source string | id string | question string | options list | answer string | reasoning string |
|---|---|---|---|---|---|
SciQ | SciQ-6644 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
Prokaryotes divide via binary fission and do not undergo what process of cell division? | [
"mitosis",
"fusion",
"prophase",
"meiosis"
] | A | Reproduction Reproduction in prokaryotes is asexual and usually takes place by binary fission. Recall that the DNA of a prokaryote exists as a single, circular chromosome. Prokaryotes do not undergo mitosis. Rather the chromosome is replicated and the two resulting copies separate from one another, due to the growth of the cell. The prokaryote, now enlarged, is pinched inward at its equator and the two resulting cells, which are clones, separate. Binary fission does not provide an opportunity for genetic recombination or genetic diversity, but prokaryotes can share genes by three other mechanisms. |
SciQ | SciQ-6645 | visible-light, biophysics, vision
Title: Why does adding red light with blue light give purple light? Our eyes contain 3 photoreceptor cells (cones) to perceive three wavelength ranges of light. Here is a visual representation of the wavelengths by these receptors (S, M and L).
So if we have light of 440 nm, it results in the color blue. If we have light of 540 nm, it results in the color green. If we see light of 650 nm, it results in the color red.
I think I understand our ability of the brain to mix the results of the signals of these receptors, producing colors like yellow. However, what I do not understand is how the color spectrum is displayed like this:
Given that spectrum, I would suggest that the color 'blue' is actually a mix between the receptors S and M. And the pure result of activating the S-receptor would result in the color 'purple' (I would describe the color in the left of the image as purple, right). Therefore, the receptor colors should instead be RGP (red, green, purple) instead of RGB (red, green, blue).
However, there is one problem with this which I cannot explain. How come that mixing red light with blue light also results in purple light? How is it possible that purple light can be achieved through mixing (additively) blue and red light, just as going to the shortest wavelength boundary of what we can see (from blue to ultraviolet via purple)?
So the actual problem here is:
Purple is the color at the very shortest wavelength we can see.
Purple is an additive mix between what we see as red light and blue light.
The following is multiple choice question (with options) to answer.
Light with the shortest wavelength appears as what color? | [
"red",
"violet",
"blue",
"green"
] | B | The wavelength of visible light determines the color that the light appears. Light with the longest wavelength appears red, and light with the shortest wavelength appears violet. In between are the wavelengths of all the other colors of light. |
SciQ | SciQ-6646 | volcanology
Title: Does the size of Earth increase due to volcanism? In a volcanic eruption, magma rushes to the 'outside' of the Earth. Does this mean the size of Earth also increases? If not, how is the volume left after the magma rushed out refilled? This is actually a more complicated question than it seems on the surface (no pun intended). The short answer is that the volume vacated by the magma is eventually refilled by the very tectonic processes that filled it in the first place. Crust is subducted, molten, and then rises to fill magma chambers. The process goes on and on. In some cases the plate that was being subducted eventually disappears (this will happen to the Juan de Fuca plate in a few million years), and the volcanoes associated with become extinct, not dormant but extinct. But generally speaking, volcanism is an ongoing process; the Earth is constantly recycling crustal material
The following is multiple choice question (with options) to answer.
What is lava called before it reaches the surface of the earth? | [
"pyrite",
"rock",
"crust",
"magma"
] | D | Minerals form as magma or lava cools. |
SciQ | SciQ-6647 | human-anatomy, human-physiology, blood-circulation, physiology
Title: Common site for atherosclerosis My book( textbook of anatomy abdomen and lower limb 2nd edition - by vishram Singh pg.no:286) says:
Acute arterial occlusion: It is mostly caused by embolism or thrombosis. It usually occurs in the femoral artery where it gives off the profunda femoris artery.
The following is multiple choice question (with options) to answer.
What is the term for atherosclerosis of arteries that supply the heart muscle? | [
"rapid heart disease",
"coronary heart disease",
"cardiovascular disease",
"essential heart disease"
] | B | Atherosclerosis of arteries that supply the heart muscle is called coronary heart disease . This disease may or may not have symptoms, such as chest pain. As the disease progresses, there is an increased risk of heart attack. A heart attack occurs when the blood supply to part of the heart muscle is blocked and cardiac muscle fibers die. Coronary heart disease is the leading cause of death of adults in the United States. |
SciQ | SciQ-6648 | biochemistry, plant-physiology, plant-anatomy
Title: Why do plants store energy as carbohydrates and not as fats? In my introductory biology class, we are learning about biomolecules. The textbook says fats are a more efficient energy store than carbohydrates.
So my question is - why would plants store their energy as carbohydrates and not as fats, if fats are a more efficient energy store? There are quite some reasons for why plants prefer carbohydrates for energy storage rather than fats. I will reach some of them one at a time.
The following is multiple choice question (with options) to answer.
Food is chemical energy stored in what? | [
"DNA molecules",
"oxygen molecules",
"typical molecules",
"organic molecules"
] | D | Food is chemical energy stored in organic molecules. |
SciQ | SciQ-6649 | ocean, ocean-currents, tides
Physical effects, then, are likely to include direct effects on current speed, sediment, and stratification.
The obvious possible biological effect is from collisions. This is not my field, but as I understand it no effect is likely on small fish populations from collisions, although individuals may be affected. Collision risk for large animals (e.g. sharks and marine mammals) and for diving birds is a topic of active research, and is likely (especially for mammals) to depend on their behaviour around the devices. No large animal collisions have been reported on any of the prototypes undergoing testing so far.
A good review of possible effects on benthic organisms is provided by Shields et al (2011). These may include,
The following is multiple choice question (with options) to answer.
What has a bigger impact on water quality, natural events or human activity? | [
"natural events",
"water quality",
"human activity",
"all of the above"
] | C | Natural events, like storms, volcanic eruptions and earthquakes can cause major changes in water quality. But human-caused contaminants have a much greater impact on the quality of the water supply. Water is considered polluted either when it does not support a human use, like clean drinking water, or a use for other animals and plants. The overgrowth of algae, known as an algal bloom , can result from the runoff of fertilizer into bodies of water. This excess of nutrients allows the algae to grow beyond control, bring harm to the rest of the ecosystem. |
SciQ | SciQ-6650 | reaction-mechanism, quantum-chemistry
Title: Chemical reaction energy barrier width Well chemistry before the discovery of quantum world was saying:"In order for a chemical reaction to happen , reactants must have enough energy to be converted into products."I was wondering now that we have discovered quantum worlds and quantum properties and quantum effects and quantum tunneling , maybe if the energy barrier is very narrow then we dont have to add this "Activation energy" and the reactants pass through this energy barrier to create products . Tunneling can be important for any reaction where there is a proton or electron transfer involved and the electron/proton donor/acceptor are placed in a "sweet spot" that increases the importance of this over other mechanisms.
As explained here, the conditions for appreciable contribution of tunneling to a reaction mechanism are that (1) the activation barrier be large enough (otherwise tunneling is not necessary); (2) the width of the barrier (the tunneling distance) should not be too great and (3) the particle must have significant wave (delocalized) character, that is, small mass (such as a proton or electron).
The following is multiple choice question (with options) to answer.
What is the amount of energy required to begin a chemical reaction known as? | [
"decomposition energy",
"reaction energy",
"positive energy",
"activation energy"
] | D | All chemical reactions need energy to get started. Even reactions that release energy need a boost of energy in order to begin. The energy needed to start a chemical reaction is called activation energy . Activation energy is like the push a child needs to start going down a playground slide. The push gives the child enough energy to start moving, but once she starts, she keeps moving without being pushed again. Activation energy is illustrated in Figure below . |
SciQ | SciQ-6651 | human-biology, cancer
Title: Why do most breast cancers occur in women? According to Korde et al. (2010):
Male breast cancer accounts for less than 1% of all cancers in men and less than 1% of breast cancers.
This raises the question: Why do most breast cancers occur in women?
Two plausible explanations I can think of:
A male is less likely to get breast cancer for anatomical reasons (such as a smaller quantity of breast tissue, or breast tissue that is less susceptible to cancer),
Women have higher significantly levels of estrogen, which is linked to mutations that cause breast cancer (see Cavalieria et al. (2006)).
Although, I have no evidence to suggest that either of these is predominant factor. Yes, this is mostly about estrogen. Most breast cancers rely on endogenous estrogen to sustain proliferation.
Some general reading: Cancer Medicine, Chapter 18
More in-depth reading: Endogenous Hormones as a Major Factor in Human Cancer
Requested summary of mentioned readings:
First of all, there is an established link between breast cancer cell proliferation and concentration of estrogens and progesterone, which is logical, because normal breast cells divide in response to those hormones (e.g. puberty, pregnancy, even luteal phase of the menstrual cycle). Secondly, the incidence of breast cancer in women correlates with major changes in their hormonal profile - girls and elderly women (i.e. women with lower levels of sex hormones) don't get breast cancer.
Many factors, that influence the risk of developing breast cancer are in fact tightly connected to the hormones' levels. For example - early age of menarche (or, more importantly, first ovulation, because physical activity at young age disturbs ovulation AND is protective against breast cancer) and Hormone Replacement Therapy raise the risk, early age of first full-term pregnancy or any form of artificial menopause (such as preventive oophorectomy for women with mutations in BRCA1 or 2) reduce the risk.
The first table from the book chapter lists known risk and preventive factors. The review article explains the same ideas, but connects them to other types of cancer (e.g. ovarian cancer) and suggests mechanisms, which might be the cause of those risk changes.
The following is multiple choice question (with options) to answer.
Acne is a skin disturbance that typically occurs on areas of the skin that are rich in sebaceous glands (face and back). it is most common along with the onset of puberty due to association with these? | [
"digestive changes",
"hormonal changes",
"mental changes",
"thermal changes"
] | B | Acne Acne is a skin disturbance that typically occurs on areas of the skin that are rich in sebaceous glands (face and back). It is most common along with the onset of puberty due to associated hormonal changes, but can also occur in infants and continue into adulthood. Hormones, such as androgens, stimulate the release of sebum. An overproduction and accumulation of sebum along with keratin can block hair follicles. This plug is initially white. The sebum, when oxidized by exposure to air, turns black. Acne results from infection by acne-causing bacteria (Propionibacterium and Staphylococcus), which can lead to redness and potential scarring due to the natural wound healing process (Figure 5.22). |
SciQ | SciQ-6652 | electrochemistry, redox, electrons, electricity
I sent this (as well as a list of other sources that I won't quote here) to my chemistry professor and received the following reply:
The question states electrons. Period. There are no "free" electrons in a battery (there can be delocalized electrons, but that's not the question). Batteries are made of atoms. Atoms are made of protons, neutrons and electrons. As a battery is used, through the flow of electrons, electrons are lost to the environment (fyi - there is energy/electron loss, albeit small to "run" the voltmeter and even in the flow of electrons through a conducting wire). Those electrons are no longer in the battery. Thus, the battery has the same number of protons and neutrons, but less electrons. This also means more unreactive metal cations exist in a used battery.
I appreciate all your research to make a point, but hopefully you now see the answer is true. Even your physics professor agrees because there is loss/leakage. Thus, less electrons in the battery.
Story: I have a family friend, who is a full professor of electrical engineering at Caltech. She is clearly on the cutting-edge of this field. In one of our discussions, she shared displeasure in online information. She told me her grad students often cited sources that were not true. There is more to this story, but I think the point has been made. Keep it simple. Electrons are energy. They flow. That energy goes elsewhere, leaving the initial system with less energy/electrons.
The following is multiple choice question (with options) to answer.
What are the two main components in a battery? | [
"filter and a cathode",
"anode and a cathode",
"anode and a vortex",
"vortex and a cathode"
] | B | Zinc is an important component of many kinds of batteries. This metal is mined as zinc compounds, one of which is zinc carbonate. To obtain the pure metal, the ore must go through the following chemical processes:. |
SciQ | SciQ-6653 | exoplanet
It's probably possible to have volcanic eruptions even though dozens or maybe even hundreds of miles of exotic ice because the heat has to go somewhere, eventually, assing it's likely to build up over time, so either by circulation of eruption, the heat has push through at some point. This even happens on so called "dead" planets like Mars or even the Moon. Mars still has the occasional volcanic eruption, just not very often.
But water worlds certainly can have plate tectonics. There's nothing in the water that would prevent it from happening. Plate Tectonics is, as I understand it, primarily a factor of the size of the planet. Gas planets - different story, but planets with a hard surface, Earth sized, a tiny bit smaller to a fair bit but not much bigger are good candidates for plate tectonics (I think). There's some debate on how large, I think, still going on. But I remember reading that ocean/water worlds might even be more likely to have plate tectonics. Plate tectonics is definitely something we'd look for if we ever get a close enough look at other planets in different solar-systems (exoplanets).
Just my thoughts on this. Not meant to be complete or definitive.
The following is multiple choice question (with options) to answer.
Lots of volcanoes form along which boundaries? | [
"deposit plate bounderies",
"subduction plate boundaries",
"basalt plate boundaries",
"geyser plate boundaries"
] | B | Lots of volcanoes form along subduction plate boundaries. The edges of the Pacific Plate are a long subduction boundary. Lines of volcanoes can form at subduction zones on oceanic or continental crust. Japan is an example of a volcanic arc on oceanic crust. The Cascade Range and Andes Mountains are volcanic arcs on continental crust. |
SciQ | SciQ-6654 | blood-circulation, kidney
Title: Why does glomerulus don't allow white blood cells to leave? The glomerulus in nephrons are just a ball of capillaries, so why can't it allow the white blood cells to squeeze though the epithelial cells into Bowman's capsule just like the formation of tissue fluid in other capillaries by filtration? Red blood cells, White blood cells, platelets and proteins with large molecular weight cannot pass through the podocyte and fenestrations in glomerular capillary, but small molecules like water, salts and sugars are filtered out as part of urine.
As these cells and proteins are large to cross through this filter, they remain in the capillary and create osmotic pressure within the capillary. Bowman’s space has osmotic pressure approximately zero. So, only hydrostatic pressure works in this state and help in movement of fluid across the capillary wall.
Via: https://opentextbc.ca/anatomyandphysiology/chapter/25-5-physiology-of-urine-formation/
The following is multiple choice question (with options) to answer.
Which body organ filters the blood in the body and creates urine? | [
"the kidneys",
"intestines",
"the arteries",
"liver"
] | A | The kidneys help the body maintain homeostasis in several ways. They filter all the blood in the body many times each day and produce urine. They control the amount of water and dissolved substances in the blood by excreting more or less of them in urine. |
SciQ | SciQ-6655 | bond, intermolecular-forces, electronegativity, dipole, hydrogen-bond
Title: Bending of water and methanol towards a charged objects I just had a question about why does water, methanol or any other polar substances tend to bend towards the charged object.
I think it is because of a slight dipole dipole movement between the charged object and the polar substance, but not sure if that's the reason. As you state, in an electric field, a polar molecule such as methanol or water, having an uneven charge distribution, is attracted (or repelled) by an electric field. This orients the molecule, but is not primarily responsible for the attraction of the bulk substance.
An electric field causes a force on even a nonpolar molecule such as methane or sulfur, though. You can pick up powdered sulfur with a charged piece of plastic because of electrostatic induction, which moves electrons in the bulk material.
This induced charge is similar to the effect of moon (and sun) on tides, pulling the water underneath the moon more strongly than it pulls on the more distant core of the earth, and on the core more strongly than on the ocean on the opposite side of the planet, causing uneven distribution of the water. In a similar way, an external field causes an uneven distribution of charge.
The following is multiple choice question (with options) to answer.
Compared with the molecules of many other substances, molecules of water are strongly attracted to what? | [
"helium",
"nothing",
"hydrogen",
"each other"
] | D | Compared with the molecules of many other substances, molecules of water are strongly attracted to each other. How is this likely to affect the boiling point of water?. |
SciQ | SciQ-6656 | electromagnetism, electromagnetic-radiation
Title: Why do radio waves spread out while higher frequency waves travel in beams? Why is it that radio waves spread out in proportion to the square of the distance, while higher frequency electromagnetic waves, like microwaves, infrared waves, light, etc are able to propagate as beams? What fundamental property allows higher energy waves to travel differently than lower energy? Due to diffraction, wave effects become more important as the size of the wave source becomes comparable to the length of the wave. Visible light has micrometer-scale wavelengths, so a millimeter-sized light source is thousands of wavelengths across and diffraction isn't a very big deal. But radio wavelengths can be many meters, producing similar collimation for a radio "beam" would require an emitting antenna hundreds or thousands of kilometers across.
You can use the same logic to think about shadows. A hair that's less than a millimeter across can cast a well-defined shadow, while radio waves diffract around buildings. However larger objects can cast well-defined radio shadows: for instance astrophysical radio sources disappear when they are covered by the Moon or the Sun, which are both very many wavelengths across.
Note that even "collimated" light undergoes dispersion.
Any sort of focusing optical system will produce a beam waist at some finite distance from the final focusing element (mirror or lens or whatever); beyond that beam waist the intensity of the light falls off like $r^2$ just as if a light source were at that location. A perfectly collimated beam of light is prohibited by the uncertainty principle, unless the beam is infinitely wide.
The following is multiple choice question (with options) to answer.
Greater reflection off what atmospheric layer allows am radio waves to travel even farther at night than they can during the day? | [
"exosphere",
"stratosphere",
"troposphere",
"ionosphere"
] | D | A: With greater reflection off the ionosphere, AM waves can travel even farther at night than they can during the day. Radio receivers can often pick up radio broadcasts at night from cities that are hundreds of miles away. |
SciQ | SciQ-6657 | rotational-dynamics, atmospheric-science, earth
Title: Earth is rotating
Possible Duplicate:
Why does the atmosphere rotate along with the earth?
If i take off from land on a helicopter straight above the earth surface to a certain height and stay there for few mins/hours and come down.
