Questions tagged [biochemistry]

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

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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 ...
Remi.b's user avatar
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Why is thymine rather than uracil used in DNA?

What is the advantage gained by the substitution of thymine for uracil in DNA? I have read previously that it is due to thymine being "better protected" and therefore more suited to the storage role ...
Rory M's user avatar
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Why 20 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 20 amino ...
Daniel Standage's user avatar
35 votes
3 answers
61k 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?
hello all's user avatar
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Human Digestion of Cellulose?

Most animals can digest the cellulose in grass because of the anaerobic bacteria called Fibrobacter succinogenes living in their rumen (gut). The bacteria produces the enzyme cellulase and is ...
Crozier's user avatar
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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 people'...
LanceLafontaine's user avatar
21 votes
2 answers
2k views

What inactivates pepsin in infants?

In infants, rennin helps in digestion of milk. Pepsin is also present in their stomach. Why do infants need rennin for milk digestion, at the first place? Why does pepsin not act on the milk ...
Mesentery's user avatar
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What is/are the molecular differences between HDL and LDL cholesterol?

Why exactly is HDL-cholesterol good for us and LDL-cholesterol bad for us. It has been well-established that LDL-cholesterol is associated with atherosclerosis and that HDL-cholesterol helps remove ...
JohnPhteven's user avatar
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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 ...
Remi.b's user avatar
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84 votes
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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 ...
The-Ever-Kid's user avatar
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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.
Larian LeQuella's user avatar
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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  &...
mring's user avatar
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What is a coupled reaction and why do cells couple reactions?

I was wondering what exactly a coupled reaction is and why cells couple them. I read the wikipedia article as well as several others, such as life.illinois.edu but I still don't get it. Could ...
Snakes and Coffee's user avatar
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1 answer
554 views

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 ...
Hans-Peter Stricker's user avatar
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1 answer
13k views

Can plants produce oxygen at night (without light)?

I accidentally clicked on a "Top n X's that Y" result in google and found Top 9 ...
uhoh's user avatar
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Why don't the heads of phospholipid bilayers repel hydrophobic molecules?

What I Think I Know: Hydrophilic and hydrophobic things repel each other. Since the cell membrane contains hydrophobic tails, it is difficult for hydrophilic molecules to pass through the cell ...
Taylor's user avatar
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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). ...
tschoppi's user avatar
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Can the human body create glucose out of fat?

I read conflicting views about whether or not the human body can create glucose out of fat. Can it?
Christian's user avatar
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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 ...
Remi.b's user avatar
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59 votes
10 answers
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Why are there no organisms with metal body parts, like weapons, bones, and armour? (Or are there?)

Reading this question, Why are there no wheeled animals?, I wondered why no organisms seem to make use of the tensile and other strengths of metal, as we do in metal tools and constructions. I am ...
Cerberus's user avatar
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41 votes
5 answers
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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. ...
Gordon Gustafson's user avatar
25 votes
2 answers
19k views

Do all proteins start with methionine?

Start codon AUG also codes for methionine and without start codon translation does not happen. And even the ambiguous codon GUG codes for methionine when it is first. So does this mean that all ...
sreekara's user avatar
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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 ...
Mad Scientist's user avatar
14 votes
2 answers
3k 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 ...
gkadam's user avatar
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12 votes
1 answer
304 views

What's happening in the "C" and "T" stripes of a covid test kit?

I have a COVID home test kit which produces C and T (control and test) stripes when the solution is applied to the strip. Something similar happens in pregnancy test kits. I understand the purpose of ...
spraff's user avatar
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10 votes
3 answers
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Why do Type II Restriction Endonucleases cleave at palindromic sequences?

Type II Restriction enzymes usually cut only at palindromic sequences. Is there any specific reason for that? Is there any advantage for bacteria if they cleave phage DNA at this type of sequence?
biogirl's user avatar
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How do tea, coffee, and beer dehydrate you?

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 ...
TGar's user avatar
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3 answers
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Are there any multicellular forms of life which exist without consuming other forms of life in some manner?

The title is the question. If additional specificity is needed I will add clarification here. Are there any multicellular forms of life which exist without requiring the consumption (destruction) of ...
CurtisT's user avatar
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7 votes
2 answers
24k 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 ...
James's user avatar
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6 votes
5 answers
2k views

Why do the humans become sleepy after meals?

