The study of chemistry within the scope of biology: the compounds that occur and the reactions involving them in living organisms.

learn more… | top users | synonyms

3
votes
1answer
248 views

How does temperature influence the rate of protein degradation?

For computer modeling purposes, I am looking for some referenced quantitative measurements of the effect(s) of temperature on biochemical reactions. Question In particular, my question is: How does ...
68
votes
4answers
42k views

Why is uracil used in RNA rather than thymine?

What is the advantage gained by the substitution of thymine with uracil? I have read previously that it is due to thymine being "better protected" and therefore more suited to the storage role of ...
59
votes
4answers
8k views

Why 22 amino acids instead of 64?

This question got me thinking about amino acids and the ambiguity in the genetic code. With 4 nucleotides in RNA and 3 per codon, there are 64 codons. However, these 64 codons only code for 22 ...
14
votes
3answers
2k views

What implications has the missing 2'-OH on the capability of DNA to form 3D structures?

The chemical difference between RNA and DNA is the missing 2'-hydroxyl group in the nucleotides that build DNA. The major effect of that change that I know of is the higher stability of DNA compared ...
38
votes
3answers
1k views

Can scientists create totally synthetic life?

This particular question has been of a great deal of interest to me, especially since it dives at the heart of abiogenesis.
9
votes
2answers
758 views

Why does Hunger lead to the aggressive behavior?

I have observed that frequently when people are hungry; they tend to get angry more easily on pointless issues. Does this mean that our fight or flight response is more active when a person is hungry? ...
7
votes
1answer
361 views

What is the molecular basis of hangovers?

Well, most of us have experienced the wonderful feeling of the dreaded hangover. How does it work exactly? I imagine it has something to do with dehydration but what are the underlying mechanisms? ...
18
votes
4answers
3k views

Why are there exactly four nucleobases in DNA?

Does someone know why DNA is composed of four nucleobases? In particular, is there an explanation for the number? Why four and not two, or eight?
5
votes
1answer
581 views

What causes humans to be sleepy?

Is there a hormone or group of hormones that regulates when we feel sleepy late at night, or in the morning? Or is sleepiness caused by some other non-hormonal mechanism? (e.g. pure psychological, ...
3
votes
1answer
82 views

Dehydration by a tea, coffee, beer etc

For the long time I am trying to find out if the following is truth: They say that some beverages dehydrates. I heard that about tea (sometimes green, sometimes black, sometimes both), coffee, beer ...
3
votes
2answers
900 views

Is there a difference between polarity and hydrophobicity?

From literature the two terms seem to be interchangeable when discussing protein domains and motifs. But biochemically, what are the specific differences between these two terms? For example what is ...
1
vote
1answer
79 views

Influence of temperature on protein binding and decay rates

For computer modeling purposes, I am looking for some referenced quantitative measurements of the effect(s) of temperature on the dynamic of biochemical reactions. Question In particular, my ...
50
votes
4answers
32k views

Death because of distilled water consumption

One of my friends said that I would die if I drank distilled water (we were using it in a chemistry experiment) I gave it a go and surprisingly did not die. I did a bit of Googling and found this ...
14
votes
1answer
2k views

Why does hair turn grey or white, and why does it happen later for some?

The question is pretty simple: what is happening molecularly when hair turns grey or white? I would imagine that it is due to the lack of a particular compound. I'm also interested in why some ...
9
votes
2answers
160 views

What role does a protein's size have on protein-protein interactions?

Protein-protein interactions are when two or more proteins bind together, possibly for some important biological function. Recently, I'm starting to look more into proteins, and in particular, ...
8
votes
1answer
6k views

Why is ATP the preferred choice for energy carriers?

Why is ATP the most prevalent form of chemical energy storage and utilization in most cells?
6
votes
1answer
213 views

What exactly makes bananas go brown?

I know that often oxidation processes are mentioned when referring to the color change from yellow to brown in bananas (specifically: those that you get everywhere in supermarkets, with no seeds). ...
9
votes
1answer
487 views

Does DNA react in all of the ways most other acids do?

