium nuclei. It may be very energetic but usually they get absorbed even in air in short lengths - for example 0.5 m - in practice typical alpha get absorbed after several cm ( say 10cm) but there are exceptions. But they are very dangerous as they ionise matter with high efficiency, and they will be absorbed by the skin when you are close enough to the source. Absorption means here energy transfer, so basically skin will be just burned!
Detectors usually used one or another kind of radioemission of electrons caused by radiation absorption in semiconductor or on various electrodes. After amplification, electric current of such electrons is measured.
So - what is the correct answer? It depends both on energy of the radioactivity radiation and kind of the radiation, and radioactive material you are expecting to measure, detect etc. Probably you should focus on measure of gamma or beta radiation ( electrons) as they can be detected far from the source.
The following is multiple choice question (with options) to answer.
What counter provides a sensitive means of detecting radioactivity? | [
"calorie",
"geiger",
"gravity",
"bouncy"
] | B | A Geiger counter provides a sensitive means of detecting radioactivity. A tube is filled with an inert gas, which will conduct electricity when radiation enters it. When a charged particle comes into the tube, it changes the electrical potential between the anode and the cathode. This change in potential in the tube produces a change in voltage in the electrical circuit and registers as a count. Geiger counters are fairly inexpensive and reliable, so they are useful in a wide range of applications. More complicated types of counters are also available, but are generally used in sophisticated experiments. |
SciQ | SciQ-1424 | biochemistry, molecular-biology, fat-metabolism, carbohydrates
Title: What is the source of the fat in adipose tissue? I have heard the opinion that all of it comes from de novo lipogenesis of carbohydrates, but I'm skeptical. Is there evidence either way - either that dietary fat definitely gets stored in the adipose tissue, or that it never does, and all of it is from carbohydrate transmutation? The proximal source of adipocyte lipids is mainly fatty acids from circulating lipoproteins (1) after hydrolysis by lipoprotein lipase (LPL).
LPL is activated by ApoC-II, which is present in hepatic-originating VLDL and IDL lipoprotein, but also chylomicron of direct dietary source. Insulin, secreted after meals, stimulates LPL production by adipocytes.
Thus the ultimate source of these lipids is both hepatic lipogenesis (from other substrates like glucids) and dietary fats.
Lipid transport in blood, for reference purpose (Michal G. Schomburg D., Biochemical Pathways, 2012)
The following is multiple choice question (with options) to answer.
What do stored fats provide our body with for later use? | [
"energy",
"hydrogen",
"metals",
"water"
] | A | Fats are one type of lipid. Stored fat gives your body energy to use for later. It’s like having money in a savings account: it’s there in case you need it. Stored fat also cushions and protects internal organs. In addition, it insulates the body. It helps keep you warm in cold weather. |
SciQ | SciQ-1425 | biochemistry, molecules, polymers, chemical-biology
A monomer is the simplest building block of a macromolecule with the properties of that macromolecule. They can be strung together to produce a macromolecule (usually by dehydration synthesis).
I would have no problem with these definitions if not for my teacher mentioning once that some monomers can also be macromolecules by themselves. Because some monomers of certain macromolecules- such as the monosaccharide glucose vs. the disaccharide sucrose or the polysaccharide amylose - can act on their own as an essential and functional carbohydrate, they are macromolecules by themselves.
Is this true? For example, could glucose be a macromolecule by itself?
Thanks. I can't think of an example where a biological monomer would be a macromolecule.
Definitions of macromolecule vary, usually by molecular weight or number of monomers (repeat units).
Personally, I'd go with ~1000 Dalton for a minimum, but the original definition of 1000 atoms is a good start too.
In any case, no biological monomer, including glucose will function the same as a macromolecule.
Consider starch - a macromolecule of sugars. It doesn't dissolve as quickly as simple sugar and has different physical properties.
Update
To clarify my comments.. Macromolecules or polymers are made up of monomers the way words are made up of letters. So no, a glucose molecule isn't really the same as a macromolecule, just like "R" is not a word.
Yes, macromolecules can be used to make larger assemblies like microtubules, filaments, etc., much the same way that words can form sentences and paragraphs.
In the polymer literature there's even the concept of a "macromonomer" referring to a monomer that is already large in size.