Why am i coming down to the same place where i took off?
If the earth is rotating i should land on a different place right because i have not moved i am just coming down straight.I moved only vertically.
I got this thought because i was thinking why are we spending so many hours on flights to reach a country on west if i started from a eastern country.
May be there are a lot of scientific reasons behind this which i am not aware excuse me if it sounds silly.I thought this would be the best place to ask. The helicopter in your example would have some velocity given to it by the Earth. I believe atmospheric drag would play a significant role in this, but let's ignore that for now.
You may have heard the process of an orbit described as continuous free fall, where you fall "towards" the other body just as fast as you move along the orbit. If this hypothetical helicopter lifted off, it would just be orbiting the planet!
The following is multiple choice question (with options) to answer.
Earth spinning as air moves over its surface causes what? | [
"coriolis effect",
"seasons",
"centrifugal effect",
"axial tilt"
] | A | Earth is spinning as air moves over its surface. This causes the Coriolis effect. Winds blow on a diagonal over the surface due to Coriolis effect. From which direction do the northern trade winds blow?. |
SciQ | SciQ-6658 | inorganic-chemistry, molecular-orbital-theory, halides
Title: What does the molecular orbital scheme of beryllium chloride and hydride look like? Beryllium is a somewhat fascinating element since it is the only member of the second group that behaves somewhat non-metalish and, e.g. forms a somewhat covalent chloride and a covalent hydride.
In an answer to a different and unrelated question, I tried guessing what the bonding picture of $\ce{BeCl2}$ would be. Given the monomer’s linear shape, I was inclined to assume something that introduces a four-electron-three-centre bond, which has the nice side-advantage of allowing beryllium to contribute to bonding orbitals using its s orbital only. However, I would guess that the more traditional picture would include two $\mathrm{sp^2}$ type bonds to the neighbouring chlorines and then a nonzero amount of π backbonding making the MO similar to that of $\ce{CO2}$.
What does the actual, calculated MO scheme of $\ce{BeCl2}$ look like; what does $\ce{BeH2}$’s look like, how do they compare and what can we learn from them concerning the bonding properties of beryllium? I calculated molecular orbitals for $\ce{BeCl2}$ at MP2/jun-cc-pVDZ level of theory; given below are the doubly occupied MOs at this level of theory along with their symmetry designations and energy in a.u. For some reason my Avogadro kept crashing when I tried to select an iso value I thought appropriate for the last two MOs; anyway these are completely localised $\ce{Be}$ atoms. If we look at the 8 valence orbitals, there is indeed delocalised $\pi$ bonding as you suggest, and do bear a striking resemblance to MOs for $\ce{CO2}$.
For $\ce{BeH2}$ I again ran into trouble generating nice visuals using the cube file in Avogadro. I will update this post with visuals as soon as possible (It would be great if someone can help out).
The following is multiple choice question (with options) to answer.
Beryllium hydride consists of a central beryllium atom with two single bonds to what? | [
"nitrogen atoms",
"calcium atoms",
"metabolic atoms",
"hydrogen atoms"
] | D | Beryllium hydride consists of a central beryllium atom with two single bonds to hydrogen atoms. Recall that it violates the octet rule. |
SciQ | SciQ-6659 | organic-chemistry, structural-formula, amines, identification
Title: Identify two amines I was reading a random text about the surface chemistry of YBaCuO superconductors. In the text, there was a table. The table had a list of several chemical compounds, including these two:
Alkyl Amine: FcC(O)NH(CH2)4NH2
Aryl Amine: p-Fc-C6H4-NH2
Two amines. After extensive search, I was unable to find a structural formula for it (the closest I've found was this). I even tried to draw all structural formulas I could think off in a piece of paper. But I couldn't draw a single one satisfying the second one (the easiest probably).
Can you identify these amines? What's their structural formula? The proposed strucutre of these compound are, correct me if i am wrong.
The following is multiple choice question (with options) to answer.
Amides are actually formed by bringing together an amine-containing molecule and molecule containing what? | [
"Fatty acid",
"polymer acid",
"oxidize acid",
"carboxylic acid"
] | D | Amides are actually formed by bringing together an amine-containing molecule and a carboxylic acidcontaining molecule. A molecule of H2O is lost, much like when an ester forms:. |
SciQ | SciQ-6660 | immunology
Title: Is Plasmablast a precursor of Plasma cell? I read it in Roitt's Essential Immunology.
Plasmablasts are precursor cells of short- and long-lived plasma cells and
are generally described as a proliferating fraction of
antibody-secreting cells, often found in the bloodstream
emigrating to organs such as the bone marrow.
I coudn't find any authentic source repeating the same.
Is it true? Is this book authentic enough to follow? Antigen activated B-cells enter the germinal centre dark zone to form centroblasts which undergo somatic hypermutation. These then form centrocytes in the light zone. The various possibilities/routes the centrocyte can take are shown in the following figure. If the centrocyte undergoes a class switch recombination, it becomes a plasmablast.
A plasmablast is defined as
Plasmablast
The B-cell lineage precursor of non-dividing plasma cells, which has the capacity to divide and that has migratory potential.
Once it matures as a plasma cell, it is out in the blood secreting soluble immunoglobulins or antibodies.
Another important definition to mentioned here would be of antibody secreting cells.
Antibody-secreting cells
A term that denotes both proliferating plasmablasts and non-proliferating plasma cells. The term is used when both cell types might be present
So, yes, they indeed are a precursor of plasma cells.
Also, it is necessary to clarify here that although both plasma cells and plasmablasts are antibody secreting cells, plasma cells lack membrane bound antibodies while plasmablasts retain them.
Finally, this is just the germinal centre response that is shown over here. Plasma cells and plasmablasts can also form in an extrafollicular response in extrafollicular sites in the spleen or in the medullary cords of the liver. That's another story altogether!
For a more detailed explanation, have a look at my other answer.
Image and reference: http://www.nature.com/nri/journal/v8/n1/full/nri2217.html
The following is multiple choice question (with options) to answer.
What are long living plasma cells called? | [
"memory cells",
"brain Cells",
"context cells",
"device cells"
] | A | Most plasma cells live for just a few days, but some of them live much longer. They may even survive for the lifetime of the individual. Long-living plasma cells are called memory cells. They retain a “memory” of a specific pathogen long after an infection is over. They help launch a rapid response against the pathogen if it invades the body again in the future. |
SciQ | SciQ-6661 | genetics, cell-biology, chromosome, meiosis, mitosis
https://www.khanacademy.org/science/biology/cellular-molecular-biology/meiosis/a/phases-of-meiosis
So, during metaphase I, homologue pairs—not individual
chromosomes—line up at the metaphase plate for separation.
The following is multiple choice question (with options) to answer.
When do homologous chromosomes separate and go to different gametes? | [
"during meiosis",
"before meiosis",
"during electrolysis",
"after meiosis"
] | A | During meiosis, homologous chromosomes separate and go to different gametes. Thus, the two alleles for each gene also go to different gametes. At the same time, different chromosomes assort independently. As a result, alleles for different genes assort independently as well. In these ways, alleles are shuffled and recombined in each parent’s gametes. |
SciQ | SciQ-6662 | 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 type of cells are often the product of normal cells that have lost the ability to regulate the cell cycle? | [
"sick cells",
"corrosive cells",
"uncontrolled cells",
"cancerous cells"
] | D | Many cancerous cells are the products of normal cells that have lost the ability to regulate the cell cycle. The genes that encode the proteins involved in cell cycle regulation have mutations. One category of genes, called oncogenes, accelerate the cell cycle. Some cancers can be inherited, such as breast cancer (due to mutations in the BRCA1 and BRCA2 genes). Approximately five to ten percent of cancers are entirely hereditary. Other cancers are triggered by an environmental stimulus, such as through the relationship between tobacco smoke and lung cancer, or ultraviolet radiation and skin cancer. |
SciQ | SciQ-6663 | 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.
Which ductless gland releases secretions directly into surrounding tissues and fluids? | [
"endocrine gland",
"pineal gland",
"adrenal glands",
"marrow gland"
] | A | Glandular Epithelium A gland is a structure made up of one or more cells modified to synthesize and secrete chemical substances. Most glands consist of groups of epithelial cells. A gland can be classified as an endocrine gland, a ductless gland that releases secretions directly into surrounding tissues and fluids (endo- = “inside”), or an exocrine gland whose secretions leave through a duct that opens directly, or indirectly, to the external environment (exo- = “outside”). |
SciQ | SciQ-6664 | tissue
Title: What are the main differences between lab-grown tissues and natural tissues from living animals? What are the main differences between lab-grown tissues and natural tissues from living animals?
Using a biologist's classic "structure (anatomy) and function (physiology)" idea, I thought about the followings:
Structure:
It might be difficult to recreate the composition of different tissues / cells in living things precisely with artificial methods. This may lead to bad results when the tissue is used for tests of medicines and cosmetics.
Function:
Cells might not function and produce as expected (or is harder to make them function) in artificial compositions, as cells need strictly regulated environments to function correctly.
The following is multiple choice question (with options) to answer.
When different types of tissues work together to perform a unique function, what do they form? | [
"produce",
"organs",
"Brian",
"organ"
] | D | Plant Organ Systems In plants, just as in animals, similar cells working together form a tissue. When different types of tissues work together to perform a unique function, they form an organ; organs working together form organ systems. Vascular plants have two distinct organ systems: a shoot system, and a root system. The shoot system consists of two portions: the vegetative (nonreproductive) parts of the plant, such as the leaves and the stems, and the reproductive parts of the plant, which include flowers and fruits. The shoot system generally grows above ground, where it absorbs the light needed for photosynthesis. The root system, which supports the plants and absorbs water and minerals, is usually underground. Figure 30.2 shows the organ systems of a typical plant. |
SciQ | SciQ-6665 | homework-and-exercises
Title: Is geothermal energy ultimately derived from solar energy? The following question is taken from 10th class science NCERT book chapter 14th.
Most of the sources of energy we use represent stored solar energy. Which of the following is not ultimately derived from the Sun’s energy?
(a) geothermal energy (b) wind energy
(c) nuclear energy (d) bio-mass.
The answer is given as (c) nuclear energy.
I understand that the wind moves because of the uneven heating of the earth by the sun. And biomass uses solar energy for photosynthesis.
How is geothermal energy ultimately derived from the sun? It is not a correct statement:
Geothermal energy comes from the heat within the earth. The word "geothermal" comes from the Greek words geo, meaning earth," and therme, meaning "heat." People around the world use geothermal energy to produce electricity, to heat buildings and greenhouses, and for other purposes.
The earth's core lies almost 4,000 miles beneath the earth's surface. The double-layered core is made up of very hot molten iron surrounding a solid iron center. Estimates of the temperature of the core range from 5,000 to 11,000 degrees Fahrenheit (F). Heat is continuously produced within the earth by the slow decay of radioactive particles that is natural in all rock
italics mine.
Geothermal energy comes from the original energy of the matter solidifying into the sun-planetary system, ultimately from the Big Bang, and from continuous nuclear decays and reactions .
The following is multiple choice question (with options) to answer.
Over 90% of the energy we use comes originally from what? | [
"water",
"horizon",
"earth",
"sun"
] | D | Over 90% of the energy we use comes originally from the sun. Every day, the sun provides the earth with almost 10,000 times the amount of energy necessary to meet all of the world’s energy needs for that day. Our challenge is to find ways to convert and store incoming solar energy so that it can be used in reactions or chemical processes that are both convenient and nonpolluting. Plants and many bacteria capture solar energy through photosynthesis. We release the energy stored in plants when we burn wood or plant products such as ethanol. We also use this energy to fuel our bodies by eating food that comes directly from plants or from animals that got their energy by eating plants. Burning coal and petroleum also releases stored solar energy: These fuels are fossilized plant and animal matter. This chapter will introduce the basic ideas of an important area of science concerned with the amount of heat absorbed or released during chemical and physical changes—an area called thermochemistry. The concepts introduced in this chapter are widely used in almost all scientific and technical fields. Food scientists use them to determine the energy content of foods. Biologists study the energetics of living organisms, such as the metabolic combustion of sugar into carbon dioxide and water. The oil, gas, and transportation industries, renewable energy providers, and many others endeavor to find better methods to produce energy for our commercial and personal needs. Engineers strive to improve energy efficiency, find better ways to heat and cool our homes, refrigerate our food and drinks, and meet the energy and cooling needs of computers and electronics, among other applications. Understanding thermochemical. |
SciQ | SciQ-6666 | optics, visible-light, reflection, refraction, geometric-optics
Title: Image formation at surface of water Consider a lake full of water which has an object immersed in it. Now, if an observer was at the surface at a sufficient distance so that the light ray from the object is internally reflected, would he be able to see the object? If not, then why?
Conversely, would the fish see the observer (since the visibility is constrained to a small area)? Let's draw an image to show the observer above the lake looking at an object in the lake:
where the angles $i$ and $r$ are given by Snell's law. You say:
Now, if an observer was at the surface at a sufficient distance so that the light ray from the object is internally reflected
but there is no position for the observer where they cannot see the fish and likewise the fish can always see the observer. All that happens is that as the distance between the observer and fish increases, so the angle $i \rightarrow \pi/2$, to the observer the fish appears to be nearer and nearer to the surface. This is the well known phenomenon of water appearing to be shallower than it really is.
From the fishes point of view all the light from above the water is compressed into a cone of half angle equal to the critial angle. At values of $r$ greater than the critical angle the fish sees a reflection of the lake bottom.
The following is multiple choice question (with options) to answer.
What term is used to describe an illusion that light from faraway objects is reflected by a pool of water that is not really there? | [
"version",
"Mirror",
"prototype",
"mirage"
] | D | The most common type of mirage is an illusion that light from faraway objects is reflected by a pool of water that is not really there. Mirages are generally observed in deserts, when there is a hot layer of air near the ground. Given that the refractive index of air is lower for air at higher temperatures, explain how mirages can be formed. |
SciQ | SciQ-6667 | osmosis, prokaryotes
Title: Does osmosis take place in prokaryotic cells? As far as I know, osmosis occurs in Eukaryotic cells, and I'm wondering if it could take place in prokaryotic cells too. Osmosis works across every cell membrane along a concentration gradient as its a physico-chemical principle. Water can cross the membrane (or cell wall), while the substance dissolved in it (for example salts) can not. Because eukaryotic cells only have a cell membrane, they will burst eventually, while bacteria (and also plant cells) have a more rigid cell wall, which will mostly prevent bursting. However the influx (or outflux) of water creates a pressure which is called turgor pressure. How this works is shown below (figure from here), bacterial cells and plant cells work pretty much the same way:
The following is multiple choice question (with options) to answer.
How do prokaryotes reproduce? | [
"sexually",
"asexually",
"inorganically",
"unusually"
] | B | |
SciQ | SciQ-6668 | biochemistry, gas-laws
Title: What is the state of aggregation (gas, liquid) of oxygen in blood? Atmospheric oxygen is in O2 and a gas. Then we inhale the air, our efficient lungs do the magic to filter out the oxygen and push them into the blood stream.
When we say hemo and globin transport the oxygen using the iron ions. In what state oxygen is transported in the blood? as a gas or a liquid or an ion? It is hard for me to conceive of the idea that oxygen would be in gaseous form in the blood. "GAS in blood?" e.g. Arterial Blood Gas Test
Also, how does the lungs convert the gas into something that is compatible to be in blood?
References:
Amount of Oxygen in the Blood Regarding the state of oxygen in blood: It is in solution in the blood plasma (which mostly consists of water), in the form of single molecules. Think of water which you leave exposed to air: carbon dioxide will be captured and dissolved (along with the other gases in air), but these molecules are not gaseous or liquid, but rather "in solution", which is different from the "classical" states.
Back to oxygen: As your reference already states, most of the oxygen in solution will bind to hemoglobin. The actual state of oxygen in that complex has been debated, but it is believed to be reduced by the hemoglobin iron to the superoxide anion, coordinated to Fe$^{3+}$. See Wikipedia on this.
Also, the lungs do not "convert" the atmospheric oxygen to anything, they rather allow, due to their very large surface area, the quick exchange of oxygen/carbon dioxide in solution and in the air.
The following is multiple choice question (with options) to answer.
What does hemoglobin in blood carry to the cells? | [
"methane",
"carbon dioxide",
"nitrogen",
"oxygen"
] | D | Figure 39.19 The protein inside (a) red blood cells that carries oxygen to cells and carbon dioxide to the lungs is (b) hemoglobin. Hemoglobin is made up of four symmetrical subunits and four heme groups. Iron associated with the heme binds oxygen. It is the iron in hemoglobin that gives blood its red color. |
SciQ | SciQ-6669 | surface-tension
Title: What is the surface tension of liquids in space? I mean does surface tension exists in space on liquids?
Let's take an example if I have to write something using ballpen in space and space does not have gravity. Does it works because of the surface tension? Surface tension does exist "in space", which I take you to mean "without gravity". Surface tension in liquids is simply the attractive interactions between the molecules of a liquid. That exists whether there is gravity or not. I think most pens will not work well without being in the proper orientation in gravity, though. If you try using a normal ballpoint pen and write on a paper on the ceiling, you'll probably find that it won't work because gravity is pushing the ink in the wrong direction.
The following is multiple choice question (with options) to answer.
Surface tension comes from the fact that particles at the surface of a liquid do not experience interactions from all directions which leads to what on the surface? | [
"imbalance of forces",
"waves",
"degradation of forces",
"floating particles"
] | A | Surface tension comes from the fact that particles at the surface of a liquid do not experience interactions from all directions, leading to an imbalance of forces on the surface. Surface tension is responsible for several well-known behaviors of liquids, including water. Liquids with high surface tension tend to bead up when present in small amounts ( - ball-ch10_s03_f06). Surface. |
SciQ | SciQ-6670 | 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 occer? | [
"inside labs",
"inside organisms",
"outside organisms",
"in the environment"
] | B | Biochemical reactions are chemical reactions that take place inside living things. Two of the most important biochemical reactions are photosynthesis and cellular respiration. |
SciQ | SciQ-6671 | evolution, dna, natural-selection
It seems plausible to me that we (advanced life) could have a biological mechanism to "write" needed alterations into either our own DNA or our reproductive DNA over time, triggering the very specific evolutionary developments necessary to our survival without relying on random mutation.