As I understand it from my basic chemistry, there are some fundamental reactions that exist between any acid and other substances for example acid-base reactions that form a salt, and the existence of ...
6
votes
1answer
4k views

HDL- and LDL-cholesterol

Why exactly are HDL-cholesterols good for us and LDL-cholesterols not. I know LDL-cholesterols cause Atherosclerosis and that HDL-cholesterols removes the excess of LDL-cholesterols, but from a ...
5
votes
3answers
1k views

How does protein denaturation work?

I was wondering how protein denaturation works. Are there covalent bonds, such as disulfide bridges involved, or is it based purely on non-covalent bonds such as hydrogen bonds? Why is denaturation ...
4
votes
2answers
545 views

In biosynthesis of cysteine and methionine, where does the sulfur come from?

Methionine and Cysteine are the two amino acids containing sulfur. According to wikipedia, cysteine is built from methionine. However, the wikipedia also claims that methionine is synthesized from ...
4
votes
3answers
2k views

Histidine aromaticity

I understand that the imidazole ring in histidine is aromatic. I also realize that it retains it's aromaticity when protonated. I am wondering why it is not mentioned at all in basic text books such ...
3
votes
1answer
56 views

What is the film that covers the tongue?

What is the film that covers the tongue in the mornings, even after brushing the teeth and tongue the night before and why does it have color variations? Do the different colors mean anything?
3
votes
2answers
110 views

Humidity for wood rotting

If I put a piece of wood in a humid environment (basically humid air), it will start to rot. Does the humidity influence the rotting speed, and if so, what is the relation between the rotting speed ...
2
votes
1answer
737 views

Is there any advantage of having a mitochondria for aerobic respiration?

If we consider the pathway of breakdown of glucose which includes glycolysis, the citric acid cycle and the electron transport chain, all these processes takes place in some prokaryotes and ...
2
votes
1answer
96 views

Formation of ammonia from air and moisture

On extended bicycle trips I sometimes slept under a plastic sheet, which helped with mosquitoes on hot nights. But there was a noticeable build-up of ammonia which made this almost impossible for more ...
1
vote
1answer
78 views

Examples of how the presence or absence 2'-hydroxyl groups influence physicochemical properties of DNA and RNA

I know, for instance, that RNA is much more succetible to alkaline hydrolysis than DNA and this difference is determined by the presence of 2'-hydroxyl group in ribose. I have also heard that "DNA is ...
1
vote
1answer
36 views

Dehydration from caffeine, alcohol and other

Tea, Coffee, Beer, Coke etc… I wonder if the benefit from amount of fluid we get from them is bigger or smaller then the handicap of dehydration. In other words it is worth to drink them if we want ...
1
vote
1answer
69 views

How is the rate of transcription influenced by temperature?

How is the rate of transcription influenced by temperature? More precisely, I am looking for an article who quantitatively measured the rate of transcription of an "average gene" and show how this ...
22
votes
1answer
618 views

How, on a physical level, does ATP confer energy?

When ATP is used as the energy currency to make, say, reaction X + Y → Z happen, is what happens on a physical level down at the molecular scale that during the reaction ATP + H2O → ADP + Pi ...
20
votes
1answer
312 views

Evolutionary origin and exogenous cues of ~28 day infradian rhythm?

The most obvious example of an approximately monthly biological cycle is the human menstrual cycle. My questions are the following: Is it known when and where this cycle or one like it arose? What ...
20
votes
3answers
311 views

How crowded is the bacterial cell?

I was wondering what is the protein concentration in an E. coli cell. When studying enzyme kinetics and activity in vitro, I would argue that the substrate and enzyme concentrations resemble those in ...
15
votes
4answers
5k views

Why we have no enzyme to digest cellulose?

As we know, cellulose is the most abundant polysaccharide in nature. Why don't we have any enzyme to digest cellulose?
15
votes
2answers
5k views

Why is glucose our primary source of energy?

Is there any evolutionary reason for glucose being the "main" molecule used as a source of energy, beginning with glycolysis and subsequently cellular respiration (after being converted to two ...
8
votes
1answer
338 views

How do the pharmacodynamics of the NSAIDs differ and are there “resistant” COX phenotypes?