In my opinion though, the basic constituents (monomers) are still amino acids, nucleic acids, sugars, etc. These are not macromolecules.
The following is multiple choice question (with options) to answer.
What long molecules are composed of chains of units called monomers? | [
"complexes",
"drummers",
"polymers",
"microbes"
] | C | Polymers are long molecules composed of chains of units called monomers. |
SciQ | SciQ-1426 | electrostatics
Title: If the entire potential energy of the charge is lost within the circuit, what happens to the charge? This is a really confusing question for me. Suppose, there is an electric circuit. And, right near to the negative terminal of the battery, I place 3 bulbs, which would take almost all the energy of the electrons(energised charge). Now, if the charge looses all of the energy, will it not stop? But if it stops, it is still under the influence of the electric field, so it should move towards the positive terminal, and because it is in the field, it still has some potential energy.
So my question:
If what I just said is right, will the charge not have infinite energy
until it moves towards the positive terminal(because of the electric
force)? But if this is true, shouldn't infinite bulbs light up in the
circuit?
If I am wrong, then what happens to the charge when it looses its
energy? What happens to the electric field? The motion of the charges is totally unlike you setting off from home walking 10 km and feeling a little tired and slowing down and then walking another 10 km and feeling even more tired and slowing down and then walking a final 10 km and arriving home at a very slow pace, indeed just reaching your front door and stopping.
Here is a simple model of what happens.
The battery sets up an electric field inside the wires.
The mobile charge carries, the free electrons which are responsible for electrical conduction, are accelerated by this electric field and gain kinetic energy. Whilst in a bulb, any one of the three, the free electrons collide with the bound ions and give those bound ions some kinetic energy.
Then before another collision with a bound ion the free electron gains some more kinetic energy from the electric field to then give some to the next bound ion it meets.
The net effect of all this is that the free electrons have an average velocity (drift velocity) and the bound ions vibrate more, their "temperature" increases. The battery is the source of the energy which ultimately resides with the bound ions. The free electrons are just the mechanism by which the energy is transferred. Even if a free electron lost all of its kinetic energy it can then take some more from the electric field so it will never be marooned.
The following is multiple choice question (with options) to answer.
Where does an object gain or lose it's energy to during travel through a potential difference? | [
"magnetic field",
"particle field",
"wave field",
"electric field"
] | D | The energy that the object gains or loses when traveling through a potential difference is supplied (or absorbed) by the electric field --- there is nothing else there. Therefore, it follows that electric fields contain energy . |
SciQ | SciQ-1427 | biochemistry, bioenergetics
Having got those out of the way, I can now attempt to answer your question (slightly rephrased). Can a reaction in a metabolic pathway be at equilibrium?
To be extremely pedantic, if there is a flux through the pathway (net conversion of first substrate to end product) then the answer is no (Newsholme & Start, 1973, p 11). That is, if there is a flux through the pathway, ΔG' cannot be exactly zero for any individual reaction. However, reactions in a metabolic pathway may be very close to equilibrium (Newsholme & Start, 1973, chapter 1).
Let’s (once again) rephrase your question. Are there any examples of reactions in metabolic pathways that are close to equilibrium, and how can we determine this?
To again quote Newsholme & Start (1973, p11) “In a series of reactions that constitute a metabolic pathway, a few may be displaced far from equilibrium, whereas the majority of reactions may be close to equilibrium”.
So how can this be determined? One way would be to measure the ratio of products to substrates (or the ratio of product to substrate pairs) in the cell, and compare this with the equilibrium constant. Note that it is only the ratio of substrate/product pairs we are interested in, not the absolute concentrations. We might be interested in the NAD+/NADH ratio in the cell, for example.
That is, we measure the mass action ratio and compare this with the equilibrium constant.
Such measurements are fraught with difficulties, but let’s agree that they can be made. We could rapidly freeze the tissue sample to -190°C (using liquid nitrogen), for example, and then measure the ratio of metabolites. Finally, it should be pointed out that comparison of mass-action ratio with the equilibrium constant is not the only way of deducing that a reaction is near equilibrium, and agreement between alternative methods is highly desirable before any firm conclusions are drawn.