My question:
Is this possible? Does any similar mechanism exist that we know of? If not, how can so many specific (advanced) evolutionary leaps be otherwise explained? This entire answer will be long, so read the short part first, then read the rest if you (or anyone else) is curious. Citations are included in the long section. I can include additional citations in the short section if needed.
Long Story Short
Your question touches on some common misconceptions about how the evolutionary process. Organisms don't "want" to evolve traits. Traits evolve through the biological processes of random mutation and natural selection.
Organisms do not "want" to evolve traits. (Well, OK, I'd love to evolve an extra pair of hands but that is not possible.) Natural selection works by modifying existing traits. Your turtle can stare all she wants at food out of reach but she will not evolve a longer neck. Instead, natural variation exists among neck lengths of the turtles because of variation of the genes that determine features related to overall boxy size. Those individuals with longer necks may be able to get a bit more food, live a little longer, and reproduce a little more. They will pass along their genes to their offspring, so perhaps more of their offspring will also have longer necks. Over many generations, the turtles may have somewhat longer necks.
A common misconception is that the traits of organisms are precisely adapted for a specific need. They are not, for a few reasons. First, natural selection occurs relative to the current environment. Adaptations that work well in one environment may not be so useful in another environment. Environments are rarely stable over evolutionary time so traits are subject to constant change.
Next, as mentioned above, natural selection can only work on what traits are present. While an extra set of arms would be handy, I am a tetrapod. My four appendages, along with the appendages of all other tetrapods, trace back to our common ancestor. The appendages of all tetrapods are modifications of that ancestral trait.
The following is multiple choice question (with options) to answer.
What type of behavior has the advantage of being flexible and capable of changing to suit changing conditions? | [
"learned behavior",
"saved behavior",
"inherited behavior",
"noted behavior"
] | A | Most animals are capable of learning, but animals that are more intelligent are better at learning and depend more on learned behaviors. The big advantage of learned behaviors over innate behaviors is that learned behaviors are flexible. They can be changed to suit changing conditions. |
SciQ | SciQ-6672 | collision, material-science, glass
Title: Why marbles don't shatter like a glass panel does? Both are made of the same material, not talking about the tempered glass. But I don't see marbles shatter the way glass panel does, why is that? If I could scale up the marble to the size of a car and strike a hammer on it, would it shatter? The difference is geometry, both in shape and size.
First, consider that the smaller something is, the stiffer it is in general. Take a large rubber eraser and squeeze it (in compression, not bending) and then cut it in half and squeeze again. You need double the force to get the same deflection with half the size.
Next is the shape, where something flat like a glass pane is allowed to bend which puts the most strain into the material, compared to a sphere that mostly compresses. The details here are complex, but certain shapes are stiffer and certain ones are more complaint. A sphere is exceptional at resisting loading because most of the internal stresses are compressive.
Brittle shattering occurs when the bonds between molecules in a solid break (in tension) causing a dislocation, which then loads up neighboring molecules which in turn break also. In the end, there is a runaway process of crack propagation until the object is fully cracked.
The following is multiple choice question (with options) to answer.
This process breaks rocks and other surface materials into much smaller pieces? | [
"chemical reaction",
"leaching",
"corrosion",
"weathering"
] | D | |
SciQ | SciQ-6673 | organic-chemistry, inorganic-chemistry
But then, some inorganic compounds do have carbon too, and there may even be some compounds that some call organic, and others call inorganic, like $CO_2$.
As I have felt it, in my learnings so far, it's like inorganic chemistry is the default chemistry and organic chemistry goes a step beyond.
But I don't quite grasp the difference.
What is the real semantics behind the word "organic"?
For example, we humans are made of loads of water, and that's a pretty organic thing to me. But then, water is inorganic.
Diamonds are the carbon top of the cake, and do not transmit the idea of being an "organic" thing.
Another very confusing thing are polymers, chanins of loads of carbons with other elements, in many shapes and textures. To me, a piece of "plastic" is not a very organic thing, but indeed, they are!
That brings the semantics into an even more confusing level.
And of course, there must be historical reasons for those chosen words.
Could someone please point out where this distinction comes from and why it is important?
With all my respect to science and the people who made chemistry a useful thing. This question is not about critics, it's about not knowing the facts, so of course I am the ignorant here.
Related and useful: What is the definition of organic compounds? IUPAC is the International Union of Pure and Applied Chemistry, they make recommendations on the nomenclature. IUPAC mentions that the difference between organic and inorganic is not distinct. To quote "The boundaries between ‘organic’ and ‘inorganic’ compounds are blurred." in Brief Guide to the Nomenclature of Inorganic Chemistry R. M. Hartshorn, K.-H. Hellwich, A. Yerin.
Since the terminology of organic vs. inorganic is all human classification, it is not a binary system 0 or 1. What we can say now is that traditionally, all organic compounds do contain carbon. It can come from natural sources or purely synthetic. There is no such restriction. Plastic is an organic compound because it contains a lot of carbon chains.
Note that this word organic, as used in chemistry, has nothing to with the buzz word used in marketing of organic food, organic fruits, organically grown stuff. The word organic comes from French organique designating the jugular vein, hence related to organs or living beings.
The following is multiple choice question (with options) to answer.
What is the main element in organic compounds? | [
"oxygen",
"nitrogen",
"hydrogen",
"carbon"
] | D | Carbon is the main element in organic compounds. Carbon can form stable bonds with many elements, including itself. |
SciQ | SciQ-6674 | units, si-units, metrology
Title: How units were defined? I was wondering how we humans can be sure that one meter is one meter and that one second is one second. Nowadays, except for the Kilogram, all other units are well defined using highly accurate techniques (frequency of atoms vibrations or stuff like that). But at the end all units are kind of related to each other and the definition of each unit is based on a combination of other units. There must be some viable sources that have constant measurable values that we used to define the basic units. What is those sources?
To explain more let's start with the meter. From wikipedia, the definition is: The metre is the length of the path travelled by light in vacuum during a time interval of 1/299,792,458 of a second. So here it is clear that the definition of a meter relies on the accuracy of how we define a second.
Now let's look at the second:
the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.
How is this period calculated? The sensor has probably some equations that imply transformations using other units like Kg etc...
Where does this loop stops?
EDIT:
I think I was a little bit mistaken. Not all units are directly related and there is 3 totally independent units which are : Time (second), Temperature (kelvin) and Mass (kilogram). Time and Temperature are well defined but Kilogram is still unclear. Every existing unit can be transformed into a combination of those three. It means that all units based on Kilogram are not absolute. In short, up until now, the $kg$ was arbitrary, but now people are trying to define it based on universal constants
There is a ongoing process to try and link all the units to universal constants.
This has been done already for the second (using Cesium) and the meter (using the speed of light in a vacuum)
However, the kilogram is a little less straightforward. An interesting read is SI units revision proposal.
It proposes to link the kg to the Plank constant $h$, but also to link Kelvin $K$ to the Stefan-Boltzman constant $k$ and more of these constructions.
The following is multiple choice question (with options) to answer.
What is the basic unit of matter? | [
"ions",
"atoms",
"calories",
"neutrons"
] | B | The basic unit of matter is an atom . At the center of an atom is its nucleus . Protons are positively charged particles in the nucleus. Also in the nucleus are neutrons with no electrical charge. Orbiting the nucleus are tiny electrons. Electrons are negatively charged. An atom with the same number of protons and electrons is electrically neutral. If the atom has more or less electrons to protons it is called an ion . An ion will have positive charge if it has more protons than electrons. It will have negative charge if it has more electrons than protons. |
SciQ | SciQ-6675 | pathology
Title: Are all diseases caused by organisms (microorganisms)? Are there other causes? Or is it correct to say that all diseases are in fact caused by organisms (microorganisms)? It is not correct to say that all diseases are caused by foreign organisms. Counterexamples are:
Cancer is caused by random genetic mutations in the cells of our body. The mutations can be caused by many factors such as ionizing radiation, smoking, chemical toxins etc.
Diseases such as stroke or heart attack are caused by blood clots blocking the blood flow to essential organs.
Autoimmune diseases are caused by the immune system falsely recognizing cells of the body as foreign and attacking that tissue leading to a wide variety of symptoms.
Alzheimer's disease is caused by chronic neurodegeneration, meaning that the cells in the brain die. The causes are not quite understood but as Alzheimer's usually appears late in life it is likely related to ageing. Also, it is known that some genetic defects can lead to early-onset Alzheimers.
Prion proteins can cause diseases such as Creutzfeldt–Jakob disease also known as mad-cow disease.
Hereditary diseases such as early-onset Alzheimers or ALS are cause by gene defects inherited from the parents.
Toxins can cause chronic diseases such as lead poisoning.
The list probably goes on...
Please note that the first two on the list are the most common cause of death in developed countries.
The following is multiple choice question (with options) to answer.
What theory proposes that microorganisms are the cause of many diseases? | [
"mutated theory",
"evolution theory",
"germ theory",
"malignant theory"
] | C | The germ theory proposes that microorganisms are the cause of many diseases. |
SciQ | SciQ-6676 | bond, intermolecular-forces, electronegativity, dipole, hydrogen-bond
Title: Bending of water and methanol towards a charged objects I just had a question about why does water, methanol or any other polar substances tend to bend towards the charged object.
I think it is because of a slight dipole dipole movement between the charged object and the polar substance, but not sure if that's the reason. As you state, in an electric field, a polar molecule such as methanol or water, having an uneven charge distribution, is attracted (or repelled) by an electric field. This orients the molecule, but is not primarily responsible for the attraction of the bulk substance.
An electric field causes a force on even a nonpolar molecule such as methane or sulfur, though. You can pick up powdered sulfur with a charged piece of plastic because of electrostatic induction, which moves electrons in the bulk material.
This induced charge is similar to the effect of moon (and sun) on tides, pulling the water underneath the moon more strongly than it pulls on the more distant core of the earth, and on the core more strongly than on the ocean on the opposite side of the planet, causing uneven distribution of the water. In a similar way, an external field causes an uneven distribution of charge.
The following is multiple choice question (with options) to answer.
Water is a polar compound, so its molecules are attracted to each other and form what kind of bonds? | [
"helium",
"mixed",
"hydrogen",
"carbon"
] | C | Water is a polar compound, so its molecules are attracted to each other and form hydrogen bonds. |
SciQ | SciQ-6677 | reaction-mechanism, kinetics
Title: Relating collision theory to rate of reaction I want to relate the macroscopic advancement of a reaction, the rate of the reaction, with the microscopic collisions of the molecules. This is the type I have developed so far:
$$u = A^2 \times \frac{n_1}{m^2} \times\frac{n_2}{m^2}\times \frac{(m_1u_1^2+m_2u_2^2)}{E_\mathrm{act}}\times 1/t $$
where $u$ is the rate of reaction in $\pu{mol2 sec-1}$.
$A =$ the common area of the substances
$n_1/m^2 =$ the moles per square metre of the first substance
$n_2/m^2 =$ the moles per square meter of the second substance
$u_1$ and $u_2 =$ average velocity of molecules of each substance
$E_\mathrm{act} =$ activation energy of the reaction
Now the molecules of the first substance must bump to the molecules of the second substance with the appropriate orientation. How can I add this to my type? It is interesting to see you creating your own approach. The comments above provide good responses. I would recommend looking at Buttonwoods suggestion regarding collision theory and cross-sections. However, it appears none have answered your question directly, so I will provide my response to it here.
Question: "Now the molecules of the first substance must bump to the molecules of the second substance with the appropriate orientation. How can I add this to my type?"
My Response: You recognize that orientation is important when it comes to chemical reactions. There are many ways to handle this, I will provide three short suggestions and you can consider them or use them to come up with something else.
Arrhenius (constant) approach: The pre-exponential factor, $\alpha$, in the following Arrhenius equation absorbs two important concepts of chemical reactivity - 1) the frequency of collisions, 2) the orientation of the molecules.
$$u = \alpha e^{-E_a/RT}$$
The following is multiple choice question (with options) to answer.
What is the term for a substance that causes the speed of a reaction to increase? | [
"indicate",
"catalyst",
"component",
"monite"
] | B | A catalyst is a substance that increases the speed of a reaction. Overall, a catalyst is not a reactant and is not used up, but it still affects how fast a reaction proceeds. However, a catalyst does not affect the extent or position of a reaction at equilibrium. It helps a reaction achieve equilibrium faster. |
SciQ | SciQ-6678 | optics, lenses
Title: Rays and lenses in a viewfinder An electronic camera viewfinder has a LCD screen and a combination of lenses. When looking into the viewfinder the image looks much bigger than the actual LCD though. In fact when looking from a bit further back one can only see a tiny middle part of the LCD.
I am wondering what kind of lenses create this projection when looking into the viewfinder. I am especially struggling to draw the rays.
It would be great if someone could explain or point me to another source for an explanation. My search terms have failed me so far. The lens through which you look at the viewfinder screen basically is the same thing as a magnifying glass.
I did a search for pages that explain how a magnifying glass works, and I was surprised by how little information on that subject is out there. The best I could find was this:
https://www.quora.com/Why-are-convex-lenses-called-magnifying-glass
The diagram attempts to show how, when you use a magnifier to look at a small object that is very close to your eye, the lens bends the rays so that they seem to come from a larger object that is further away.
The picture only shows two rays, both coming from one point on the object. In reality, there are infinitely many rays coming from infinitely many points, and the lens does the same thing for all of them.
The following is multiple choice question (with options) to answer.
What is it called when rays focus at different distances from the lens? | [
"constant aberration",
"carbon aberration",
"spherical aberration",
"angular aberration"
] | C | Figure 26.30 Spherical aberration is caused by rays focusing at different distances from the lens. |
SciQ | SciQ-6679 | inorganic-chemistry, alloy
Title: If alloys are homogeneous mixtures, why can't we separate their components? An alloy is a material composed of two or more metals or a metal and a nonmetal. And, they are usually formed by heating the elements to their melting points, and then cooling them, so that the components mix. Now, why doesn't this works backwards i.e. if we heat the alloy again to melting point of their constituents, and they should separate? Once the alloy has been formed the atoms from the different metals will have shared there electrons with each other and come to an equilibrium. In this state the metal atoms have formed a complex structure which has a different reactivity or properties than each individual metal did in its original form .
The following is multiple choice question (with options) to answer.
Brass and bronze are examples of what type of mixture composed of two or more elements, at least one of which is a metal? | [
"alloy",
"compound",
"metalloid",
"halloid"
] | A | An alloy is a mixture composed of two or more elements, at least one of which is a metal. You are probably familiar with some alloys such as brass and bronze. Brass is an alloy of copper and zinc. Bronze is an alloy of copper and tin. Alloys are commonly used in manufactured items because the properties of these metal mixtures are often superior to a pure metal. Bronze is harder than copper and more easily cast. Brass is very malleable and its acoustic properties make it useful for musical instruments. |
SciQ | SciQ-6680 | molecular-genetics, human-genome
Title: What sequences are between adjacent genes? The human genome has a lot of non-coding regions, which include regulatory elements, repetitive DNA, and introns. Suppose there are two adjacent genes on a chromosome, and their positions on the chromosome are, say,
For the first gene: 11,785,723 to 11,803,245 bp.
For the second gene: 11,806,096 to 11,806,143 bp. These values include their regulatory elements, promoter and introns as well.
So what sequence is present between bases 11,803,245 and 11,806,096? Are they satellite sequences? Is this non-coding, non-regulatory region 11,803,245 to 11,806,096 bp heterochromatin? No. The intergenic regions are not necessarily heterochromatin. Chromatin conformations are usually very long range and are not usually confined to a single gene. The spread of chromatin state can be prevented by insulators/boundary elements, which again are not a part of the transcribed region. The intergenic regions can also harbour distal regulatory elements such as enhancers and silencers; they can have microsatellites, transposons etc too. To know what all are there in a specific region, you can look at the different tracks in the UCSC genome browser.
In short, there can be functional and/or non-functional DNA in-between the transcribed regions.
Repeat regions need not be heterochromatinized and conversely not all heterochromatic regions consist of repeats.
The following is multiple choice question (with options) to answer.
What is a region of repetitive noncoding nucleotide sequences at each end of a chromosome? | [
"telomere",
"cytoskeleton",
"cellular",
"diploid"
] | A | Reverse transcription also occurs with retrotransposons and during telomere synthesis in eukaryotes. Retrotransposons are self-replicating segments of eukaryotic genomes that use reverse transcriptase to move from one position in the genome to another via a RNA intermediate. A telomere is a region of repetitive noncoding nucleotide sequences at each end of a chromosome. These sequences protect the end of the chromosome from deterioration or from fusion with neighboring chromosomes. Each time DNA is replicated, small segments of DNA from the ends of the chromosome is lost. Telomerase is a reverse transcriptase that uses an RNA intermediate to elongate the 3' end of DNA strands in the telomere regions after each replication cycle. |
SciQ | SciQ-6681 | inorganic-chemistry
Title: Zinc evaporation/toxicity at room temperature I have a (slightly embarrassing) question regarding zinc powder.
I have recently broken an old mercury thermometer, and read that I can handle the mercury with powdered zinc - so I've sprinkled some on my floor. Too much probably. It turned out that unfortunately the powder is then quite hard to get out of the particular material of my floor (wood). I got out as much as possible, but I think there's still some left. So now I'm wondering if there is some danger if having all that zinc laying around.
