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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1answer
300 views

What are the units of enzyme activity?

I was looking at this graph of turnip peroxidase activity and I saw that they use units of 1/sec for enzyme activity. What does this unit intuitively represent and how is it calculated?
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1answer
2k views

Why is GTP gamma S non hydrolyzable?

GTP gamma S is routinely used in studies of G proteins to stably activate the G protein. Comparing the structures of GTP gamma S and GTP, the Sulphur atom replaces the Oxygen attached to the leaving ...
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0answers
65 views

When should endocytosis inhibitors be used in cell binding assays?

I'm beginning to do some cell-binding assays and I would like for my proteins to not be endocytosed by my mammalian cells. Typical suggestions are for the cells to be kept on ice and that the binding ...
5
votes
2answers
662 views

Isotype control antibodies in Flow Cytometry

In a Flow Cytrometry, one can add an Isotype Control Antibody to allow another antibody to bind more specific to the cells. My question is, how can the Isotype Control Antibody add specificity to the ...
7
votes
3answers
225 views

What alternatives are there to the amyloid hypothesis?

Given the recent failure of the Bapi clinical trial, there is a lot of questions that have arised from he amyloid hypothesis. However, I can't really think of many other mechanisms that don't involved ...
8
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2answers
2k views

What is the concentration of ATP in an average cell?

Can someone give me some references showing the average concentration of ATP in a cell?
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2answers
761 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 ...
10
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1answer
337 views

How would I explain different properties of the same protein in different species?

I recently finished an experiment where I analyzed the rate of ATP hydrolysis of Heat shock protein 104 in three species of fungi. They have shown to all have different rates of ATPase activity. How ...
7
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2answers
263 views

How to compute properties of peptides ?

I have been tasked with writing a program for computing properties of a give set of peptides. These peptides are given as 1-letter amino acid sequences and I need to compute the following : Length ...
9
votes
2answers
127 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, ...
5
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2answers
506 views

Why insects are so energy-efficient while flying?

Why are insects so energy-efficient while flying? Is it because of their light weight and aerodynamics or due to very efficient biochemical transformations (food->energy)?
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3answers
9k views

Why can't the brain and red blood cells use fuels other than glucose?

The question is rather straight forward: I have always been curious as to why, but cannot find an explanation online. I can imagine that the mechanism is different for each, but why does brain tissue ...
15
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2answers
3k 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 ...
3
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1answer
146 views

Negative feedback in the fructose metabolism in liver

What happens in liver when large amount of fructose is consumed? I vaguely remember my biochemistry lecturer telling us that the enzymes that process fructose in the liver does not have negative ...
17
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4answers
2k 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?
11
votes
1answer
832 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 ...
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vote
2answers
285 views

How are proteins formed?

Somewhere, I have read that we need to consume proteins to make amino acids to make new proteins. What does it suggest? How do we make proteins from proteins?
3
votes
1answer
1k views

What are the units of Q10 (temperature sensitivity)?

Q10 is the increase in a rate (e.g. activity of an enzyme) observed with a 10 degree temperature increase. According to Wikipedia: It is apparent that the units of R (e.g. mol/g/s) cancel out, ...
3
votes
1answer
303 views

Does caffeine increase the speed at which sperm travels?

I'm not even sure if this claim is true, but... This source states that Caffeine gives both types of sperm a boost, but the Y-sperm would get a little more of a boost. This article reinforces ...
6
votes
1answer
322 views

Are the cytosol and extracellular fluids electrically neutral?

I've found several sources that state that overall, the cytosol of a cell is electrically neutral. The extracellular fluid is also purportedly electrically neutral. How can that be when we have ...
6
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2answers
700 views

What is the correct model for enzyme-substrate complementarity?

This Wikibook shows both proposed models of enzyme-substrate complementarity, the Lock and Key model and the Induced Fit model. I've always been taught that the Induced Fit model is the proper one. ...
3
votes
1answer
297 views

Troubleshooting bioconjugates migration in a SDS-PAGE gel?

We do a lot of bioconjugation chemistry (click chemistry in particular but also NHS and Maleimide chemistries). Our method to valid the conjugation reactions have been to use SDS-PAGE gels followed ...
1
vote
1answer
185 views

Which concentration of BSA is recommended for dynamic light scattering experiments?

What is the recommended concentration of BSA to be mixed with water so as to prepare a very dilute solution in order to clearly study the intensity-intensity correlation with single scattering ? I ...
7
votes
1answer
145 views

What makes a wet dog so stinky?

Similarly, what makes a wet down comforter so stinky? Why do they make no smell except when liquid is added?
4
votes
1answer
464 views

Why are omega-3 fatty acids so easily oxidized when they're incorporated in cellular membranes?

Apparently, this has led to results with clinical significance, as we can see at http://extremelongevity.net/2011/10/03/daily-fish-oil-consumption-may-reduce-lifespan/... The researchers fed a ...
8
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1answer
220 views

How Antioxidants affects Human Metabolism?