Let’s consider glycolysis as an example. It is generally agreed that the reactions catalyzed by phosphoglucoisomerase, phosphoglycerate mutase and enolase are all close to equilibrium: the mass action ratios and the equilibrium constants are about the same (see Newsholme & Start, 1973, p 98).
The following is multiple choice question (with options) to answer.
Where do biochemical reactions take place? | [
"between cells",
"outside of cells",
"inside the organisms' cells",
"in atoms"
] | C | Biochemical reactions are chemical reactions that take place inside the cells of organisms. |
SciQ | SciQ-1428 | thermodynamics, physical-chemistry, chemical-potential, combustion
Title: How to thermodynamically understand process of burning a piece of coal? Let's imagine that I have a match in hand and nugget of coal on my desk. Then I light up the match and place it for few seconds near the coal so a tiny piece of nugget catches fire.
Then another piece catches fire, then another and soon all the nugget is burnt down.
How did it happen? I gave the nugget just enough heat to burn the first piece. Where does come energy to burn the rest of nugget from? It is called combustion, and it happens in materials which have a lower energy content when their component molecules join with the oxygen in the atmosphere, than when in a solid/liquid structure. When energy is given to start the fire the piece of coal burns and releases energy with excess enough to sustain the reaction and leave heat energy for use.
Combustion is a high-temperature exothermic chemical reaction between a fuel and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke.
The following is multiple choice question (with options) to answer.
When fuel is burned, most of the energy is released in what form? | [
"humidity",
"carbon dioxide",
"heat",
"precipitation"
] | C | When fuel is burned, most of the energy is released as heat. Some of this heat can be used to do work. Heat cooks food or warms your house. Sometimes the heat is just waste heat. It still heats the environment, though. |
SciQ | SciQ-1429 | electric-circuits
Title: How to apply Kirchhoff's rules in a circuit with Voltmeter?
I was trying to apply Kirchhoff's rules to find out the reading that will be shown by voltmeter. But then, I realized that the current coming out of the voltmeter arm will be zero (assuming infinite resistance) and am stuck. What should be the right approach in this case?
My (failed)Approach:
Simulation:
I tried simulating it. Looks like the circuit is valid and Voltmeter would read 14V. This is the same result we get when we solve it through other methods. But KVL seems to not apply here or not giving this result.
Please note: this is not a homework question. I was genuinely curious with this special case (note the current flowing from + to - in the 12V). I saw questions around KVL in both Physics and EE stack sites. If this is more suitable in EE, could someone help in moving it please? I don’t have enough reps to do that myself. An ideal voltmeter has no effect on the circuit, so
Solve the circuit without the voltmeter connected.
The voltmeter measures the difference between the nodes to which it connects.
The following is multiple choice question (with options) to answer.
How are voltmeters placed in the circuit? | [
"after parallel",
"since parallel",
"not parallel",
"in parallel"
] | D | Voltmeters have high resistances and are placed in the circuit in parallel. |
SciQ | SciQ-1430 | experimental-physics, error-analysis, statistics, data-analysis
But, "does not exist" doesn't seem to me to be a very well-defined hypothesis to test:
In my understanding of frequentist hypothesis testing, tests are always designed with the intent to provide evidence against a particular hypothesis, in a very Popperian sort of epistemology. It just so happens that in a lot of the toy examples used in stats classes, and also in many real-life instances, the negation of the hypothesis one sets out to prove wrong is itself an interesting hypothesis. E.g. ACME corp hypothesizes that their ACME brand bird seed will attract >90% of roadrunners passing within 5m of a box of it. W.E. Coyote hypothesizes the negation. Either can set about gathering data to provide evidence against the hypothesis of the other, and because the hypotheses are logical negations of one another, evidence against ACME is evidence for W.E.C. and vice versa.
In the quote above, they attempt to frame one hypothesis as "yes Higgs' Boson" and it's negation as "no Higgs' Boson". It seems that if the intent is to provide evidence for "yes Higgs' Boson", then in normal frequentist methodology, one gathers evidence against "no Higgs' Boson" and can quantify that evidence into a p-value or just a number of standard errors of whatever quantity predicted by the theory we happen to be investigating. But this seems to me to be silly, since the negation of the physical model that includes the Higgs' is an infinite space of models. OTOH, this is the only context in which the "five sigma" p-value surrogate seems to make any sense.
