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Jul
25
comment Do the enzymes and compounds in saliva help with stain removal?
Amylase doesn't break down proteins. It breaks down amylopectin -- a type of starch (sugar) molecule. Proteins are broken down by proteases (not found in saliva or semen), and many available stain removers use proteases.
Jul
10
comment An obscure reference to a “golden vein”
At least one other person agrees with you: books.google.com/…
Jul
7
comment Is the immune system suppressed during sleep?
I don't have the time for a full answer, so I may come back, but generally 'no'. There is a difference between hibernation (a reduction in metabolic rate to survive prolonged periods of fasting) and sleeping. Humans do not hibernate, and when we are asleep the body doesn't try to save energy. Our brains go through REM sleep, which is just as active as waking hours, our organs -- especially dermal and muscle tissues -- amp-up their repair mechanisms while sleeping. Given that prolonged poor and/or lack of sleep significantly lengthens illnesses, the immune system should be very active.
May
15
comment What are the effects of long-term liquid breathing?
@HDE226868 -- One thing that absolutely must be said that wasn't addressed is this: All of those human studies used external pumps to move the fluid. Mammalian diaphragms are not designed to move a liquid medium more than a handful of times. They will literally tear themselves to shreds very, very quickly.
May
13
comment What recovers normal polarisation after hyperpolarisation?
Can't give a full comment at the moment, but... Na+ and K+ have different electrochemical equilibriums, and in addition to the Sodium-Potassium Pump there are many porins that act as passive diffusion routes to re-establish the cell's preferred equilibrium.
Apr
29
comment Do we have fundamental conflict in biology?
@Remi.b -- More cells = more cell divisions required in the first place. Whale cells are not orders of magnitude larger than humans, despite being orders of magnitude larger as an organism. Since the vast majority of cells have some turnover, having more could also mean a hire rate of division even if the time it takes is higher. Peto's paradox looks fine (to me), but it does point out that DNA mutations do not always result in cancer. An extra stop-check prior to cell division seems to have a tremendous effect on cancers if you look at Naked Mole Rats. ;-)
Apr
19
comment Why did the Brain develop in the front in most organisms?
@aandreev -- They co-evolved. As brains became more complex and bigger, there needed to be a better place to store them. Thick bones aren't very spacious. Hollow bones aren't very protective. The compromise for organisms evolving a larger brain was the skull: A hollow, encapsulating bone that can also be very dense (especially among goats, bovines, etc.). It's also a design that means there's only one area to protect instead of every single thick bone in your body.
Apr
4
comment Core Biological concepts explained to a Computer Scientist?
@poka.nandor Thanks. :-)
Feb
25
comment Baby birds hair and mammal hair is a convergent evolution?
Fledglings do not have hair, but "down" -- a very, very fine type of feather used to insulate the chicks (and convergent in purpose with mammalian hair there).
Feb
6
comment Does long term use of antibiotics in humans actually lead to a greater risk of infection?
Not usually in the individual, but in a population, improper antibiotic use can lead to resistant strains and more infections. Improper use usually means stopping therapy short and not using all the pills, using antibiotics for diseases they cannot help with, or very-long-term use in a healthy individual. Antibiotic resistance is basic a probability function, with the increase exposure to the antibiotics increasing the probability resistance will develop. Regimes are designed so that bacterial populations stay isolated/small and the chance for resistance remains small.
Jan
22
comment Is there any tree or other plant that produces a new crop in fast cycles?
@twelve -- I'd suggest something like gardening.stackexchange.com for people more knowledgeable than I. I'm a novice gardener, but from what I recall most people would need 2-3 basil plants to cover moderate to heavy use of the herb in their cooking from early spring through early fall (in climates where temperatures drop below freezing).
Jan
22
comment Is there any tree or other plant that produces a new crop in fast cycles?
Several harvests occur from most agricultural plants, most have 2-3 harvest periods per year, with a few exceptions. I'm not aware of any plant that produces a new crop every month; the closest I can think of would be herbs like Basil -- but that's because it produces continuously until it goes dormant.
Jan
22
comment True or false & fill in the blanks
@canadianer -- I agree, the nomenclature is pretty arbitrary and can be misleading. Thanks for bringing it up. :-)
Jan
22
comment True or false & fill in the blanks
@canadianer -- Yeah, but the nomenclature conventions make "polypeptides" to usually 3-5 peptides chained together. Before is "dipeptide" and after can get up to "oligilopeptide" IIRC.
Jan
18
comment how do macrophages have the capacity to digest pathogen in opsonization
There are multiple mechanisms to induce phagocytosis by macrophages. One includes B-cell antibodies (specifically the Fc region) and another includes chemokines emitted by local cells that can also induce phagocytosis. I do not have my material with me at the moment, but the short answer is: Macrophages can do both. They can eat pathogens without antibody stimulation, but antibodies can also stimulate them into action.
Jan
16
comment Father with mutated mtDNA- why isn't his offspring at risk?
@anongoodnurse "Paternal Inheritance of Mitochondrial DNA in Mice" - Nature 1991. The truth is that some paternal mtDNA is passed along, but the undergrad level generalization is that "no" paternal mtDNA is passed because the amount is practically non-existent outside of rare cases. In those rare cases then mtDNA can cause metabolic issues, like the 28 year old case study by Scwhartz in 2002.
Oct
2
comment How long does a signal from the brain take to reach the limbs?
@Christian - Roughly half, I'd assume. A full reflex arc is from a sensory neuron to the spinal column and back out to the muscles. The difference is probably due to length and the added junctions.
Oct
1
comment How long does a signal from the brain take to reach the limbs?
@shigeta - They're some overlap (the Vagus is a good example), but the function maps to the fiber type fairly well since space is the primary limiting factor for the peripheral system. However, I'll admit I haven't refreshed myself of the topic for a while, so it's possible the ratios are less strict than I believe.
Sep
25
comment What is a catalytic domain of an enzyme?
AFAIK MattDMo is correct. The catalytic site is the active site where the reaction takes place that triggers the conformation change. He is also correct about there being nearly infinite potential catalytic site designs.
Sep
7
comment Why do we absorb vitamins better from whole foods than from pills?
@user6035 - Yes, you could eat an artificial diet of macronutrients and micronutrients that would satisfy your biochemical needs. It would probably be "healthy" in that you would probably continue to live without issues you weren't already predisposed to. How other chemicals and compounds contribute to our health are unknown (think antioxidants), but have the potential to contribute significantly. However, please consult medical professionals for further info if you intend to pursue this. Due to genetic variation your body might have greater or lesser needs than the recommendations.