I know that the non-steroidal anti-inflammatory drugs (e.g., aspirin, ibuprofen, naproxen) affect the enzymes cyclooxygenase (types I and II). Is there any difference in the degree to which these ...
5
votes
1answer
103 views

enzymes that stabilize DNA loops

As a follow-up of a previous question, I would like to know what enzymes or protein complexes have been used to manipulate DNA samples into stabilizing DNA loops. I have read that cohesin is one of ...
2
votes
1answer
598 views

What can cause the bloating in high protein diet of Whey proteins?

I am thinking what can cause the swelling of gastrointestinal system i.e. bloating after high protein diet of Whey proteins. Liver does breaks those proteins to branched chain amino acids (BCAA), ...
33
votes
5answers
7k views

What does the human body use oxygen for besides the final electron acceptor in the electron transport chain?

My biology teachers never explained why animals need to breathe oxygen, just that we organisms die if we don't get oxygen for too long. Maybe one of them happened to mention that its used to make ATP. ...
20
votes
4answers
3k views

Where does the 'C' in exhaled CO₂ mostly come from?

When a human being exhales CO₂, what is, by the numbers, the main source of carbon atoms exiting the body in this way? I mean what class of cells, or which tissues are the biggest on a pie chart of ...
10
votes
1answer
4k views

Why does Rigor Mortis occur after death?

After someone dies they become stiff, this is termed Rigor Mortis and happens because the cells run out of ATP (I think). But why do the cells need it to remain flexible?
7
votes
1answer
2k views

Why does the heart use lipids (and not glucose)?

Fetal hearts use glucose as their primary metabolic substrate. Adult hearts use free fatty acids, which are less efficient (require more $O_2$ to synthesize the same amount of ATP); however, during ...
7
votes
1answer
198 views

Decreasing the alcohol proof and faster in hangover, why?

My russian friend says that the USSR agents used/use the trick that they offered the victim first vodka and then last wine. I have noted that this puts you faster to hangover: decreasing the alcohol ...
4
votes
1answer
146 views

What is the physiological difference between cortisone and cortisol?

There is only hydrogen bond different. Cortisol is synthesized by our body, while cortisone is given to the patient. Why you cannot give cortisol directly to the patient? I think the reason is ...
4
votes
2answers
216 views

Effect of testosterone hormone on cell signalling and behaviour?

A steroid, testosterone was injected in female body which led to development of secondary sexual characters but these characters were not developed over night (Response was very slow). What could be ...
4
votes
2answers
403 views

Are there dangers to Teflon and aluminium cookware?

I've been reading some articles on the internet about dangers of Teflon and aluminium to the body. My family say I'm just exaggerating the situation, and maybe I am, though I'm not sure because not ...
14
votes
1answer
4k views

How does a plant grow before photosynthesis is possible?

During photosynthesis, a plant translates CO2, water and light into O2. I assume the carbon C is further used for the growing process. I wonder how the plant grows before the time where photosynthesis ...
13
votes
1answer
361 views

Solubility of DNA in water

This would seem to be an easy to answer question, but I was unable to find an answer (in g/L) for generic double-stranded DNA or plasmid neither on Google nor on BioNumbers. I would expect the ...
13
votes
2answers
1k views

Is the EC50 of an activating protein for an enzyme a good indicator for the binding affinity Kd?

We work with a membrane protein system where measuring the affinity between the enzyme and the upstream activating protein has been difficult, and when measured in detergent solution, it is almost 100 ...
12
votes
2answers
424 views

Are there any plants that fix their own nitrogen?

I know that most nitrogen is fixed through industrial processes and bacterial symbiotic relationships. However, are there any plants that can fix their own atmospheric nitrogen?
11
votes
1answer
729 views

How do I get the current “camera position” in PyMol so I can reuse it in scripts?

I have a few protein models I want to take pictures of with various ligands bound. It would be nice if I could do it from the same "position", but the only way I can figure out to repeat the same ...