In fact, this was my original thought when I set out Googling: the five sigma standard implies that we are gathering evidence against something, but modern physics theories seem to encompass such a breadth, and are yet so specific, that gathering evidence against their bare negation is nonsense.
The following is multiple choice question (with options) to answer.
What is an attitude of doubt about the truthfulness of claims that lack empirical evidence? | [
"speculation",
"conspiracy",
"independent variable",
"skepticism"
] | D | Skepticism is an attitude of doubt about the truthfulness of claims that lack empirical evidence. Scientific skepticism , also referred to as skeptical inquiry, questions claims based on their scientific verifiability rather than simply accepting claims based on faith or anecdotes. Scientific skepticism uses critical thinking to analyze such claims and opposes claims which lack scientific evidence. |
SciQ | SciQ-1431 | human-biology, cancer, medicine
Title: Why are only few cigarette smokers prone to cancer? It's tacit that only a few populace of smokers get cancer. What spares the others from it or what specifically cause cancer in those populace? See this Washington Post Article Cigarette smokers are most certainly prone to cancer. See Cecil Medicine, Chapter 183, on the epidemiology of cancer, exposure to tobacco is the most important environmental risk factor for cancer development, at least in the US:
Exposure to tobacco is the single largest cause of cancer in the United States... All forms of tobacco can cause cancer. Cigarette smoking causes cancer of the lip, oral cavity, nasal cavity, paranasal sinuses, pharynx (nasal, oral, and hypopharnyx), larynx, lung, esophagus (squamous cell and adenocarcinoma), stomach, colorectum, pancreas, liver, kidney (adenocarcinoma and renal pelvis), urinary bladder, uterine cervix, and myeloid leukemia.
Cancer may be identified or the cause of death in fewer smokers than might be expected, though, because smoking is an even greater risk factor for cardiovascular disease, and death due to cardiovascular disease.
Cancer is an unlikely phenomenon in an individual cell, but becomes more likely at the organism level, and even more likely over time. Though tobacco may be the most important environmental risk factor for cancer, age is actually a stronger predictor of cancer (see again, Cecil Chapter 183. Autopsy studies give us a quite remarkable example, this one shows incidental prostate cancer in nearly 60% of men over 80 who died from other causes. That figure is not out of the ordinary. Live long enough and you are likely to develop cancer.
Death due to heart disease may account for the lower than expected rates of cancer diagnoses and deaths in smokers. Nothing prevents cancer as well as dying from something else. And as discussed in the blog in the Washington Post you linked to, up to 2/3 of smokers die from smoking related causes
The following is multiple choice question (with options) to answer.
Cardiovascular disease, some types of cancer, type 2 diabetes, and obesity are considered what kind of preventable diseases? | [
"age diseases",
"environmental diseases",
"lifestyle diseases",
"atmosphere diseases"
] | C | Regular physical exercise is important in preventing lifestyle diseases such as cardiovascular disease, some types of cancer, type 2 diabetes, and obesity. Regular exercise also improves the health of the muscular system. Muscles that are exercised are bigger and stronger than muscles that are not exercised. |
SciQ | SciQ-1432 | biochemistry, physiology, muscles, bioenergetics
Title: Location of t tubule in muscle Why do mammalian skeletal muscles have t-tubules at the junction of the anisotropic and isotropic band, whereas non-mammalian muscles and cardiac muscles have it at Z-line? What could have been the functional significance?
If skeletal muscle would have it at the Z-line then I think it would have been more effective in contraction of muscle fibre. So which arrangement is more efficient?
Also, why is a common arrangement (the more efficient one) not seen in all those muscle types? Interesting question. Indeed it is related to the working of cardiac muscles. First of all, lets have a look at the structure of a sarcomere of a cardiac muscle from here:
Here, what we can see is that the t-tubule is a depression formed in myocyte. It is important to know this fact here. Why? See this:
In contrast to skeletal muscle, cardiac muscle requires extracellular calcium ions for contraction to occur. Like skeletal muscle, the initiation and upshoot of the action potential in ventricular cardiomyocytes is derived from the entry of sodium ions across the sarcolemma in a regenerative process. However, an inward flux of extracellular calcium ions through L-type calcium channels sustains the depolarization of cardiac muscle cells for a longer duration. The reason for the calcium dependence is due to the mechanism of calcium-induced calcium release (CICR) from the sarcoplasmic reticulum that must occur during normal excitation-contraction (EC) coupling to cause contraction.