I don't know about all the mankind, but I know enough people, who becomes sleepy after their meals. Also, I'm not sure, what kind of food do they consume, but I personally get sleepy almost from any ...
abyss.7's user avatar
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Identifying type of inhibitor from $K_m$ and $V_{max}$

Apparently it is possible to identify whether an inhibitor is competitive or non-competitive from graphs of substrate concentration (x axis) and rate of reaction (y axis). There needs to be a line ...
Mirte's user avatar
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Domains in cell membrane

How is movement of proteins and lipids between different domains of cell membrane prevented? Why is the noncytosolic layer not able to do lateral movements between domains but cytosolic layer is able ...
biogirl's user avatar
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4 votes
1 answer
125 views

Apparent paradox in Glucagon action

Glucagon stimulates glycogenolysis and gluconeogenesis, thus increasing the plasma glucose concentration — so that tissues get enough glucose in the fasting state. However glucagon also inhibits ...
ANA negative's user avatar
4 votes
4 answers
12k views

Photosynthesis: What Powers the Splitting of Water?

The splitting of water is an endergonic (non-spontaneous) reaction, and thus would require energy (chemical work to be done) in order to happen. In Photosystem II, an enzyme catalyzes this splitting, ...
LanguagesNamedAfterCofee's user avatar
4 votes
2 answers
1k views

Which hydroxyl from either the phosphate or the glycerol is taken during synthesis of a phospholipid head?

The oxygen anion in the phosphate group is likely to be bonded with a hydrogen cation and thus forming a hydroxyl. When the phosphate group is condensed with glycerol to make a phospholipid, is the ...
hello all's user avatar
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3 votes
2 answers
789 views

What determines whether a reaction using ATP produces ADP or AMP?

Most reactions using ATP seem to involve: ATP → ADP + Pi but in some the reaction is ATP → AMP + PPi followed by hydrolysis of the pyrophosphate: PPi → 2Pi Is there any principle that determines which ...
Ally's user avatar
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3 votes
1 answer
27k views

How is ATP involved in muscle contraction?

The sliding filament mechanism as explained by my text does not elaborate on how ATP is involved in the cross bridge binding and contraction process. How does muscle contraction utilize ATP? In my ...
Fraïssé's user avatar
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50 votes
2 answers
10k views

Why does cutting onions cause tears?​

Why does cutting onions cause tears?​ From a couple of sites, I found that it is because of sulfuric acid produced by onions. But I could not find more details. What is the biochemical pathway by ...
superbug's user avatar
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40 votes
2 answers
12k views

Why do some vegetables taste bitter?

Bitter gourd, cucumber, etc. are bitter to taste. Which chemical causes bitterness in them? I found these when I searched online: this says that it is because of calcium, while this and this talk ...
Mesentery's user avatar
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28 votes
3 answers
179k views

NADH vs. NADPH: Where is each one used and why that instead of the other?

I know NADH is used in cellular respiration and NADPH is used in photosynthesis. What difference does the phosphate group make that the same one isn't or can't be used for both? Is there a greater ...
Gordon Gustafson's user avatar
23 votes
1 answer
792 views

Can a human be made with ovum but without sperm?

This article says that scientists were successful in making a mouse using only a sperm and no egg (ovum). The article also states that this procedure could be applicable to humans. However, I want to ...
Mesentery's user avatar
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20 votes
2 answers
16k 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 ...
Nikolaj-K's user avatar
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18 votes
1 answer
4k views

How do ants follow each other?

I was observing ants in my house.They all were going in a straight line and also some of the ants were coming back through the the same line. I took some water and rubbed the line with my finger, ...
Mesentery's user avatar
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18 votes
4 answers
23k views

Why is the brain dependent on glucose?

The strict dependence of the (human) brain on glucose has always been puzzling to me. While ketones can substitute for a portion of the brain's energy needs, it cannot substitute completely: blood ...
Roland's user avatar
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18 votes
4 answers
9k views

Why don't antiseptic agents kill 100% germs?

I've seen innumerable antiseptic, mouthwash, handwash advertisements that claim to be able to eliminate as much as 99.9% of all germs over a surface...but why not the remaining 0.1% (i.e- why can't ...
paracetamol's user avatar
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15 votes
3 answers
2k views

Is there a fundamental reason that plants cannot fix their own nitrogen?

Plants must have nitrogen to grow. According to the answer to this question, there are no plants that can fix their own nitrogen (without the help of bacteria). Plants get their nitrogen in the form ...
Volker Siegel's user avatar
14 votes
1 answer
11k 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 ...
March Ho's user avatar
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14 votes
4 answers
2k views

During starvation, does the human body do anything to prioritize which organs receive nutrients?

When food is scarce, the body slows its metabolic rate to conserve energy. Are there any other systems or processes that prioritize which organs receive nutrients?
Gabriel Fair's user avatar
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13 votes
4 answers
7k views

Examples of enzymes working in reverse?

I have always been taught that enzymes can catalyze both the forward and reverse reaction, and will increase the reaction rate in both directions. I understand that the thermodynamics of the reaction ...
Arcadium's user avatar
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13 votes
1 answer
2k 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 ...
Matthew Higgins's user avatar

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