Thanks anybody for the answer :) Zinc will amalgamate with mercury, but whether that reduces the vapor pressure of mercury very much is debatable. At best, the increased volume of zinc amalgam and the ability to amalgamate with fine droplets of mercury would make it easier to clean up the mercury as amalgam.
It might be better to spread some sulfur dust (flowers of sulfur) over the area. The sulfur should react with the mercury and tie it up as sulfide, with very low vapor pressure. Sulfur powder (and possibly the HgS) might also be easier to clean up than zinc dust, because sulfur is more like ordinary dust than a dense metal dust.
BTW, I love mercury thermometers. And I hate it when I break them!
The following is multiple choice question (with options) to answer.
What is the color of mercury oxide? | [
"green",
"yellow",
"orange",
"red"
] | D | Mercury(II) oxide is a red solid. When it is heated, it decomposes into mercury metal and oxygen gas. |
SciQ | SciQ-6682 | geophysics, plate-tectonics, earth-history, continent
Title: Why Do Supercontinents Form? It would seem, on the face of it, improbable that the continental land-masses would accumulate into a single composite, yet it has happened numerous times, and is expected to again in the future.
There must likely then be some aspect of plate tectonics which favors these arrangements.
Can anyone provide an explanation?
EDIT: This is not, as I see it, a duplicate of the 'What are the causes of the supercontinent cycle?' question. This question goes to what process drives the formation of any & all supercontinent formations, which I assert should be improbable, made more improbable by their recurrence, not so much the cycle itself. The other question did not address this more fundamental aspect, or in any case receive a pertinent account of its resolution. If anyone wants to engage on this, or doesn't see the distinction, please do so in the comments or a chat. I think the mechanisms that you're looking for are subduction, paired with the "stickiness" of continental crust.
The subduction of oceanic crust under continental crust inevitably creates a net movement of crustal material toward a continental plate. Any oceanic plate that is carrying continental material will therefore always drag that continent toward the continental plate that it is subducting underneath, always resulting in eventual collision.
If an oceanic plate has subduction occurring on both sides, the ocean will inevitably narrow until it closes, thereby causing the continental plates on either side to collide.
In every case, subduction inevitably pulls continents together.
Furthermore, once continental plates collide, they have a tendency to stick together for long periods of time, increasing the likelihood that all continental material will eventually accumulate there.
The following is multiple choice question (with options) to answer.
At a convergent plate boundary, when one plate is oceanic, there are large what? | [
"earthquakes",
"lakes",
"volcanoes",
"plateaus"
] | C | At a convergent plate boundary, when one plate is oceanic, there are large volcanoes. These volcanoes are found in lines that outline the subduction zone. Earthquakes also happen in these zones. The Aleutian Islands that border southern Alaska are an island arc. In this winter image from space, the volcanoes are covered with snow. |
SciQ | SciQ-6683 | optics, visible-light, frequency
Kind of. The reflected light contains some amount of every frequency in the visible spectrum, but it will contain different amounts of different frequencies; we call the distribution of intensity among the different frequencies the reflection spectrum of the object.
Image source
Our eyes' color vision works by seeing how much the spectrum of the light overlaps with the sensitivity curves of the Red, Green and Blue cone cells in our retina. This behaviour is indeed quite similar to how a (reasonably broad-band) antenna can pick out the intensity that lies in some pre-defined range of frequencies and output a single number for that.
For more details, see e.g. the Wikipedia article on color vision.
The following is multiple choice question (with options) to answer.
What is the term for the wavelengths of light humans can see? | [
"ultraviolet light",
"radiation",
"visible light",
"distinct light"
] | C | Visible light is the wavelengths of light humans can see. |
SciQ | SciQ-6684 | electrons, charge, definition, si-units, metrology
Title: Why isn't the charge of an electron taken to be "$-1.6 \times 10^{-19}$ coulombs" Even though we refer to electrons being negatively charged, why is it that we don't write the charge as "-1.6 × 10^-19 coulombs"? We do write the charge of the electron that way. However "the elementary charge" $e$, is not the charge of the electron (in the most common convention) see the wiki on "elementary charge". The elementary charge is the magnitude of the charge of the electron, or $-1$ times the charge of the electron. Usually $q_p$ denotes the charge of a particle $p$ when you do some kind of calculation of its motion or the field it creates or whatever. So when writing the charge of the electron we often write $q_e=-e$.
I know it's not a great system. I would have preferred for the charge of the electron to be defined as positive, but it's too late.
The following is multiple choice question (with options) to answer.
What is the charge on a single electron known as? | [
"basic charge",
"elementary charge",
"fundamental charge",
"electron charge"
] | B | The charge on a single electron is and is known as the elementary charge. |
SciQ | SciQ-6685 | human-biology, physiology, endocrinology, vitamins, homeostasis
Title: Counterintuitive action of Vitamin D? Vitamin D acts in a way which to me is counterintuitive. It functionally supplemets Parathormone. It in the intestinal tract steps up calcium absorption by altering nuclear gene expression and also prevents calcium excretion in kidneys. All of this is understandable. But it also, like parathormone, steps up osteoclast action in bone (actually steps up both osteoclast and osteoblast, but the osteoclast action is increased more to result in net bone resorption). This means that Vitamin D increases blood calcium level by increasing bone resorption.
Then how does Vitamin D help in improving bone density, bone strength and prevent rickets or osteoporosis? All of these would require bone deposition rather than resorption. There are two pieces to this question:
a) How does bone resorption (movement of Ca/Phos out of bone into the blood) result in net improvement in bone structure?
Bones are constantly remodeling, primarily in response to mechanical stressors. Although you clearly already realize this, I will make it explicit: osteoblasts are the cells that create new bone; osteoclasts break down (resorb) bone.
Quoting Harrison’s Internal Medicine1:
Radioisotope studies indicate that as much as 18% of the total skeletal calcium is deposited and removed each year. Thus, bone is an active metabolizing tissue.…The cycle of bone resorption and formation is a highly orchestrated process carried out by the basic multicellular unit, which is composed of a group of osteoclasts and osteoblasts
The following is multiple choice question (with options) to answer.
What mineral that occurs in bones helps combat osteoporosis? | [
"potassium",
"iron",
"magnesium",
"calcium"
] | D | Osteoporosis is a disease in which bones lose mass and become more fragile than they should be. Osteoporosis also makes bones more likely to break. Two of the easiest ways to prevent osteoporosis are eating a healthy diet that has the right amount of calcium and vitamin D and to do some sort of weight-bearing exercise every day. Foods that are a good source of calcium include milk, yogurt, and cheese. Non-dairy sources of calcium include Chinese cabbage, kale, and broccoli. Many fruit juices, fruit drinks, tofu, and cereals have calcium added to them. It is recommended that teenagers get 1300 mg of calcium every day. For example, one cup (8 fl. oz. ) of milk provides about 300 mg of calcium, or about 30% of the daily requirement. Other sources of calcium are pictured in the Figure below . |
SciQ | SciQ-6686 | geomorphology
Title: What causes these mound-like ground formations? Whilst riding on Mam Tor in Castleton, England I came across this scene (not my photo) and I would like to know what causes the formations which I have ringed in red. They look like piles of earth have been deposited a long time ago, but clearly that can't be the case, so what causes them?
Another image of these mounds They're landslide deposits; Mam Tor gets its name, which translates as "mother hill", from the regular landslides that come off the higher slopes and form hillocks further down into the valley.
The following is multiple choice question (with options) to answer.
When the wind deposits sand, it forms small hills, what are these hills called? | [
"snow banks",
"mud puddles",
"sand tunnels",
"sand dunes"
] | D | When the wind deposits sand, it forms small hills. These hills are called sand dunes ( Figure below ). For sand dunes to form, there must be plenty of sand and wind. Sand dunes are found mainly in deserts and on beaches. |
SciQ | SciQ-6687 | hydrolysis, esters
Title: Mechanism of Acid Hydrolysis I wanted to ask a question about acid catalysed hydrolysis.
I learnt in an introductory course to Physical Organic Chemistry that there are different ways that an ester can be hydrolysed acidically:
$\ce{A_{AC}1}$
$\ce{A_{AC}2}$
$\ce{A_{AL}1}$
$\ce{A_{AL}2}$
There are different ways that esters can be hydrolysed:
– catalysis by acids (A) or bases (B)
– cleavage of acyl-oxy (AC) or alkyl-oxy (AL) bonds
– the molecularity of the key step (1 or 2).
Using Acids (A) there are 4 different ways to hydrolyse an ester using acid catalysis:
$\ce{A_{AC}1}$ Cleavage of Acyl-Oxy Bond Unimolecular
$\ce{A_{AC}2}$ Cleavage of Acyl-Oxy Bond Dimolecular
$\ce{A_{AL}1}$ Cleavage of Alkyl-Oxy Bond Unimolecular
$\ce{A_{AL}2}$ Cleavage of Alkyl-Oxy Bond Dimolecular
An explanation can be found here.
But consider this question, with the marking scheme given below:
The following is multiple choice question (with options) to answer.
Carboxylic acids have an acidic hydrogen atom, but esters do not. what do esters have in place of an acidic hydrogen atom? | [
"synthesis group",
"crystallization group",
"hydrocarbon group",
"carbonation group"
] | C | Unlike ethers, esters have a carbonyl group. Unlike carboxylic acids, esters have no acidic hydrogen atom; they have a hydrocarbon group in its place. |
SciQ | SciQ-6688 | ecology, biogeography
Edit in response to comments
Comment about biome scale
The reason behind the scale comment is that typically we observe succession for a given habitat. Part of this stems from the origin of the succession ideas, where Frederic Clements posited that climate was the major driving factor of successional trajectories (Clements 1916). This would actually fit well with the biome view of succession, however in order for this model to explain all the variation we see in the world (eg. why a tree grows in location X but not location Y 4 metres away), you devolve into splitting the world into infinitesimally small micro-climates. Henry Gleason proposed a more individualistic model, which suggested that climate was just one influence, and that each plant species responds to a myriad of different environmental cues (Gleason 1927). The sum of these responses results in the community at a given location. This seems to fit better with our current understanding of succession but is not without problems. In a Gleasonian model, any variation can be expected to result in a different community. Since it would be strange for the pampas region to be homogeneous over 1.2 million km2, there are likely distinct communities within the biome, each developing as a result of factors like soil moisture, soil chemistry, climate, wind exposure, and herbivore use. One can still talk about succession at a biome scale, but at that scale we would be thinking about what factors lead the pampas region to become a grassland, rather than what factors lead grass X, tree Y and forb Z to coexist next to each other.
Factors maintaining grassland type ecosystems are fairly uniform globally. You need some sort of event that will kill woody vegetation but not kill grasses and forbs. Fire and grazing are natural examples (Briggs et al. 2002), but mowing would also maintain grassland (Fidelis et al. 2012). Earthquakes are unlikely to maintain grassland as trees and shrubs are likely to survive earthquakes.
Comment about global pampas
The following is multiple choice question (with options) to answer.
Latitude, humidity, and elevation affect the type of what, a term for a large naturally occurring community? | [
"biome",
"ecosystem",
"territory",
"climate"
] | A | Factors affecting biome type include latitude, humidity, and elevation. |
SciQ | SciQ-6689 | waves, interference, wavelength, superposition
The wavelength is the distance of a "cycle". Take the horizontal length between any two crests, or any two troughs, and what you get is called the wavelength. In physics, this is notated with the $\lambda$ symbol (the Greek letter Lambda). In the plot above, the wavelength has a value of $\pi$.
The amplitude is the height from the centre line to either the crest or the trough.
Destructive interference happens when the squared amplitude of the sum of the waves is lower than the sum of the squared amplitudes of the waves.
Therefore, the interference between two waves is the "most destructive" when the phase difference is an odd number of half-wavelengths, as shown in the plot above with the "$\pi/2$", "$3\pi/2$", "$5\pi/2$" points on the horizontal axis.
The following is multiple choice question (with options) to answer.
The distance between two crests of a wave of light is referred to as what, which is related to the color of light? | [
"bandwidth",
"spectrum",
"wavelength",
"magnitude"
] | C | wavelength : The distance between two crests of a wave of light. The color of light is related to its wavelength. This is inversely proportional to frequency. |
SciQ | SciQ-6690 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
What is the basic unit of structure and function in all organisms? | [
"the neutron",
"the atom",
"the electron",
"the cell"
] | D | The cell is the basic unit of structure and function of all organisms. The Cell Theory states that all living things are made of one or more cells, or the secretions of those cells, such as the organisms shown in Figure below . For example, shell and bone are built by cells from substances that they secrete into their surroundings. Cells come from cells that already exist, that is, they do not suddenly appear from nowhere. In organisms that are made of many cells (called multicellular organisms), every cell in the organism's body derives from the single cell that results from a fertilized egg. You will learn more about cells and the Cell Theory in Cells: The Cell Theory (Advanced) concept. |
SciQ | SciQ-6691 | blood-circulation, kidney
Title: Why does glomerulus don't allow white blood cells to leave? The glomerulus in nephrons are just a ball of capillaries, so why can't it allow the white blood cells to squeeze though the epithelial cells into Bowman's capsule just like the formation of tissue fluid in other capillaries by filtration? Red blood cells, White blood cells, platelets and proteins with large molecular weight cannot pass through the podocyte and fenestrations in glomerular capillary, but small molecules like water, salts and sugars are filtered out as part of urine.
As these cells and proteins are large to cross through this filter, they remain in the capillary and create osmotic pressure within the capillary. Bowman’s space has osmotic pressure approximately zero. So, only hydrostatic pressure works in this state and help in movement of fluid across the capillary wall.
Via: https://opentextbc.ca/anatomyandphysiology/chapter/25-5-physiology-of-urine-formation/
The following is multiple choice question (with options) to answer.
Which organ in the human body filters blood and excretes urine? | [
"the liver",
"the kidney",
"the bladder",
"the thyroid"
] | B | The kidneys filter all the blood in the body many times each day and produce a total of about 1.5 liters of urine . The kidneys control the amount of water, ions, and other substances in the blood by excreting more or less of them in urine. The kidneys also secrete hormones that help maintain homeostasis. Erythropoietin , for example, is a kidney hormone that stimulates bone marrow to produce red blood cells when more are needed. They also secrete renin, which regulates blood pressure, and calcitriol, the active form of vitamin D, which helps maintain calcium for bones. The kidneys themselves are also regulated by hormones. For example, antidiuretic hormone from the hypothalamus stimulates the kidneys to produce more concentrated urine when the body is low on water. |
SciQ | SciQ-6692 | 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.
Sugars are simple types of what biochemical compounds and possess relatively small molecules? | [
"carbohydrates",
"vegetables",
"proteins",
"lipids"
] | A | Carbohydrates are biochemical compounds that include sugar, starch, glycogen, and cellulose. Sugars are simple carbohydrates with relatively small molecules. Glucose is one of the smallest sugar molecules. Its chemical formula is C 6 H 12 O 6 . This means that a molecule of glucose contains 6 atoms of carbon, 12 atoms of hydrogen, and 6 atoms of oxygen. Plants and some other organisms make glucose in the process of photosynthesis. Living things that cannot make glucose can obtain it by consuming plants or organisms that consume plants. |
SciQ | SciQ-6693 | tissue
Title: Tissues in plants and animals
What is the equivalent connective tissue in plants?
Connective tissue in animals are mostly made up of collagen.
What about in plants?
Connective tissue in animals are mostly made up of collagen
Tissue is not like a simple chemical mixture ; rather tissue means a group or assemblage of cells, obeying certain defining-characteristics.
Animal connective tissues contain collagen mostly in the extracellular matrix. There are also other cell-constituents like phospholipid(membranes), DNA, RNA, etc. Blood is a liquid connective tissue which do not contain collagen in its matrix (plasma)
What is the equivalent connective tissue in plants?
Connective tissue is defined as all the tissues originated from the mesoderm layer of the animal embryo.
Now plants have a different mode of development than animals (plausibly due to evolution in separate route). So no part of a plant-body is homologous with a part of animal-body. It is impossible to bring a compare.
However; plants too; have their extracellular matrix; which is more popular as plant's cell wall (that contain cellulose, hemicellulose, etc.) as well there are intercellular spaces.
Still, if you forcefully want to bring a comparison; then the ground-tissue system of plant maybe called as a rough analogy with connective tissues in animals ( Similarly epidermal tissue of plant maybe a rough analogy with epithelial tissue of animals)
The following is multiple choice question (with options) to answer.
What type of tissue is blood? | [
"nervous",
"connective",
"epithelial",
"muscular"
] | B | Blood Blood is considered a connective tissue because it has a matrix, as shown in Figure 33.17. The living cell types are red blood cells (RBC), also called erythrocytes, and white blood cells (WBC), also called leukocytes. The fluid portion of whole blood, its matrix, is commonly called plasma. |
SciQ | SciQ-6694 | newtonian-mechanics, forces, momentum, collision
Title: Object falls and hits ground - which forces are involved to change its momentum? When an object falls and hits the ground - which forces are involved to change its momentum?
Should $m\vec{g}$ be taken into account of the forces that were involved in the change of momentum?
When an object falls and hits the ground - which forces are involved to change its momentum?
Vectorial sum of all the forces acting on the object will cause the change in momentum of the object.
When the object was in free-fall, its momentum was already changing due to gravity(assuming negligible amount of air resistance) and then it hit the ground.
(Please note that if an object is at rest on the surface of earth doesn't mean there is no gravitational force on the object; it just means that net force on the object is zero).
So from Newton's law:
$$\text{Change in momentum} = \frac{\text{net force}}{\text{mass}}$$.
So in summary you must include all the forces acting on the object when calculating the change in momentum or acceleration .
The following is multiple choice question (with options) to answer.