First, cardiac muscles don't work by external action potentials, they work on a cycle governed by themselves, known as the cardiac cell cycle.
Second, as is clear from above paragraph, these cells depend on extracellular Ca2+ ions for initiating contraction, a clear difference from skeletal muscles which need Ca2+ stored in SR. Hence, they require t-tubule at a place where a sarcomere ends. Obviously, having a depression in the middle of a sarcomere (i.e. between I- and A-band) would not work here.
Also, the structure of t-tubules is also different between the two. Compare my first image with the image below from here:
The following is multiple choice question (with options) to answer.
What process is the primary function of the branching internal tubules called protonephridia? | [
"osmoregulation",
"thermoregulation",
"enculturation",
"calcification"
] | A | |
SciQ | SciQ-1433 | universe, laws-of-physics
But if you begin with the assumption of existence of some property (pattern) of your infinite chain of balls that is independent of where you start looking at it, and show that this predicts all other local patterns with as little additional assumptions, then that “law” is more fundamental. These are called symmetries of the system.
This is something amazing about the way nature is! Some laws that we conjured up to explain local behaviour somehow can be extrapolated to understand phenomena that the laws weren’t derived from, or to make new predictions that are then observed to be true!
The following is multiple choice question (with options) to answer.
Which law means that the simplest of competing theories is most likely to be correct? | [
"Law of Conservation",
"law of parsimony",
"Newton's law",
"Murphy's Law"
] | B | The formation of scientific theories is generally guided by the law of parsimony. According to this law, the simplest of competing theories is most likely to be correct. |
SciQ | SciQ-1434 | water, metal
Title: What would be the reaction if melting iron is put in normal water? What would be the reaction if melting iron is put in normal water? Will water be chemically changed? Unlike the other metals we usually see in the reactivity series, such as calcium, magnesium, zinc, etc., hot iron does not form iron hydroxide, instead it forms iron oxide. The reaction is:
$\ce{3Fe + 4H2O <=> FeO.Fe2O3 + 4H2}$
Iron is similar to magnesium and zinc as they react only with hot water (not cold water). But the reaction of iron with hot water is less vigorous than that of magnesium and zinc.
The following is multiple choice question (with options) to answer.
Iron will do what when it is exposed to oxygen and water? | [
"rust",
"become hot",
"contract",
"expand"
] | A | Perhaps the most familiar example of corrosion is the formation of rust on iron. Iron will rust when it is exposed to oxygen and water. The main steps in the rusting of iron appear to involve the following (Figure 17.17). Once exposed to the atmosphere, iron rapidly oxidizes. anode: Fe(s) ⟶ Fe 2+(aq) + 2e −. |
SciQ | SciQ-1435 | orbit, the-moon, earth
Title: What is the distance of the Earth's orbit around the Moon? I realize the Earth and the Moon both orbit around their shared center of mass, and that in the case of the Earth and Moon this center is "inside" the Earth. However, I'm looking for an approach to determine the distance the Earth travels in one "orbit around the moon" (as small as it may be). The mass of the Earth is about 81 times that of the Moon and the distance between their centres of mass is typically 384 400 km, so the centre of mass will be about 1/82 of this distance from the centre of mass of the Earth, which is about 4700km.
The orbits are not too far from circular, so the Earth travels about $2 \pi$ times that each month, so a little under 30000km.
The following is multiple choice question (with options) to answer.
About how many days does it take the moon to make one orbit around the earth? | [
"21",
"28",
"22",
"30"
] | B | The Moon does not produce any light of its own. It only reflects light from the Sun. The Moon has phases because it orbits around Earth. One orbit takes about 28 days. As the moon moves around Earth, different parts of it appear to be lit up by the Sun. The Moon sometimes appears fully lit and sometimes completely dark. Sometimes it is partially lit. The different appearances of the Moon are referred to as phases of the Moon ( Figure below ). |
SciQ | SciQ-1436 | telescope, amateur-observing, diy
Title: Challenges when trying to build a telescope using two lenses I have some lenses - a 10 cm and 7 cm convex lense and a 4 cm and 1 cm concave lenses. I am trying to make a telescope by combining one of convex and concave lenses, but I am struggeling to do so. The picture that is created using these two lenses doesn't show anything other than the thing that can be seen by eyes. Is it possible to make simple telescope using these lenses?
PS: All of numbers are lense diameters. Diameter is important, but if you're trying to get any magnification out of that system, you need to look at the focal length.
If you have a very distant light source, like the Sun, focused through a convex lens, until the image of the source is as small and as clear as possible, then the focal length is the distance between the lens and the image you're creating. Like when you burn paper with the lens, focal length is the lens-paper distance.
For concave lenses focal length is a little more tricky to define, but they do have a focal length anyway.
If F is the focal length of the forward lens (the objective), and f is the focal length of the lens near your eye (the ocular, or the eyepiece), then the magnification of the instrument is:
M = F / f
So you need an objective with a long focal length, and an eyepiece with a short focal length.
Both the objective and the eyepiece could be convex actually. It's just that the image will be reversed. If the eyepiece is concave, the image will be straight-up, but the field of view of the telescope will be narrow (like looking through a peephole).
If you use both convex lenses, the distance between them need to be close to the sum of their focal lengths, F + f. Start there and adjust it slightly for best results.
If you use a concave lens for the eyepiece, then the distance between lenses needs to be the difference of their focal lengths, F - f.
The following is multiple choice question (with options) to answer.
The most common two-lens telescope, like the simple microscope, uses lenses of what shape? | [
"angular",
"convex",
"cylindrical",
"concave"
] | B | The most common two-lens telescope, like the simple microscope, uses two convex lenses and is shown in Figure 26.23(b). The object is so far away from the telescope that it is essentially at infinity compared with the focal lengths of the lenses ( d o ≈ ∞ ). The first image is thus produced at. |
SciQ | SciQ-1437 | human-biology, biochemistry, metabolism, food
Absorption in the gut is different for glucose and fructose, as is transport into cells.
Both glucose and fructose are (or can be) metabolised to pyruvate. However fructose is first metabolised to fructose 1-phosphate, and only enters glycolysis at the triose phosphate stage. A consequence of this is that it by-passes any regulation that occurs for the metabolism of glucose after conversion to glucose 6-phosphate. (In addition, glucose 6-phosphate has alternative metabolic possibilities not shown).
Postscript
This provides the framework for considerations of the consequences of dietary intake of sucrose, which are not part of the question and off-topic here, as already mentioned. Despite that, this topic has been addressed in questions in SE Biology, as well as elsewhere on the internet. I try not to offer advice to others (nor to take it from strangers). However my wife, whose advice I am sometimes obliged to take, professes the following:
“All things in moderation, and moderation in all things.”
The following is multiple choice question (with options) to answer.
Glucose, galactose, and fructose are all what? | [
"alucoxes",
"hexoses",
"fluxes",
"structoxes"
] | B | Figure 3.5 Glucose, galactose, and fructose are all hexoses. They are structural isomers, meaning they have the same chemical formula (C6H12O6) but a different arrangement of atoms. |
SciQ | SciQ-1438 | mass, measurements
Title: How precise can current technologies measure the mass of an object? Masses of various objects are listed on this wikipedia page: Orders of magnitude (mass). For example, mass of an HIV-1 virus is on the order of 1 femtogram.
Are these data actually measured (which I really doubt), or calculated?
What is the most precise measurement technique we have to measure the mass of an object? The most precise measurement of the mass of an electron was reported by Sturm et al in Nature 506, 467–470 (27 February 2014), quoting a relative precision of $3\times 10^{-11}$, meaning they determined the mass to better than $3\times 10^{-41}~\rm{kg}$.
If that is not the best, at least it gives you an upper bound...
Note that if you could weigh such a small mass directly with scales on earth, the force would be equivalent to the gravitational pull of a mosquito (mass 2.5 mg) on a grain of sand (0.7 mg) at a distance of about 6 million kilometers - about 17 times the distance to the moon...
Astonishing.