What is the force that causes objects to fall down to the ground? | [
"pull",
"gravity",
"motion",
"velocity"
] | B | Regardless of what gravity is — a force between masses or the result of curves in space and time — the effects of gravity on motion are well known. You already know that gravity causes objects to fall down to the ground. Gravity affects the motion of objects in other ways as well. |
SciQ | SciQ-6695 | astrophotography
if it is 13 billion light years away wouldn't it take 26 billion light years to take those pictures?
as if light years are a measure of time. A light year is a measure of distance, the distance light travels in a year in a vacuum.
The following is multiple choice question (with options) to answer.
The distance of stars is measured in what terms, meaning the light takes many thousands of years to reach us? | [
"light months",
"light hours",
"light decades",
"light years"
] | D | Viewing distant stars is looking back in time. The stars we see are many thousands of light years away, which means the light takes many thousands of years to reach us. Thus the stars we see in the sky are how they looked thousands of years ago. |
SciQ | SciQ-6696 | 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.
What type of matter often sinks into cracks between rocks? | [
"energy",
"liquid",
"vapor",
"algae"
] | B | |
SciQ | SciQ-6697 | 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.
Name a one-celled organism that can be found on your skin, in the ground, or in all different types of water. | [
"fungus",
"pathogens",
"bacteria",
"virus"
] | C | Cells are found in all different types of environments, and these environments are constantly changing. For example, one-celled organisms, like bacteria, can be found on your skin, in the ground, or in all different types of water. Therefore, cells need a way to protect themselves. This job is done by the cell membrane, which is also known as the plasma membrane. |
SciQ | SciQ-6698 | power, battery, circuit
Regarding your bonus points, the other devices you've listed aren't power storage devices. They can run indefinitely, provided they're powered. A solar cell doesn't hold a charge, so it can't run anything for any amount of time if there's no sun. If there is sun, it can supply its rated power as long as the sun is out. Note again though rated power - you can't run a 5W robot on a 1W solar cell. Same applies for all other power supplies. The are power supplies, not power reserves like a battery.
The following is multiple choice question (with options) to answer.
What type of power is generated using a nonrenewable resource? | [
"nuclear power",
"wind power",
"water power",
"solar power"
] | A | Chuck Szmurlo (Wikimedia: Cszmurlo). Nuclear power is generated using a nonrenewable resource . CC BY 2.5. |
SciQ | SciQ-6699 | earth, geophysics
Title: What is the most optimal earth's axial tilt in terms of variation of seasons? What is the most optimal earth's axial tilt in terms of variation of seasons?
What would be optimal axial tilt for earth that life would exist and change of seasons would be at minimal level? If Earth had 0 inclination to the ecliptic, then life could still exist and there would be no change in seasons. In fact, at latitudes greater than $-23.5^\circ$ and less than $23.5^\circ$, the seasons are already irregular compared with the rest of the planet; they have two points where the Sun shines directly on top of them, effectively making them have two summers. At the equator, there is practically no/minimal variation in seasons already.
The following is multiple choice question (with options) to answer.
The earth is tilted on its what? | [
"compass",
"radius",
"top",
"axis"
] | D | The Earth is tilted on its axis ( Figure above ). This means that as the Earth rotates, one hemisphere has longer days with shorter nights. At the same time the other hemisphere has shorter days and longer nights. For example, in the Northern hemisphere summer begins on June 21. On this date, the North Pole is pointed directly toward the Sun. This is the longest day and shortest night of the year in the Northern Hemisphere. The South Pole is pointed away from the Sun. This means that the Southern Hemisphere experiences its longest night and shortest day ( Figure below ). |
SciQ | SciQ-6700 | research, hri, uncanny-valley
In my personal opinion, there's no doubt something like the Uncanny Valley exists, even though it may not quite take the shape Mori gave it (Bartneck et al., 2007). Artists of all ilk have long been aware of it and have deliberately used it (e.g. Chucky or any zombie movie ever) or suffered when falling into it (the Polar Express being the most notable example). Several explanations have been put forward to explain it (Brenton et al., 2005; MacDorman, 2005; Saygin et al., 2010) and it's been observed in monkeys as well (Steckenfinger and Ghazanfar, 2009), so it's very likely evolutionary in nature.
If you are interested in this area, I'd probably look at how people suffering from autism process faces in general. In this area, there have been a number of studies using real faces (e.g. Scholar search autism "facial features"), as well as artificial faces (e.g. Scholar search autism cartoon faces). This difference in decoding facial expressions might explain why they seem to not feel the effects of the uncanny valley the same way other people do.
As for Kaspar in particular, Blow et al. (2006) goes into some detail on the design decisions involved in Kaspar's face. Also, in a YouTube video, Kaspar's creators cite predictability and simplicity as some of the reasons for his particular design.
References:
The following is multiple choice question (with options) to answer.
What can human facial expressions communicate? | [
"ideas",
"behaviors",
"theories",
"emotions"
] | D | Human facial expressions can communicate a range of emotions. |
SciQ | SciQ-6701 | botany, classification
Title: Is ivy (genus Hedera) a shrub or an herb? It seems like the difference between a bush (shurb) and an herb is that a bush has a woody stem.
What does that make ivy (genus Hedera)? I know that ivy can get a pretty hard stem, does that count as woody? Is there something between a bush and an herb? Woody plants are usually either trees, shrubs, or lianas. Ivies are lianas, they can have 40 years of woody growth rings and bark. The categories are flexible. It's an arbitrary division for convenience, it isn't that clear cut. Bamboos for example, are a woody grass.
https://weedwise.conservationdistrict.org/weeds/english-ivy#foobox-1/7/Untitled-4-copy.jpg
Does that count as a woody plant? yes it's a woody liana.
The following is multiple choice question (with options) to answer.
What are the two types of vascular plants? | [
"dahlias and seed",
"seedless and seed",
"Water and spore",
"ants and seed"
] | B | Vascular plants are further divided into seedless and seed plants. |
SciQ | SciQ-6702 | human-anatomy
In the wrist, you can have palmar flexion, dorsiflexion (extension), ulnar flexion (abduction) and radial flexion (adduction) (Teachmeanatomy).
In the ankle, you can have plantar flexion, dorsiflexion (extension), inversion (inward rotation, adduction) and eversion (outward rotation, abduction). (ScienceDirect).
In the shoulder and hip, raising a limb to the same side as the limb is, is abduction (lateral extension) and raising it to the opposite side is adduction.
Moving the thumb toward the palm (in the same plane as palm) is flexion (adduction) and moving it away from it is extension (abduction).
You can read about flexion and extension and other movements here: Types of Body Movements (BCcampus)
The following is multiple choice question (with options) to answer.
What type of flexion is the bending of the neck or body toward the right or left side? | [
"cylindrical",
"orbital",
"ventral",
"lateral"
] | D | Flexion and Extension Flexion and extension are movements that take place within the sagittal plane and involve anterior or posterior movements of the body or limbs. For the vertebral column, flexion (anterior flexion) is an anterior (forward) bending of the neck or body, while extension involves a posterior-directed motion, such as straightening from a flexed position or bending backward. Lateral flexion is the bending of the neck or body toward the right or left side. These movements of the vertebral column involve both the symphysis joint formed by each intervertebral disc, as well as the plane type of synovial joint formed between the inferior articular processes of one vertebra and the superior articular processes of the next lower vertebra. In the limbs, flexion decreases the angle between the bones (bending of the joint), while extension increases the angle and straightens the joint. For the upper limb, all anterior-going motions are flexion and all posterior-going motions are extension. |
SciQ | SciQ-6703 | human-biology, human-anatomy, terminology, anatomy, etymology
Title: Why is the opposite of plantar flexion called "dorsiflexion"? Why is the action of flexing the foot so that the toes move anteriorly/superiorly (i.e. in the direction opposite that which they move during plantar flexion) described as "dorsiflexion?" In the same vein, why is the top surface of the foot called the "dorsal surface?"
If anything, the action opposite to plantar flexion moves the foot in the ventral direction, doesn't it? And surely if you've ever seen a human in the anatomical position, you can see that there's nothing dorsal about the top surface of the foot - it's superior, perhaps, but by no means dorsal. Anatomical terms must be able to fit a wide variety of organisms, from insects to fish, dogs, horses, chimpanzees to humans. That's why the terms are sometimes confusing to people who are thinking only of bipedal humans.
In anatomy, the dorsum is the upper side of animals that typically run fly, swim or crawl in a horizontal position. In vertebrates the dorsum contains the backbone. In such an animal the "ground side" is the ventrum.
Due to varied orientation on quadrupedal mammals (where the term is more appropriately used) the "back"-side of the hand, the "top"-side of the foot and the upper surface of the tongue are referred to by the term dorsum.
Does this picture help? Note the dorsal surfaces of the body, muzzle, feet.
In anatomy, the sole of the foot is called the plantar surface. The top of the foot is called the dorsum of the foot. (Imagine us walking on all fours like apes.) Therefore when you extend your foot, it's called plantar flexion; when you flex your foot upwards towards your head, it's called dorsiflexion.
Similarly, the arteries feeding the bottom of your foot form the plantar arch. Those feeding the top are the dorsal artery (or the dorsalis pedis).
Because anatomy must describe other animals than ourselves with other orientations, it must be consistent. In a quadruped, the dorsum of the tongue and the feet do actually point to it's "back" surface. See the picture below:
The following is multiple choice question (with options) to answer.
Common wisdom has it that the temporal bone (temporal = “time”) is so named because this area of the head (the temple) is where hair typically first turns gray, indicating the passage of what? | [
"ships",
"birth",
"time",
"wealth"
] | C | Temporal Bone The temporal bone forms the lower lateral side of the skull (see Figure 7.5). Common wisdom has it that the temporal bone (temporal = “time”) is so named because this area of the head (the temple) is where hair typically first turns gray, indicating the passage of time. The temporal bone is subdivided into several regions (Figure 7.7). The flattened, upper portion is the squamous portion of the temporal bone. Below this area and projecting anteriorly is the zygomatic process of the temporal bone, which forms the posterior portion of the zygomatic arch. Posteriorly is the mastoid portion of the temporal bone. Projecting inferiorly from this region is a large prominence, the mastoid process, which serves as a muscle attachment site. The mastoid process can easily be felt on the side of the head just behind your earlobe. On the interior of the skull, the petrous portion of each. |
SciQ | SciQ-6704 | development
Title: How detachment/separation works in biology? It might be a strange question, but I'm interested in the mechanics of separation/detachment during asexual reproduction, for example when an organism reproduces by budding (I don't mean cellular budding like baker's yeast). When the newly formed body is fully matured it detaches itself from the parent / original body.
It might not be caused by a specific tissue, as animals with not so differentiated bodies are (also) capable of such, but I could easily be wrong. Is this (the detachment) triggered by changes in the cell membrane? I can't really think of other explanations. Reproductive budding and what you call 'cellular budding' are really highly related processes. Budding as a form of reproduction essentially partitions protein aggregates and damaged cellular components into the host or mother and builds fresh or 'young' cells on the opposite side of a partition. To begin understanding this look at Saccharomyces cerevisiae (budding yeast) which forms protein rings (from the septin proteins) at the membrane, around the bud neck which separates the mother and daughter cells Hartwell 1971. This ring acts a partition that in part, withholds protein aggregates and certain proteins from diffusing from the mother to the daughter. This protein ring is an example of how cells limit diffusion of proteins and cellular components to the daughter cell. Another good example that comes to mind is Linder 2007, though it is done in E Coli, not budding yeast, where mother cells maintain protein aggregates and age, while the daughter cells are given fresh components and are therefore more fresh and 'young'.
Now like you mention, imagine this process in a multicellular organism to be fundamentally the same. At some point the multicellular organism will start an outgrowth of cells, while restricting what materials are given to the daughter cells to maintain their youth. And eventually a new organism will have been created. Some of the details will be different, but the fundamental process is is quite similar. In that you start with an old cell that creates a new cell from scratch, but rather than splitting all cellular components equally between mother and daughter, the daughter cells is made in peak condition while the mother cell retains much of the cell 'junk' like protein aggregates.
Hopefully that starts to answer your question.
The following is multiple choice question (with options) to answer.
Catenulids typically reproduce asexually by budding where? | [
"their neuronal end",
"their posterior end",
"their anterior end",
"their analogous end"
] | B | |
SciQ | SciQ-6705 | homework, reproduction, embryology
Title: Which process is needed to complete male reproductive development? In order to properly complete male reproductive development:
A. primordial germ cells must begin Meiosis I in utero.
B. Sertoli cells must produce testosterone.
C. Dihydrotestosterone must masculinize Wolffian duct derivatives
D. the paramesonephric ducts must degenerate
E. the metanephros must form the genital epithelium
My attempt: I think the answer is C because testosterone turns into DHT which then masculinzing the wolffian duct. Other people I am studying with claim the answer is D (which is true) except that I dont think the loss of the paramesonephric duct is needed to complete male repro development. Regarding option C:
Although it is correct that testosterone is converted into DHT, it is the former, not the latter, which is responsible for differentiation of the mesonephric (a.k.a. Wolffian) ducts:
Between 8 and 12 weeks, the initial secretion of testosterone stimulates mesonephric ducts to transform into a system of organs—the epididymis, vas deferens, and seminal vesicle—that connect the testes with the urethra.*
DHT (dihydrotestosterone) is produced in the Leydig cells by the 5α-Reductase enzyme. It is required for induction of the external male genitalia (urethra, penis, and scrotum) and prostate from the embryonic ureteral groove, and for testicular descent into scrotum.
Regarding option D:
Sertoli cells secrete Anti Müllerian Hormone (AMH), which causes degeneration of the müllerian (a.k.a. paramesonephric) ducts between weeks 8 and 10. It is normal to speak about degeneration of the müllerian ducts as a defining aspect of male embryology, and thus I believe answer D is correct. Your point is taken, however:
Nevertheless, small müllerian duct remnants can be detected in the adult male, including a small cap of tissue associated with the testis, called the appendix testis, and an expansion of the prostatic urethra, called the prostatic utricle.*
The following is multiple choice question (with options) to answer.
What gland secretes a fluid that mixes with sperm to help form semen? | [
"thy·mus",
"thyroid",
"testicle",
"prostate gland"
] | D | The prostate gland secretes a fluid that mixes with sperm to help form semen. Semen is a whitish liquid that contains sperm. It passes through the urethra and out of the body. |
SciQ | SciQ-6706 | earthquakes
Title: What is that spooky humming sound heard in earthquake footages? In most of the earthquake footages filmed outside during the earthquake that hit Mexico City on September 9, 2017 there was a distinctive streak of hum in rapid succession that could be heard in the background. It sounded like someone is constantly hitting the tuning forks onto a light tower like 2 times per second.
You can find numerous footages on youtube, but I picked one and fetched the audio portion covering the hums, you can listen to the audio at this link here (sorry I did not know how to upload an audio to SE).
Here is the waveform of the sound
What is that sound? What is causing this sound? If this was buildings or surrounding objects, why is there a pattern? Why is this sound heard in every footage no matter where they are filmed as long as they were filmed outside. Wailing sirens.
Examples 1, 2 where you see people come running out, i.e. exactly when you'd expect sirens, or 3, or 4 and 5 where they are explicitly mentioned.
The following is multiple choice question (with options) to answer.
During an earthquake what causes seismic waves? | [
"low tide",
"rock displacement",
"high winds",
"Currents"
] | B | In an earthquake, seismic waves are generated by rock displacement. |
SciQ | SciQ-6707 | electromagnetic-radiation, visible-light, aether
Title: If sound travels through matter what medium does light travel through? So sound is a wave and is basically just vibrations, an atom vibrates causing another next to it vibrate and so on until it finally reaches our ears to become sound.
If that's normally how waves behaves, what about light? I understand it's also a particle but something must have caused its starting point to influence its next point in space thereby allowing it to travel through space. what is the cause and effect relationship that allows light to propagate through space? I ruled out matter because most visible light is blocked by matter. The process of light propagation is described by the Maxwell equations.
$$ \nabla\cdot{\bf D} = \rho $$
$$ \nabla\cdot{\bf B} = 0 $$
$$ \nabla\times{\bf E} = - {{\partial{\bf B}}\over{\partial t}} $$
$$ \nabla\times{\bf H} = {\bf J} + {{\partial{\bf D}}\over{\partial t}} $$
These equations say (in simple terms) that: change in the electric field is causing a change in magnetic field, while change in magnetic field is causing a change in the electric field.
The original source of electromagnetic waves is some oscillating charge (for instance an electron) which has an electric field around it. This field is changing (because the charge is oscillating). Therefore (according to the fourth equation) a magnetic field $H$ is formed. But the creation of magnetic field is in fact a change in magnetic field. This leads (according to the third equation) to creation of new electric field $E$. But this change in $E$ leads to $H$, which leads to $E$, etc.
The following is multiple choice question (with options) to answer.
What term describes waves that travel through matter? | [
"heat waves",
"mechanical waves",
"water waves",
"replaced waves"
] | B | Waves that travel through matter—such as the fabric of a flag—are called mechanical waves. The matter they travel through is called the medium. When the energy of a wave passes through the medium, particles of the medium move. The more energy the wave has, the farther the particles of the medium move. The distance the particles move is measured by the wave’s amplitude. |
SciQ | SciQ-6708 | metal, toxicity, radioactivity
239Pu's radioactivity is in the form of alpha particles, which are only dangerous if emitted internally, because they can't penetrate the epidermis. The hazard then seems to me like it would depend crucially on how the internal exposure occurred. If you eat an alpha emitter, then it will stay in your body until it's either excreted or decays. The half-life for excretion of organic or metallic Hg is on the order of months, so that's probably a reasonable order-of-magnitude estimate for other heavy metals. On the other hand, there are people at nuclear weapons labs who do machining of plutonium pieces, and this kicks up plutonium dust. They do this machining inside glove boxes, and I assume the chips and dust are swept up very carefully. The dust can be breathed in, and microgram particles that get into your lungs are likely to remain there for the rest of your life (Lenntech, ATSDR 2010). From the lungs, it can also migrate to the bones or liver. ("Much less than 1%" of ingested Pu would do so.)
The following is multiple choice question (with options) to answer.
What type of radioactive decay is generally only dangerous when emitted inside the body? | [
"variant decay",
"nucleus decay",
"alpha decay",
"ionic decay"
] | C | All types of radioactive decay pose risks to living things, but alpha decay is the least dangerous. That’s because alpha particles are relatively heavy, so they can travel only a few centimeters through the air. They also are not very penetrating. For example, they can’t pass through a sheet of paper or thin layer of clothing. They may burn the skin, but they can’t penetrate to the tissues underneath the skin. However, if alpha particles are emitted inside the body, they can do more damage. One way this can happen is by inhaling cigarette smoke. People who smoke actually inhale the radioactive element polonium-210. It undergoes alpha decay in the lungs. Over time, exposure to alpha particles may cause lung cancer. |
SciQ | SciQ-6709 | energy, definition
Centuries ago, before people appreciated the fundamental role of maths in physics, they believed e.g. that the heat - a form of energy - was a material called the phlogiston. But, a long long time ago experiments were done to prove that such a picture was invalid. Einstein's $E=mc^2$ partly revived the idea - energy is equivalent to mass - but even the mass in this formula has to be viewed as a number rather than something that is made out of pieces that can be "touched".
Energy has many forms - terms contributing to the total energy - that are more "concrete" than the concept of energy itself. But the very strength of the concept of energy is that it is universal and not concrete: one may convert energy from one form to another. This multiplicity of forms doesn't make the concept of energy ill-defined in any sense.
Because of energy's relationship with time above, the abstract definition of energy - the Hamiltonian - is a concept that knows all about the evolution of the physical system in time (any physical system). This fact is particularly obvious in the case of quantum mechanics where the Hamiltonian enters the Schrödinger or Heisenberg equations of motion, being put equal to a time-derivative of the state (or operators).
The total energy is conserved but it is useful because despite the conservation of the total number, the energy can have many forms, depending on the context. Energy is useful and allows us to say something about the final state from the initial state even without solving the exact problem how the system looks at any moment in between.
Work is just a process in which energy is transformed from one form (e.g. energy stored in sugars and fats in muscles) to another form (furniture's potential energy when it's being brought to the 8th floor on the staircase). That's when "work" is meant as a qualitative concept. When it's a quantitative concept, it's the amount of energy that was transformed from one form to another; in practical applications, we usually mean that it was transformed from muscles or the electrical grid or a battery or another "storage" to a form of energy that is "useful" - but of course, these labels of being "useful" are not a part of physics, they are a part of the engineering or applications (our subjective appraisals).
The following is multiple choice question (with options) to answer.
Energy that is stored in a person or object is called? | [
"vertical energy",
"kinetic energy",
"potential energy",
"mechanical energy"
] | C | Potential energy is energy that is stored in a person or object. |
SciQ | SciQ-6710 | materials
Title: Is there a lighter-than-air foam material? Soap bubble foam made with helium floats up, but due to extreme fragility hardly counts as "material". There are many solid foam materials though - PUR foam, or styrofoam to name the most common. They typically use carbon dioxide for inflation though (usually produced from precursors of the foam, as a desirable side effect of their reaction).
But it shouldn't be too difficult to make solid foam filled with helium (or hydrogen) in proportions assuring positive buoyancy in air, and I can imagine desirability of it, at least as a filler in applications where mass costs a premium (transport, aviation) even if its structural properties were to be too poor for any other purpose.
Is such material produced? Is it used anywhere? Or if not, why? No matter how good you seal it, when you inflate a balloon with Helium it will stay up for a while, but after a few days, it will lose its pressure.
Enough to realise that in solids, there is also a phenomenon of mass diffusivity, and therefore your foam will not retain the gas. This phenomenon is also called Permeation
Diffusivity in solids is very complex, and 'mostly' cannot be described with an equation as simple as with Fick's laws, and, in many cases, is not even isotropic. But there is still a condition that needs to be met to diffuse: the particle/atom you consider can place itself within the crystallography/pattern of your material. unfortunately for Helium, it is too small and will diffuse through all reasonable materials.
Diffusivity in solids is unfortunately making us unable to isolate a gaz but it
is also positively used in a lot of fields.
The most investigated is probably in microelectronics to make local implants of ions in semiconductors and therefore change locally its electrical properties.
The following is multiple choice question (with options) to answer.
What is a sac filled with fluid or other material? | [
"a lesion",
"a cyst",
"a receptacle",
"Golgi apparatus"
] | B | Cysts may develop in the ovaries. A cyst is a sac filled with fluid or other material. Ovarian cysts are usually harmless and often disappear on their own. However, some cysts may be painful and require surgery. |
SciQ | SciQ-6711 | thermodynamics
Title: Enthalpy change for exothermic and endothermic reactions I understood the concept behind endothermic and exothermic but finding it hard to understand it numerically.Let me describe my confusion through example.
Suppose for a reaction,
reactants require energy=$\rm40~J$
which on forming product give energy=$\rm50~J$ (so yes it is exomthermic)
where change in enthaply=$\rm10~J$
But as per the equation:
"Enthalpy change=Enthalpy of products- Enthalpy of reactants."
since enthalpy at constant pressure is Total heat content.
So I should have
Change in enthalpy=[U(internal energy)-50]-[U+40]=-90J
Could You explain it where I am getting this wrong? Is my understanding of enthalpy correct? According to the definition,
Enthalpy = Enthalpy(products) - Enthalpy(reactants), this should be followed.
When you are saying that 40 J are used up it means that 40 J are used in transforming the reactants to an activated complex(reaction intermediate) and when you say that 50J are released then it means that 50J is liberated when this activated complex is transformed to the product.
Assume that the energy of the activated complex be 0, then the energy of the reactant must be -40J(because 40J are required to convert reactant to the activated complex) , and the energy of the products should be -50J( because energy is released in converting the complex to the product)
Enthalpy(products)=-50J
Enthalpy(reactants)=-40J
Therefore,
Enthalpy = (-50)-(-40) J = -10J.
The following is multiple choice question (with options) to answer.
What is released during an enthalpy reaction? | [
"sound",
"gold",
"precipitation",
"heat"
] | D | The enthalpy of the reactants is greater than the enthalpy of the products. During the course of the reaction, heat is released to the surroundings. |
SciQ | SciQ-6712 | ionic-compounds, conductivity
Title: Why are ionic compounds bad conductors of electricity in solid state? I understand the fact that ionic compounds are good conductors of electricity in molten state. But why aren't they good conductors in solid state. Cannot ions vibrate about their mean position and transfer electricity in the same way as they transfer heat? Electric charge is transferred by physically moving charged particles around. In the case of an electric current moving through a wire (for example), the electrons are moving.
In an ionic compound, the ions are locked in place. They can move around a little bit, but there is not much translational motion - the ions stay in their places on the crystal lattice. In addition, the ions are "happy" with the number of electrons that they have. The ions formed in the first place by giving up or accepting electrons in order to minimize the overall potential energy of the system. If an anion were to transfer an electron back to a cation (for example) the energy of the system would increase, and so in general, transfer of electrons after the compound has formed is not favorable.
In solution or in a molten state, the ions themselves can move around - they become the charge carriers. In a solid, the ions can't move, and so electricity cannot be easily transferred.
You mentioned heat transfer - heat is the transfer of the kinetic energy of atoms and molecules. Heat can still be transferred (in some cases quite easily) in an ionic solid because, as you said, ions can vibrate about a mean position. When this happens they bump into their neighbors, which spreads the kinetic energy around.
In summary, ionic compounds don't conduct electricity very well because the charge carriers can't move through the crystal. They can conduct heat because the kinetic energy itself is the "heat carrier" - it can be transferred without moving ions too far from their mean positions.
The following is multiple choice question (with options) to answer.
Solutions of ionic compounds and melted ionic compounds conduct what? | [
"sound waves",
"electricity",
"light",
"radiation"
] | B | Solutions of ionic compounds and melted ionic compounds conduct electricity, but solid materials do not. |
SciQ | SciQ-6713 | quantum-mechanics, newtonian-mechanics, string-theory, quantum-interpretations, atoms
Title: Quantum mechanics threshold First of all I beg your forgiveness as I am not a physicist and the question I am going to ask may sound silly.
I am aware that beyond a certain threshold in the hierarchy of building blocks of matter (electrons, atoms, etc.) the 'standard' laws of physics (e.g. Newtonian physics) do not apply and we enter a totally different environment where the so called quantum mechanics apply.
The following is multiple choice question (with options) to answer.
Quantum mechanics involves the study of material at what level? | [
"atomic",
"cellular",
"chemical",
"physical"
] | A | Quantum mechanics involves the study of material at the atomic level. |
SciQ | SciQ-6714 | ## Ch112
The aorta carries blood away from the heart at a speed of about 39 cm/s and has a radius of approximately 1.0 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.072 cm/s, and the radius is about 6.2 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
• solve in the same approach...
The aorta carries blood away from the heart at a speed of about 44 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.071 cm/s, and the radius is about 6.4 x 10-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Solution:
The volume has to be the same, so:
44cm/s * 1.44pi cm^2 = 199.05 cm^3/s
so x(.071cm/s * pi*.00064^2) = 199.05cm^3/s
x = (44 * 1.44pi)/(.071 * pi * .00064^2) = 2.17869718 * 10^9 capillaries
• The aorta carries blood away from the heart at a speed of about 37 cm/s and has a radius of approximately 1.2 cm. The aorta branches eventually into a large number of tiny capillaries that distribute the blood to the various body organs. In a capillary, the blood speed is approximately 0.069 cm/s, and the radius is about 6.3 x 10^-4 cm. Treat the blood as an incompressible fluid, and use these data to determine the approximate number of capillaries in the human body.
Flow rate = Cross sectional area * speed
Blood flow from the aorta = (pi)(1.2)^2(37) = 167.38 cm^3/sec.
The following is multiple choice question (with options) to answer.
What is the name of muscular blood vessels that carry blood away from the heart? | [
"Veins",
"Aorta",
"tubes",
"arteries"
] | D | Arteries are muscular blood vessels that carry blood away from the heart. They have thick walls that can withstand the pressure of blood pumped by the heart. Arteries generally carry oxygen-rich blood. The largest artery is the aorta, which receives blood directly from the heart. It branches to form smaller and smaller arteries throughout the body. The smallest arteries are called arterioles. |
SciQ | SciQ-6715 | mass-spectrometry
Title: What is the highest relative abundance for diatomic bromine? I was introduced to this thing today, and saw a graph showing the detection of ions with different relative abundances.
Just as an example here, $\ce{Br2}$ is shown a detection chart. And at $160~\mathrm{m/z}$ the ion has the highest relative abundance, but why? Since the $\mathrm{m/z}$ ratio is just the mass, for $\mathrm{z}$ is always $+1$, the one which is supposed to have the highest peak should be at $162$? In $\ce{Br2}$, the possible combinations of isotopes are:
$\ce{^{79}Br-^{79}Br} : \mathrm{m/z}~158$
$\ce{^{79}Br-^{81}Br} : \mathrm{m/z}~160$
$\ce{^{81}Br-^{79}Br} : \mathrm{m/z}~160$
$\ce{^{81}Br-^{81}Br} : \mathrm{m/z}~162$
The following is multiple choice question (with options) to answer.
He mass spectrometer measures the percent abundance of different what? | [
"reactions",
"organisms",
"isotopes",
"Proteins"
] | C | The mass spectrometer measures the percent abundance of different isotopes in a given sample. |
SciQ | SciQ-6716 | ethology, mammals, language
Title: Can dolphins actually communicate linguistically? Humans use "language." By language, I mean the thing I am using right now to talk to you.
I know dolphins and orcas have very complex communication systems and also seem to process linguistic and gestural commands.
But do they have their own languages? Where is the evidence for or against? If we take two group of dolphins Group A and Group B, would Group A speak one language and Group B speak another? Dolphins and orcas do have dialects. Of course there are species specific dialects and it has been shown that orcas reared with bottlenose dolphins tend to learn the latter's dialect. Dolphins of the same species also seem to have regional dialects, as mentioned in this BBC post (I personally do not trust in non-research articles much, but nonetheless in this case the article indicates a certain possibility of a phenomenon). However, this page also reports the same finding and this source seems to be much more reliable. There are citations too that are at present inaccessible to me. Both the sources say that bottlenose dolphins from Shannon estuary in Ireland, "speak" different dialect compared to those from Cardigan Bay in Wales.
The actual research work is this:
Hickey, R. (2005) Comparison of whistle repertoire and characteristics between Cardigan Bay and the Shannon estuary
populations of Bottlenose dolphins (Tursiops truncatus) with
implications for passive and active survey techniques. School of
Biological Sciences, University of Wales, Bangor
Apart from having regional dialects, the cetacean communication also seems to have other features of a "language". I am pasting excerpts from this article which basically reports a study on the acoustic communication or codas in sperm whales. This may apply to dolphins as well.
Individuals within social units have preferred associates among
members (Gero et al. 2008), indicating differences in the way an
individual interacts with other members of its unit. These preferred
associations among unit members suggest the possibility of an
individual discrimination system.
The following is multiple choice question (with options) to answer.
For what kind of animal is communication essential? | [
"anti-social animals",
"migrating animals",
"social animals",
"new born animals"
] | C | Communication is any way that animals share information. Many animals live in social groups. For these animals, being able to communicate is essential. Communicating increases the ability of group members to cooperate and avoid conflict. Communication may help animals work together to find food and defend themselves from predators. It also helps them find mates and care for their offspring. In addition, communication helps adult animals teach the next generation learned behaviors. Therefore, communication generally improves the chances of animals surviving and reproducing. |
SciQ | SciQ-6717 | waves, interference, wavelength, superposition
The wavelength is the distance of a "cycle". Take the horizontal length between any two crests, or any two troughs, and what you get is called the wavelength. In physics, this is notated with the $\lambda$ symbol (the Greek letter Lambda). In the plot above, the wavelength has a value of $\pi$.
The amplitude is the height from the centre line to either the crest or the trough.
Destructive interference happens when the squared amplitude of the sum of the waves is lower than the sum of the squared amplitudes of the waves.
Therefore, the interference between two waves is the "most destructive" when the phase difference is an odd number of half-wavelengths, as shown in the plot above with the "$\pi/2$", "$3\pi/2$", "$5\pi/2$" points on the horizontal axis.
The following is multiple choice question (with options) to answer.
The wavelength of a wave is the distance between corresponding points on what? | [
"adjacent waves",
"spectrum",
"distant waves",
"basic waves"
] | A | Q: The wavelength of a wave is the distance between corresponding points on adjacent waves. For example, it is the distance between two adjacent crests in the transverse waves in the diagram. Infer how wave frequency is related to wavelength. |
SciQ | SciQ-6718 | ocean, waves
Title: What causes waves to form the characteristic "breaking" shape as they approach the shoreline? We all know that as waves approach the shallow shores, the waves begin to form a characteristic shape. The upper portion of these breaking waves appears to curl forward and downwards over the bottom segment of the wave, before breaking into "white wash". The image below illustrates what this characteristic shape looks like:
The following is multiple choice question (with options) to answer.
Sandblasting a surface exemplifies what form of erosion? | [
"water",
"wind",
"glacial",
"abrasion"
] | D | Did you ever see workers sandblasting a building to clean it? Sand is blown onto the surface to scour away dirt and debris. Wind-blown sand has the same effect. It scours and polishes rocks and other surfaces. Wind-blown sand may carve rocks into interesting shapes ( Figure below ). This form of erosion is called abrasion. It occurs any time rough sediments are blown or dragged over surfaces. Can you think of other ways abrasion might occur?. |
SciQ | SciQ-6719 | mycology
Title: How do fairy rings propagate? It was somewhat new to me that mushrooms usually aren't individual organisms, but are merely the visible bodies of a bunch of fungi living in the soil. I know that mushrooms emit spores to reproduce, but what has been bizarre to me is how fairy rings form. Why do the fruiting bodies arrange themselves in a more or less circular shape, as opposed to the random scattering one would expect from wind-borne spores? When a fungal spore germinates in a suitable location, the growing mycelium will spread underground in all directions. In the ideal situation, the result is that the mycelium will become circular. Over time, the center of the mycelium will die out whereas the newly formed mycelium (underground) will develop the familiar mushrooms above ground and this will result in a fairy ring.
The following is multiple choice question (with options) to answer.
How do fungus-like protists such as slime molds reproduce? | [
"asexually",
"sexually",
"with spores",
"photosynthesis"
] | C | Fungus-like protists are molds. They are absorptive feeders, found on decaying organic matter. They resemble fungi and reproduce with spores as fungi do. Examples of fungus-like protists include slime molds and water molds. |
SciQ | SciQ-6720 | 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.
Exchange occurs directly with the external environment in what type of organisms? | [
"multicellular organisms",
"cell clusters",
"unicellular organisms",
"hematopoietic organisms"
] | C | |
SciQ | SciQ-6721 | biochemistry, neuroscience, brain, neuroanatomy
Title: The human brain in numbers I: neurons Even though knowing the number of neurons in a functional unit or with the same function is not of main importance, it may be interesting to know their orders of magnitude, especially in the human brain. For example:
|------------------|------------------|
| cerebellum | 100,000,000,000 |
| cortex | 20,000,000,000 |
| telencephalon | 10,000,000,000 |
| brainstem | 1,000,000,000 |
| sensory neurons | |
| haptic | 500,000,000 |
| visual | 100,000,000 |
| auditory | 2,000 |
| limbic system | |
| amygdala | 10,000,000 |
|------------------|------------------|
The following is multiple choice question (with options) to answer.