Acknowledgement: CuriousOne's comment got me thinking about the measurement of the mass of the electron, and led me to the above analysis.
The following is multiple choice question (with options) to answer.
Which property can you study by comparing the mass of an object relative to its size? | [
"density",
"motion",
"weight",
"volume"
] | A | A golf ball and a table tennis ball are about the same size. However, the golf ball is much heavier than the table tennis ball. Now imagine a similar size ball made out of lead. That would be very heavy indeed! What are we comparing? By comparing the mass of an object relative to its size, we are studying a property called density. Density is the ratio of the mass of an object to its volume. |
SciQ | SciQ-1439 | organic-chemistry, stoichiometry
Title: What is mol % and how do you calculate the mass of a compound needed to be a certain mol % relative to another compound at a particular volume? I know that there is some stoichiometry involved, but I am lost here. I know you need the molecular weight of both compounds and that's about it? Assuming we have a binary mixture, or equivalently, a mixture that only involves two different components $A$ and $B$, the total mass of the mixture is simply the sum of the individual masses:
$$m=m_A+m_B$$
The same logic applies to the total amount of the mixture:
$$n=n_A+n_B$$
When you divide the mass of $A$ and $B$ (separately) by the total mass of the mixture, you obtain the mass fraction of $A$ and $B$ in the mixture:
$$X_A=\frac{m_A}{m}\quad\quad X_B=\frac{m_B}{m}$$
When you divide the amount of $A$ and $B$ (separately) by the total amount of the mixture, you obtain the mole fraction of $A$ and $B$ in the mixture:
$$Y_A=\frac{n_A}{n}\quad\quad Y_B=\frac{n_B}{n}$$
In a binary mixture, the sum of fractions of $A$ and $B$ is equal to 1:
$$X_A+X_B=1$$
$$Y_A+Y_B=1$$
The molar mass of a binary mixture can be calculated with either the mass fractions or mole fractions, and the molar masses of each component:
$$M=\left(\frac{X_A}{M_A}+\frac{X_B}{M_B}\right)^{-1}$$
$$M=Y_A\;M_A+Y_B\;M_B$$
Finally, if you want to convert a mass fraction into a mole fraction or vice-versa, you can use these formulas:
The following is multiple choice question (with options) to answer.
What term means the percent by mass of each element in a compound? | [
"percent composition",
"molecular composition",
"calculated composition",
"mass composition"
] | A | Chemists often need to know what elements are present in a compound and in what percentage. The percent composition is the percent by mass of each element in a compound. It is calculated in a similar way that we just indicated for the peanut butter. |
SciQ | SciQ-1440 | physical-chemistry, thermodynamics, gas-laws, phase-diagram
If you want to be creative, such as $T_\mathrm{r} \equiv T / \sqrt{T_\mathrm{c}T_\mathrm{t}}$, where $T_\mathrm{t}$ is the triple temperature, this won't work. $T_\mathrm{t}$ will be in some part of the equation, and we will have to say that "all fluids at the same reduced temperature, reduced volume, and triple temperature will lead to the same deviation from ideality". This is not the statement of the theorem, because it adds one more thing. You are left with no other choice.
The following is multiple choice question (with options) to answer.
The combined gas law involves three properties of a gas - volume, absolute temperature, and what? | [
"power",
"direction",
"time",
"pressure"
] | D | To this point, we have examined the relationships between any two of the variables of , , and , while the third variable is held constant. However, situations arise where all three variables change. The combined gas law expresses the relationship between the pressure, volume, and absolute temperature of a fixed amount of gas. For a combined gas law problem, only the amount of gas is held constant. |
SciQ | SciQ-1441 | electromagnetism, charge
You may ask why it is then so contrary to speak that two opposite charges cancel each other. No objection. All I want you to remember is that it is the net charge that is zero. Individually the charges are not zero. Take the example of an ionic crystal, say $NaCl$, where $Na^+$ and Cl^-$ ions are tightly held together by electrostatic attraction. Both ions have equal and opposite charges. If the interaction between the two lead to the individual destruction of charges (losing property as a charge), then how the solid continues to be so brittle. There is always interaction between the two ions. This means the interaction between the two charges do not cause the charges to lose their charge. It's the effective charge that is zero. We then speak about a system, not about individual charges.