Which part of a neuron contains the nucleus and most of the major organelles? | [
"retinal body",
"simple body",
"organ body",
"cell body"
] | D | Parts of a Neuron As you learned in the first section, the main part of a neuron is the cell body, which is also known as the soma (soma = “body”). The cell body contains the nucleus and most of the major organelles. But what makes neurons special is that they have many extensions of their cell membranes, which are generally referred to as processes. Neurons are usually described as having one, and only one, axon—a fiber that emerges from the cell body and projects to target cells. That single axon can branch repeatedly to communicate with many target cells. It is the axon that propagates the nerve impulse, which is communicated to one or more cells. The other processes of the neuron are dendrites, which receive information from other neurons at specialized areas of contact called synapses. The dendrites are usually highly branched processes, providing locations for other neurons to communicate with the cell body. Information flows through a neuron from the dendrites, across the cell body, and down the axon. This gives the neuron a polarity—meaning that information flows in this one direction. Figure 12.8 shows the relationship of these parts to one another. |
SciQ | SciQ-6722 | the-moon, gravity, tidal-forces
Title: How does the Moon's gravity affect Earth's oceans despite Earth's stronger gravitational pull? Given that Earth has a much stronger gravitational pull than the Moon, how does the Moon have any influence on Earth's oceans? Everything in the universe has a gravitational influence on everything else in the universe. It isn't a question of the strongest gravitational pull winning out and all the others doing nothing.
The Earth is the strongest pull on the oceans, but the Moon and the Sun both have easily measurable effect in addition to the Earth's. Other bodies (Venus, Jupiter, a small asteroid in another galaxy,....) all have much smaller effects which will be hard or impossible to detect amidst the noise due to waves and so on.
The following is multiple choice question (with options) to answer.
The oceans affect earth’s atmosphere and influence its what? | [
"earthquakes",
"volcanoes",
"climate",
"mountains"
] | C | Much of Earth’s surface is covered with oceans. That’s why Earth is called the “water planet. ” Without all that water, Earth would be a very different place. The oceans affect Earth’s atmosphere and influence its climate. An incredible diversity of living things inhabit the ocean as well. You might think that oceans have always covered Earth’s surface, but you would be wrong!. |
SciQ | SciQ-6723 | bacteriology
Saier, MH. & Bogdanov, V. (2013) Membranous Organelles in Bacteria. JOURNAL OF MOLECULAR MICROBIOLOGY AND BIOTECHNOLOGY 23: 5-12 DOI: 10.1159/000346496
Free full text here.
The language used in this review seems to support the existence of mesosomes as some sort of intermediate in the formation of intracellular membranes in prokaryotes. This review is a polemic in favour of the idea that prokaryotes do indeed contain intracellular membrane-bounded compartments. It has no abstract, but the first paragraph gives a flavour of its stance:
The traditional view of life on Earth divides the living world into two major groups, prokaryotes and eukaryotes. These two groups were originally suggested to differ in very basic respects. While eukaryotes had complex cell structures including a cytoskeleton and intracellular membrane-bounded organelles, prokaryotes were believed to lack them. In fact, numerous textbooks and current sources still note this distinction and hold it to be true. For example, in Campbell’s Biology [Campbell, 1993, p. 515] it is stated without equivocation: ‘Prokaryotic cells lack membrane-enclosed organelles.’ In ‘Functional Anatomy of Prokaryotic and Eukaryotic Cells’ [Tortora et al., 2009, chapt. 4] it is similarly claimed that ‘Prokaryotes lack membrane-enclosed organelles, specialized structures that carry on various activities’. In the current Wikipedia, under ‘Prokaryote’ the following statement can be found: ‘The prokaryotes are a group of organisms whose cells lack a cell nucleus (karyon) or any other membrane-bounded organelles’. In the same online compendium under ‘Organelle’, one can read: ‘whilst prokaryotes do not possess organelles per se, some do contain protein-based microcompartments’. Proteinceous microcompartments will be the subject of a forthcoming Journal of Molecular Microbiology and Biotechnology written symposium, but this one will show that these generalizations, suggesting a lack of subcellular compartmentalization in prokaryotes, are blatantly in error [Murat et al., 2010a].
The following is multiple choice question (with options) to answer.
What are surrounded by a cell wall consisting of peptidoglycan? | [
"amoeba",
"viruses",
"protozoa",
"bacteria"
] | D | Bacteria are surrounded by a cell wall consisting of peptidoglycan . This complex molecule consists of sugars and amino acids. The cell wall is important for protecting bacteria. The cell wall is so important that some antibiotics, such as penicillin, kill bacteria by preventing the cell wall from forming. |
SciQ | SciQ-6724 | herpetology, poison
Title: Poisonous Snakes consuming poison (chemical) While travelling with my Son to a religious shrine, we saw a dead snake lying on the road.
My Son asked a curious question to me "Dad, if Poisonous snakes consume poison (Chemical), Will they die"?
I feel the answer is depends upon the type of poisonous snake viz Cobra, Python etc and how much the reptile has consumed the poison. i.e. quantity.
What is the correct answer? If any living thing consumes enough of a poison it will die. But I feel that is not what you want to ask.
Perhaps you meant to ask if a snake will die if it drinks its own venom? That would make more sense as a question.
In English, venom and poison mean different things when talking about a toxic chemical produced by an animal.
Poison is a toxic chemical produced by an animal that is meant to be ingested/eat/drink.
Venom is a toxic chemical produced by an animal that is meant to be injected into the bloodstream.
So a snake bite has venom, but a colourful tree frog has poison on its skin.
Venom is typically not nearly as harmful if ingested, even if by a different animal, because it is meant to act directly in the bloodstream
The following is multiple choice question (with options) to answer.
Snake venom may join the class of drugs collectively known as thrombolytic agents, which can help speed up the degradation of an abnormal what? | [
"clot",
"brain",
"bone",
"bleed"
] | A | on a daily basis as a preventive measure. However, aspirin can also lead to serious side effects, including increasing the risk of ulcers. A patient is well advised to consult a physician before beginning any aspirin regimen. A class of drugs collectively known as thrombolytic agents can help speed up the degradation of an abnormal clot. If a thrombolytic agent is administered to a patient within 3 hours following a thrombotic stroke, the patient’s prognosis improves significantly. However, some strokes are not caused by thrombi, but by hemorrhage. Thus, the cause must be determined before treatment begins. Tissue plasminogen activator is an enzyme that catalyzes the conversion of plasminogen to plasmin, the primary enzyme that breaks down clots. It is released naturally by endothelial cells but is also used in clinical medicine. New research is progressing using compounds isolated from the venom of some species of snakes, particularly vipers and cobras, which may eventually have therapeutic value as thrombolytic agents. |
SciQ | SciQ-6725 | neuroscience, neurophysiology, anatomy, neuroanatomy
Title: Is C. elegans always observed with precisely 302 neurons? Are there ever individual viable exceptions? This answer mentions that the C. elegans hermaphrodite has exactly 302 distinct neurons. This has made it a very effective model for a variety of types of biological research, including neurology and cell differentiation. It is also currently the only organism with a completely mapped connectome.
But the word "always" made me wonder - has a viable specimen ever been verified to naturally have a number of neurons other than 302? Not as a result of an experiment, just naturally? According to the highly respected WORMATLAS: A Database of Behavioral and Structural Anatomy of Caenorhabditis elegans, the number is invariable in this animal, one of the most studied in the world.
There are 302 neurons in the nervous system of C. elegans; this number is invariant between animals. Each neuron has a unique combination of properties, such as morphology, connectivity and position, so that every neuron may be given a unique label. Groups of neurons that differ from each other only in position have been assigned to classes. There are 118 classes that have been made using these criteria, the class sizes ranging from 1 to 13. Thus C. elegans has a rich variety of neuron types in spite of having only a small total complement of neurons. (Emphasis mine)
From the above, you might guess that the number of synapses are not, however.
The full list of synapses for hermaphrodite (including larval stages) and adult male are currently being reviewed and revised for the Wormwiring Project. All data comes from re/analysis of the sections for the hermaphrodite N2U, N2T, N2W and JSE animals, and male N2Y and n930 animals. The total counts of both electrical and chemical synapses are likely to be substantially higher than what was reported in the Mind of a Worm.
Would I be surprised if someone found a different number in a particular specimen? No more so than when people are born with four kidneys, a parasitized twin, etc.
Edited to Add:
An article, Mutations that affect neural cell lineages and cell fates during the development of the nematode Caenorhabditis elegans has identified mutations with more or fewer neurons:
The following is multiple choice question (with options) to answer.
Thousands of receptor cells that detect the sex attractant equip each filament of what structure? | [
"flagella",
"molecule",
"optic nerve",
"antenna"
] | D | |
SciQ | SciQ-6726 | solutions
Title: Can the total amount of solution be found as a ratio between molar mass of a component and total mass of solution? I wonder whether the following relation is true:
$$n_\mathrm{solvent} + n_\mathrm{solute} = \frac{M}{m_\mathrm{solvent} + m_\mathrm{solute}},$$
where $M$ is the molar mass of the component, $n$ is the amount of substance and $m$ is the mass.
It was derived assuming $n = m/M,$ $n = n_\mathrm{solvent} + n_\mathrm{solute}$ and $m = m_\mathrm{solvent} + m_\mathrm{solute}.$
I don't think this is true, but I wanted to be sure before doing anything weird on a test. To sum up the comments, only the following relation for the total amount of solution $n_\mathrm{tot}$ is universally true:
$$n_\mathrm{tot} = n_\mathrm{solvent} + n_\mathrm{solute} = \frac{m_\mathrm{solvent}}{M_\mathrm{solvent}} + \frac{m_\mathrm{solute}}{M_\mathrm{solute}}\tag{1}$$
The best you can do is to assume that $n_\mathrm{tot}\approx n_\mathrm{solvent}$ for the diluted solutions of small molecules. Also, if the molar masses are similar $(M_\mathrm{solvent}\approx M_\mathrm{solute}\approx \bar{M}),$ the expression can be lead to a common denominator:
$$n_\mathrm{tot} \approx \frac{m_\mathrm{solvent} + m_\mathrm{solute}}{\bar{M}}\tag{2}$$
The following is multiple choice question (with options) to answer.
All solutions contain at least how many substances? | [
"four",
"one",
"three",
"two"
] | D | All solutions contain at least two substances. |
SciQ | SciQ-6727 | evolution, molecular-biology, molecular-evolution, abiogenesis
The issue isn't actually as clear-cut as it may seem, since there is a very wide unknown space between what we consider the most archaic forms of life, and any entity that could plausibly arise via purely abiotic processes; every theory of abiogenesis does assume that a lot of the features we consider essential to life must have arisen after some kind of replication appeared, meaning those features would have evolved. So there definitely is some evolutionary biology involved in investigating abiogenesis, and maybe if we ever solve abiogenesis it will be folded into the ToE (like I said, the ToE is actually a complex set of theories and observations, not one single thing. So while our understanding of what the theory says and can say currently excludes abiogenesis, our understanding and definition of the theory could evolve). But we haven't, and it currently isn't.
You need to edit your question however, because it is completely unclear from the title or text that you are asking about abiogenesis. Your question sounds like it's about embryonic development or biochemistry. Those are the current instances we have of organisms forming; whatever processes were at work in creating the very first life, well for one thing maybe we wouldn't want to call whatever that was an "organism", but more to the point those processes cannot happen today. The atmosphere is wrong and too full of oxygen, there are organisms everywhere vaccuuming up whatever resources those original biochemical processes might have used, basically there is likely no chemical environment on modern Earth that's anything like the chemical environment life originated in.
To answer your question though, abiogenesis is currently an unsolved question, so no, Science does not have an explanation of how the first organisms formed. But if you want to have an idea of how things could have happened, what the challenges are in figuring things out, and what things Science currently considers likely or impossible, there is a lot of active research in the field and many different hypotheses. The Wikipedia page for Abiogenesis has a fairly comprehensive rundown on this.
This video describes one of them (my favorite and the first I've found actually convincing, I have no expertise whatsoever to base this on but I plug it anyway; if nothing else it gives an appreciation for what kind of things the researchers in this field look at when thinking abiogenesis) :
The following is multiple choice question (with options) to answer.
Life probably began where? | [
"the Sun",
"caves",
"rocks",
"oceans"
] | D | Life probably began in the oceans. No one knows exactly how or when. Life may have originated more than once. If life began before the Moon formed, that impact would have wiped it out. Then life would have had to originate again. Eventually conditions on Earth became less violent. The planet could support life. |
SciQ | SciQ-6728 | biochemistry, enzymes
Title: Can an enzyme be activated without allosteric inhibition or activation? Are there ways by which an enzyme may be activated or inhibited by non substrate molecules other than allosteric activation or inhibition? Apart from what Phototroph mentioned in their answer (competitive and non-competitive inhibition), an enzyme can be activated/inhibited via covalent modification of the protein (post-translational modification) such as phosphorylation by protein kinases (phosphorylation is the most common modification).
The following is multiple choice question (with options) to answer.
An enzyme is an organic catalyst produced by what? | [
"the liver",
"living cell",
"DNA",
"amino acid"
] | B | An enzyme is an organic catalyst produced by a living cell. Enzymes are such powerful catalysts that the reactions they promote occur rapidly at body temperature. Without the help of enzymes, these reactions would require high temperatures and long reaction times. The molecule or molecules on which an enzyme acts are called its substrates. An enzyme has an active site where its substrate or substrates bind to form an enzymesubstrate complex. The reaction occurs, and product is released:. |
SciQ | SciQ-6729 | human-biology, metabolism, toxicology
Title: How does the human body metabolize gasoline? A Chinese man has been drinking gasoline to relieve his pain for 25 years. How does the human body metabolize gasoline? Also, what are the side-affects to gasoline? Just to add an answer to the 'how does the body process gasoline?' portion of the question, the liver and kidney would be doing most of the work of removing the stuff from the system once it was absorbed in the digestive tract.
The liver does most of the processing of toxins and their removal from the blood and would tend to do the most work in removing hydrocarbons from gasoline. It has enzymes that oxygenate toxins (adds oxygens) which make them more soluable in the blood, usually less toxic, and also removable from the body by the liver or the kidney. In the case of gasoline the compounds are likely to be just as toxic.
The kidney works by actively filtering out excess water and mostly water soluable wastes like oxygenated hydrocarbons. Kidney damage occurs when gasoline is ingested in excess. This may be due to the toxicity of the gasoline, but also due to the compounds the liver is producing.
Gasoline will tend to be fat soluable too, so it will leave the system more slowly, even after being processed by the liver (benzene and toluene in gasoline will tend to become phenols which are quite toxic and fat soluable).
http://www.ncbi.nlm.nih.gov/pubmed/3379185
The following is multiple choice question (with options) to answer.
Gasoline is derived from which other liquid? | [
"water",
"liquid propane",
"oil",
"carbon"
] | C | Yes, we will use up all our gasoline eventually. Gasoline is derived from oil. Oil deposits were formed over hundreds of millions of years. They cannot be quickly replenished. Oil is an example of a nonrenewable resource. |
SciQ | SciQ-6730 | cancer, mutations
Here is another great paper that specifically addresses your question, linking increased cell division with the accumulation of both significant and insignificant mutations, which over time, lead to an accumulation of mutations needed for cancer to develop.
The following is multiple choice question (with options) to answer.
What is the disease in which cells grow out of control and form abnormal masses? | [
"HIV",
"cancer",
"bronchitis",
"diabetes"
] | B | Cancer is a disease in which cells grow out of control and form abnormal masses of cells. It is generally caused by mutations in genes that regulate the cell cycle. Because of the mutations, cells with damaged DNA are allowed to divide without limits. Cancer genes can be inherited. You can learn more about hereditary cancer by watching the video at the following link: http://www. youtube. com/watch?v=LWk5FplsKwM (4:29). |
SciQ | SciQ-6731 | special-relativity, waves, speed-of-light, acoustics, relative-motion
Title: Can sound be faster than 300m/s? If you sit in a car and it's driving $300{m \over s}$ and you clap your hands for a very very short sound, will it's wave be $600{m \over s}$ fast, because it adds the speed of the car?
Or will it be $300{m \over s}$ because it is just the point of origin that matters and from that point it travels away?
If the answer of the title question would be yes, that would also mean that light can also travel faster than speed of light, right? (I assume sound and lightwaves can be compared as both contains electeomagnetic waves) The speed of sound of 340 m/s is measured with respect to air. So here we can mention two cases:
If you are inside a car that is moving at 340 m/s in the highway and the windows are closed (so that the air inside the car is also moving at that speed), the sound of your clap will move at 680 mm/s with respect to the ground. This is because it moves at 340 m/s with respect to the air inside the car.
Imagine the same situation but with a car that has no roof nor windows. Then you, inside the car, will find that the air moves at 340 m/s backwards. If you clap in this situation the sound waves will move at 340 m/s in the air, but because this air moves at 340 m/s backwards you will see that the sound waves do not move at all.
The second case is exactly what happens in this picture:
When the supersonic aircraft is moving exactly at (or very near) the speed of sound (both with respect to the air), the waves travel at the same speed and they accumulate to form that peculiar cone.
In the case of light the case is different because light speed is 300000 km/s with respect to space itself. And you cannot move with respect to space, you move in space with respect to other things. Motion is relative. So the speed of light is the same for everyone independent of the speed of the observer (or the source).
The following is multiple choice question (with options) to answer.
What travels at a rate of 300,000 kilometers per second, or nearly instantaneously? | [
"light",
"gravity",
"air",
"sound"
] | A | The speed of sound in air is approximately , where is the temperature of the air in Celsius. The speed of light is 300,000 km/sec, which means it travels from one place to another on Earth more or less instantaneously. Let’s say on a cool night (air temperature Celsius) you see lightning flash and then hear the thunder rumble five seconds later. How far away (in km) did the lightning strike?. |
SciQ | SciQ-6732 | bond, orbitals, hybridization
( 82.71%) 0.9094* B 1 s( 33.25%)p 1.98( 65.98%)d 0.02( 0.76%)
( 17.29%) -0.4158* F 2 s( 36.24%)p 1.76( 63.62%)d 0.00( 0.14%)
The following is multiple choice question (with options) to answer.
When atomic orbitals hybridize, the valence electrons occupy these? | [
"newly developed orbits",
"newly created orbitals",
"newly created elements",
"expanded pathways"
] | B | When atomic orbitals hybridize, the valence electrons occupy the newly created orbitals. The Be atom had two valence electrons, so each of the sp orbitals gets one of these electrons. Each of these electrons pairs up with the unpaired electron on a chlorine atom when a hybrid orbital and a chlorine orbital overlap during the formation of the Be–Cl bonds. |
SciQ | SciQ-6733 | 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.
Roundworms feed on various things, one of them being decaying organic matter. doing this, they play an important role in what famous cycle? | [
"carbon cycle",
"water cycle",
"life cycle",
"soul cycle"
] | A | Roundworms may be free-living or parasitic. Free-living worms are found mainly in freshwater habitats. Some live in soil. They generally feed on bacteria, fungi, protozoans, or decaying organic matter. By breaking down organic matter, they play an important role in the carbon cycle. |
SciQ | SciQ-6734 | molecular-biology, cell-biology, proteins, cell-membrane
Title: What is meant by "opposing plasma membrane" with respect to cell adhesion molecules? I am reading the Handbook of Neurochemistry and Molecular Neurobiology and I am learning about cell adhesion molecules (CAMs) and I have come across the following:
CAMs are involved in homo‐ or heterophilic interactions with molecules
positioned on opposing plasma membranes, and such interactions are
referred to as trans‐interactions. In addition, CAMs are often
involved in homo‐ or heterophilic interactions with other
membrane‐associated molecules positioned in the same plasma membrane.
Such membrane‐lateral interactions are referred to as
cis‐interactions.
I know that cell adhesion molecules are proteins mediation cell-cell or cell-extracellular matrix interactions. However, in the above excerpt from the book in the following statement: CAMs are involved in homo‐ or heterophilic interactions with molecules positioned on opposing plasma membranes, I am not sure what exactly is meant by "opposing plasma membranes". I think that this refers to the plasma membrane of a neighbouring cell the CAM is interacting with, however I am not fully certain.
Any insights are appreciated. Opposing means facing each other, so the two outer surfaces can interact. Like two opposing armies.
I found an article:
"Pharmacology of cell adhesion molecules of the nervous system"
at
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2644493/
doi: 10.2174/157015907782793658
"...CAM-induced intracellular signalling is triggered via homophilic (CAM-CAM) and heterophilic (CAM - other counter-receptors) interactions..."
The following is multiple choice question (with options) to answer.
In preparation for phagocytosis, a portion of the inward-facing surface of the plasma membrane becomes coated with a protein called clathrin, which stabilizes this section of what? | [
"membrane",
"nuclei",
"particles",
"mitochondria"
] | A | In preparation for phagocytosis, a portion of the inward-facing surface of the plasma membrane becomes coated with a protein called clathrin, which stabilizes this section of the membrane. The coated portion of the membrane then extends from the body of the cell and surrounds the particle, eventually enclosing it. Once the vesicle containing the particle is enclosed within the cell, the clathrin disengages from the membrane and the vesicle merges with a lysosome for the breakdown of the material in the newly formed compartment (endosome). When accessible nutrients from the degradation of the vesicular contents have been extracted, the newly formed endosome merges with the plasma membrane and releases its contents into the extracellular fluid. The endosomal membrane again becomes part of the plasma membrane. Pinocytosis A variation of endocytosis is called pinocytosis. This literally means “cell drinking” and was named at a time when the assumption was that the cell was purposefully taking in extracellular fluid. In reality, this is a process that takes in molecules, including water, which the cell needs from the extracellular fluid. Pinocytosis results in a much smaller vesicle than does phagocytosis, and the vesicle does not need to merge with a lysosome (Figure 5.21). |
SciQ | SciQ-6735 | biochemistry, plant-physiology, plant-anatomy
Title: Why do plants store energy as carbohydrates and not as fats? In my introductory biology class, we are learning about biomolecules. The textbook says fats are a more efficient energy store than carbohydrates.
So my question is - why would plants store their energy as carbohydrates and not as fats, if fats are a more efficient energy store? There are quite some reasons for why plants prefer carbohydrates for energy storage rather than fats. I will reach some of them one at a time.
The following is multiple choice question (with options) to answer.
What is the main form of energy storage in plants? | [
"liquid",
"dioxide",
"starch",
"nitrogen"
] | C | Many simple sugars can combine by repeated condensation reactions until a very large molecule is formed. A polysaccharide is a complex carbohydrate polymer formed from the linkage of many monosaccharide monomers. One of the best known polysaccharides is starch, the main form of energy storage in plants. Starch is a staple in most human diets. Foods such as corn, potatoes, rice, and wheat have high starch contents. Starch is made of glucose monomers and occurs in both straight-chain and branched forms. Amylose is the straight-chain form and consists of hundreds of linked glucose molecules. The branched form of starch is called amylopectin. In the small intestine, starch is hydrolyzed to form glucose. The glucose can then be converted to biochemical energy or stored for later use. |
SciQ | SciQ-6736 | botany, ecology, energy
Title: Why do plants create enough energy for the entire ecosystem? In my environmental class, we were recently learning about the $10\%$ law that basically says only $10\%$ of the energy goes from one trophic level to the next.
This got me thinking about why energy flows from one level to the next. Specifically, why do plants create enough energy for the entire ecosystem? Wouldn't they do fine without us, and wouldn't that save them the work of creating all that excess energy? Plants collect energy for themselves via photosynthesis, not for others.
It is used for it's own growth and survival.
It's energy is then redistributed to other organisms when either the plant dies and decomposes or when it is consumed. Many organism cannot collect their energy like plants do, and thus must feed on organisms (like plants) that are able to collect and store energy. This is in many cases detrimental to the plant (it should be intuitive why being eaten might be bad), and many, many plants do have traits to discourage other organisms from eating them (plants with toxins, thorns, etc.).
The following is multiple choice question (with options) to answer.
Something supplied by nature that helps support life, including ecosystems as well as minerals and fossil fuels, is called a what? | [
"fluid resource",
"natural resource",
"visible resource",
"artificial resource"
] | B | A natural resource is something supplied by nature that helps support life. When you think of natural resources, you may think of minerals and fossil fuels. However, ecosystems and the services they provide are also natural resources. Biodiversity is a natural resource as well. |
SciQ | SciQ-6737 | redox, oxidation-state
Title: Terminology of redox reactions: which species are the oxidizing and reducing agents? I've got a question regarding 'notation' for redox reactions. Suppose you are asked to identify the oxidizing and reducing agents for a simple reaction like this one:
$$\ce{Cl2(aq)}+\ce{2KI(aq)} \longrightarrow \ce{2KCl(aq)}+\ce{I2(aq)}$$
Now are you supposed to say $\ce{Cl}$ is the oxidizing agent or $\ce{Cl2}$? Also, is $\ce{KI}$ the reducing agent or $\ce{I}$ or $\ce{I^-}$?
By the way, if you were instead asked to identify which species got oxidized, would you again say that $\ce{KI}$ is oxidized or $\ce{I}$ or $\ce{I^-}$? Ignoring spectator ions,
$\ce{Cl2 +2 I- ->2Cl- +I2}$
So, $\ce{Cl2}$ is the oxidant and $\ce{I-}$ is the reductant.
The following is multiple choice question (with options) to answer.
Initial substances are called reactants, and the final substances are called what? | [
"exports",
"products",
"reactors",
"imports"
] | B | H2 + O2 → H2O This is an example of a chemical equation, which is a concise way of representing a chemical reaction. The initial substances are called reactants, and the final substances are called products. Unfortunately, it is also an incomplete chemical equation. The law of conservation of matter says that matter cannot be created or destroyed. In chemical equations, the number of atoms of each element in the reactants must be the same as the number of atoms of each element in the products. If we count the number of hydrogen atoms in the reactants and products, we find two hydrogen atoms. But if we count the number of oxygen atoms in the reactants and products, we find that there are two oxygen atoms in the reactants but only one oxygen atom in the products. What can we do? Can we change the subscripts in the formula for water so that it has two oxygen atoms in it? No; you cannot change the formulas of individual substances because the chemical formula for a given substance is characteristic of that substance. What you can do, however, is to change the number of molecules that react or are produced. We do this one element at a time, going from one side of the reaction to the other, changing the number of molecules of a substance until all elements have the same number of atoms on each side. To accommodate the two oxygen atoms as reactants, let us assume that we have two water molecules as products:. |
SciQ | SciQ-6738 | electrons, charge, quasiparticles, leptons
Title: How do electrons get a charge? Electrons belong to a group of elementary particles called leptons. There are charged and neutral leptons. And electron is the charged one. But how come it got charged?
The negative or positive charges were assigned by convention. But it is a fact that electrons are charged. My question is why electrons? and not neutrons?
Also while reading http://en.wikipedia.org/wiki/Electron, I saw that "Independent electrons moving in vacuum are termed free electrons. Electrons in metals also behave as if they were free. In reality the particles that are commonly termed electrons in metals and other solids are quasi electrons, quasiparticles, which have the same electrical charge, spin and magnetic moment as real electrons but may have a different mass ( or Effective mass - extra mass that a particle seems to have while interacting with some force )."
What does this mean? Your question touches the question of ontology in particle physics. Historically we are used to be thinking of particles as tiny independent entities that behave according to some laws of motion. This stems from the atomistic theory of matter, which was developed some two thousand years ago from the starting point of what would happen if we could split matter in ever smaller parts. The old Greeks came to the conclusion that there had to be a limit to that splitting, hence the atom hypothesis was born.
This was just a philosophical idea, of course, until around the beginning of the 19th century we learned to do chemistry so well that it became obvious that the smallest chunks that matter can be split into seemed to be the atoms of the periodic table. A hundred years later we realized that atoms can be split even further into nuclei and electrons. What didn't change was this idea that each chunk had its own independent existence.
This idea ran into a deep crisis during the early 20th century when we discovered the first effects of quantum mechanics. It turns out that atoms and nuclei and electrons do not, at all, behave like really small pieces of ordinary matter. Instead, they are behaving radically different, so different, indeed, that the human imagination has a hard time keeping up with their dynamic properties.
The following is multiple choice question (with options) to answer.
What were the electrons initially called? | [
"cathode rays",
"gamma rays",
"polymer rays",
"plasma rays"
] | A | Negatively charged and has a very small mass compared to the mass of other subatomic particles. Electrons were initially called cathode rays. |
SciQ | SciQ-6739 | newtonian-mechanics, energy, work
Title: Types of energy and work I am learning about energy and work, and am a beginner to this topic. Energy is defined as the ability to do work. In some cases, the ability to do work directly follows the type of energy. For instance, heat energy can be used to do work through isothermal expansion of gas, for instance.
Is there a relationship/concept between how easy it is to get a type of energy to do work? Some types of energy might make them more suitable to do work, whereas others might involve a more indirect/contrived route. Energy defined as the ability to do work; this does not mean that only work is done, it means that work can be done.
Here is an expanded definition that should help.
The energy of a system is a property of the system that is increased (decreased) by the following mechanisms:
work done on (or done by) the system from its surroundings
heat added to (or removed from) the system from its surroundings
mass transfer into (or from) the system to its surroundings.
"How easy it is to get a type of energy to do work" depends how the system interacts with the surrounding.
For example, if a system comprised of a gas has a higher pressure than its surroundings and can move a boundary (say a piston), the system can lose energy by doing work on the surroundings as the gas expands. Or if the gas is in a closed container (fixed volume) and has a higher temperature than its surroundings, the gas can lose energy by transferring heat to the surroundings. A liquid can have a decrease in its energy, with a decrease in its temperature, by evaporation (mass transfer from the liquid).
The details of energy transfer is addressed by the laws of thermodynamics (e.g., the first and second laws).
The following is multiple choice question (with options) to answer.
What is the type of energy that involves movement? | [
"molecular energy",
"thermal energy",
"light energy",
"mechanical energy"
] | D | All of the examples of potential energy described above involve movement or the potential to move. The form of energy that involves movement is called mechanical energy. Other forms of energy also involve potential energy, including chemical energy and nuclear energy. Chemical energy is stored in the bonds between the atoms of compounds. For example, food and batteries both contain chemical energy. Nuclear energy is stored in the nuclei of atoms because of the strong forces that hold the nucleus together. Nuclei of radioactive elements such as uranium are unstable, so they break apart and release the stored energy. |
SciQ | SciQ-6740 | 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 do sharks use to secrete salt to assist in osmoregulation? | [
"bladder gland",
"blood gland",
"rectal gland",
"ceramic gland"
] | C | animals exposed to similar levels of urea. Sharks are cartilaginous fish with a rectal gland to secrete salt and assist in osmoregulation. |
SciQ | SciQ-6741 | virus, life, philosophy-of-science
Title: Is there any definition of life which makes viruses undeterminable? There are many different definitions of life (RNA, something that comes through evolution) but not one I have seen which could not determine wheter viruses are living things (even though there are many definitions both for YES and NO). Are there any such definitions (I'm looking for cases where it's really fundamental debate, not only struggling for the correct dictionary definition)?
Thank you. Your last sentence is the key: defining life really is just finding a dictionary definition that we can agree upon. Biology is something that defies discrete definitions at times: "What is it to be alive?" "What is a species?" maybe even "What is the wild type allele of a gene?"
I would recommend not looking at viruses as a challenge to determine if they are alive or not so much as an excellent opportunity to discuss what we think are important characteristics of life.
Life can alternately be described as:
"Comprised of self-replicating cells" (a paraphrase of the "Cell Theory of Life"
or
As things that embody at least most of the following characteristics:
1. Self-Replicating
2. Metabolizing
3. Growing
4. Showing signs of adaptation
5. Being organized
6. Respond to their environment
7. Being comprised of cells
I like to think that we should focus on extraterrestrial forms when we define life. i.e. what would we want to see in an extraterrestrial in order to call it 'life'? While some are troubled by calling viruses alive here on earth, the same people might be willing to say that we have found extraterrestrial life on another planet if it was similar (granted, it's hard to imagine this kind of life existing without a host...)
as an aside: You might also ask whether this question is fit for this stack as it can not be supported by literature references (at least none that would actually support a conclusion). So should this be posted as 'Biology' or 'Philosophy'?
The following is multiple choice question (with options) to answer.
Why do viruses not belong to any domain of life? | [
"they are nonliving",
"they are too mature",
"they are mortal",
"they are immortal"
] | A | Which of the three domains of life do viruses belong to? None. Why? Viruses are usually considered to be nonliving. Viruses do not meet most of the criteria of life. They are not even made of cells. |
SciQ | SciQ-6742 | gene-expression, epigenetics, nucleic-acids, dna-methylation, nucleotide
Title: DNA methylation and the validity of the definition of epigenetics I am currently studying a textbook that presents the following definition of epigenetics:
Epigenetics is defined as heritable changes in gene expression without changes in the DNA sequence.
The authors then claim the following:
DNA methylation is a stable and inheritable epigenetic mark. This genetically programmed modification is almost exclusively found on the 5' position of the pyrimidine ring of cytosines (5mC) adjacent to a guanine.
Given these two excerpts, it seems somewhat contradictory to define epigenetics as heritable changes in gene expression without changes in the DNA sequence. After all, the DNA sequence is comprised of nucleotides, and it is these nucleotides that are modified during methylation (for instance, the addition of the methyl group on the 5' position of the pyrimidine ring of cytosines adjacent to a guanine), right? So, is it not technically true that the DNA sequence is changed? Or is what they're saying that, although the nucleotide is changed (such as in DNA methylation), the base pairs are unchanged (I'm unsure if this is true, just hypothesising)?
I would greatly appreciate it if people would please take the time to clarify this. A methylated nucleotide is the same nucleotide, for the purposes of base-pairing events. The methylated base will be paired with its Watson-Crick opposite after replication, for instance (and methylation will even persist after replication).
The following is multiple choice question (with options) to answer.
What is a change in the sequence of bases in dna or rna called? | [
"radiation",
"evolution",
"mutation",
"infection"
] | C | A change in the sequence of bases in DNA or RNA is called a mutation . Does the word mutation make you think of science fiction and bug-eyed monsters? Think again. Everyone has mutations. In fact, most people have dozens or even hundreds of mutations in their DNA. Mutations are essential for evolution to occur. They are the ultimate source of all new genetic material - new alleles - in a species. Although most mutations have no effect on the organisms in which they occur, some mutations are beneficial. Even harmful mutations rarely cause drastic changes in organisms. |
SciQ | SciQ-6743 | inorganic-chemistry, alloy
Title: If alloys are homogeneous mixtures, why can't we separate their components? An alloy is a material composed of two or more metals or a metal and a nonmetal. And, they are usually formed by heating the elements to their melting points, and then cooling them, so that the components mix. Now, why doesn't this works backwards i.e. if we heat the alloy again to melting point of their constituents, and they should separate? Once the alloy has been formed the atoms from the different metals will have shared there electrons with each other and come to an equilibrium. In this state the metal atoms have formed a complex structure which has a different reactivity or properties than each individual metal did in its original form .
The following is multiple choice question (with options) to answer.
Metallic solids are composed entirely of which atoms? | [
"metals",
"metallic",
"toxic",
"organic"
] | B | Metallic solids are composed entirely of metallic atoms. In other solid structures, the electrons involved in bonding tend to be localized, or fixed in place in the covalent bonds. However, the electrons in metallic bonds are delocalized over the entire crystal. The fact that the electrons are free to move between different atoms causes metallic solids to be very good conductors of electricity. |
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