The following is multiple choice question (with options) to answer.
What is the force of attraction that holds together positive and negative ions? | [
"electron bond",
"integral bond",
"magnetic bond",
"ionic bond"
] | D | An ionic bond is the force of attraction that holds together positive and negative ions. It forms when atoms of a metallic element give up electrons to atoms of a nonmetallic element. The Figure below shows how this happens. |
SciQ | SciQ-1442 | homework, cell-membrane, human-physiology, lungs
Title: How many cell membranes are oxygen and carbon dioxide diffuse through in the lungs? In the lungs, oxygen and carbon dioxide pass through cell membranes by diffusion.
Which row is correct?
The correct answer is D, but I think it should be B. I can only think about three layers as maximum which are; epithelium of alveolus, endothelium of capillaries and the membrane of red blood cell. I don't know what are remainings.
Any help would be much appreciated! Oxigen goes from the alveolar's lumen to the cytoplasm of the erythrocyte, and that's 5 membranes:
the "top" of the alveolar epithelial cell
the "bottom" of such cell
the "top" of the endothelial cell (capillary)
the "bottom" of such cell
the erythrocyte membrane
You got all the cells right, but your only problem was this: oxygen diffuses through the cell membrane entering the cell, moves through the cytoplasm, and diffuses through the membrane again exiting the cell. So, for each cell, you have to count 2 membranes. For the last one, the erythrocyte, you have only 1 membrane (because it is $\ce{O2}$ final destination).
For the $\ce{CO2}$ the situation is a little bit more tricky. We have the same 4 membranes (2x epithelial cell and 2x capillary), but $\ce{CO2}$ can come from 2 locations:
from the erythrocyte, where it is formed from $\ce{H2CO3}$ (by the reaction $\ce{H2CO3 -> H2O + CO2}$) or released from the N-terminal group of proteins, like haemoglobin (where it has previously bound)
from the plasma (around 9% of the $\ce{CO2}$).
In the first case we have 5 membranes, and in the second case just 4.
So, the correct answer is D.
The following is multiple choice question (with options) to answer.
In the lungs, bicarbonate is transported back into the red blood cells in exchange for what? | [
"phosphate",
"chloride",
"glucose",
"oxygen"
] | B | 39.4 Transport of Gases in Human Bodily Fluids Hemoglobin is a protein found in red blood cells that is comprised of two alpha and two beta subunits that surround an iron-containing heme group. Oxygen readily binds this heme group. The ability of oxygen to bind increases as more oxygen molecules are bound to heme. Disease states and altered conditions in the body can affect the binding ability of oxygen, and increase or decrease its ability to dissociate from hemoglobin. Carbon dioxide can be transported through the blood via three methods. It is dissolved directly in the blood, bound to plasma proteins or hemoglobin, or converted into bicarbonate. The majority of carbon dioxide is transported as part of the bicarbonate system. Carbon dioxide diffuses into red blood cells. Inside, carbonic anhydrase converts carbon dioxide into + + carbonic acid (H2CO3), which is subsequently hydrolyzed into bicarbonate (HCO− 3 ) and H . The H ion binds to hemoglobin in red blood cells, and bicarbonate is transported out of the red blood cells in exchange for a chloride ion. This is called the chloride shift. Bicarbonate leaves the red blood cells and enters the blood plasma. In the lungs, bicarbonate is transported back into the red blood cells in exchange for chloride. The H+ dissociates from hemoglobin and combines with bicarbonate to form carbonic acid with the help of carbonic anhydrase, which further catalyzes the reaction to convert carbonic acid back into carbon dioxide and water. The carbon dioxide is then expelled from the lungs. |
SciQ | SciQ-1443 | 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.
What is defined as an organism in the earliest stages of development? | [
"an embryo",
"a zygote",
"a gamete",
"an nucleus"
] | A | An embryo is an organism in the earliest stages of development. Embryos of different species may look quite similar, even when the adult forms look very different. Look at the drawings of embryos in Figure below . They represent very early life stages of a chicken, turtle, pig, and human being. The embryos look so similar that it’s hard to tell them apart. Such similarities provide evidence that all four types of animals are related. They help document that evolution has occurred. |
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