I'd like to know how antioxidants affects the human metabolism and which ones are essential for metabolism processes.
1
vote
1answer
126 views

How to manufacture different sized micelles in nano -scale?

I am trying to answer q5: "How can you manufacture micelles in A) nanometerer -scale B) and in ten nanometer -scale?" My Thinking Observations and some thinking Oil in ...
2
votes
1answer
232 views

What happens to colloidal particles in a liquid medium? And how to stabilize it?

Definition Colloid is a dispresion of small particles of one material in another. Definition 2 (Wikipedia) A colloidal system consists of two separate phases: a ...
5
votes
1answer
169 views

Are quaternary protein monomers unique to a particular protein complex?

I know that quaternary protein structures are formed exclusively via non-covalent bonds. My biochemistry professor discussed a viral capsid that is essentially one quaternary structure with 240 ...
6
votes
1answer
181 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 ...
31
votes
4answers
13k 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 ...
7
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1answer
170 views

Protein construct design

I am trying to create some constructs of a certain protein deleting well defined domains (at either terminus) to determine interaction regions with other proteins etc., 3 constructs with varying ...
6
votes
1answer
2k views

Molecularly, why can you straighten or perm hair?

I'm aware that hair can be curly because of the disulfide bond interactions in between cysteine amino acids in alpha-keratin filaments. However, I'm curious as to the biochemistry involved in ...
2
votes
1answer
613 views

What is the reaction mechanism of dopamine hydroxylase converting dopamine to norepinephrine?

The reaction is basically shown below. Dopamine hydroxylase is an enzyme, so I'm not sure if we can have a theory based on organic chemistry. On the other hand, maybe there is a theory that involves ...
10
votes
2answers
481 views

Could hydrogen replace oxygen in cellular respiration?

I was wondering what oxygen actually does in the body. I have seen a few answers to other questions that involve the electron chain and I am really not sure what that is. So I was wondering what ...
11
votes
3answers
1k views

What happens to dextrorotatory amino acids in humans?

As indicated by this question, most of the amino acids in the human body have the L-chirality. As enzymes also have handedness, what happens to the D-amino acids that end up within the human body? Are ...
9
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2answers
24k views

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 ...
9
votes
2answers
4k views

Why is PEG important for efficient yeast transformation?

One way to do an yeast transformation is by using lithium acetate, a single-stranded carrier DNA, and PEG (1). I was wondering why is the polyethylene glycol important for the efficient ...
7
votes
2answers
194 views

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

When food is scarce, the body slows its metabolism. Are there any other systems or processes that encourage prioritization of organs?
8
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2answers
197 views

Solution based measurement of Solvent-Accessible Surface Area of macromolecules

The Solvent-Accessible Surface Area (SASA) is a valuable metric for looking at protein folding and protein-protein interactions. However, this measurement is typically done by calculating the SASA ...
13
votes
1answer
434 views

How fast will cells lyse under hypotonic conditions?

Routinely, lysis of cells with hypotonic solutions is carried out along with some physical (douncing) or enzymatic (lysozyme) method to break open the cells. If one were not to do any of these and ...
11
votes
1answer
90 views

Does a theory exist for the formation of thylakoid structure?

I'm interested in how the structure of the thylakoid forms into its characteristic highly rugose stacks of grana. What causes the thylakoid to invaginate and self-associate, albeit with what appear to ...
7
votes
1answer
189 views

When collecting cell lysates for a Western blot, how do I induce di-sulfide bonds?

I would like to conduct a simple dimerization experiment for some protein I'm collecting from a cultured cells. My thought is, that if I'm running a non-reducing, denaturing PAGE gel, then removing ...
9
votes
3answers
184 views

Does GFAJ-1 use Adenosine triarsenate as its energy currency?

Regarding the bacteria found in Mono Lake, CA that scientists believe uses or can use arsenic in its DNA backbone where life as we know it uses phosphorus (according to their experiments depriving the ...
6
votes
2answers
576 views

For how long and how cold should I perform ethanol/isopropanol precipitations of RNA or DNA?

Precipitating nucleic acids using either isopropanol or ethanol is a very common operation, and I've read some very different protocols on the duration and temperature the precipitation should be ...
10
votes
3answers
692 views

Why do people say that trans fatty acids are bad for your health?

I've heard from several sources that trans FAs are bad for you and their consumption will lead to cardiac problems, and that they are indigestible. But I also learned from biochemistry that they are ...
6
votes
2answers
803 views

Basic Amino Acid Residue Binding Mechanism to DNA

I understand that many protein DNA binding domains bind to DNA via basic residues such as Arginine and Lysine. But what is the mechanism used to bind to DNA and where on the DNA would these residues ...
2
votes
1answer
91 views

Structure of RAP Antibodies (Specifically RAP-5)

[EDIT] - Have just found not one but two papers that address my structure problem. However they concern RAP-1A, so I guess my question is now what is the difference in structure and function of ...
7
votes
1answer
2k 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?
6
votes
1answer
164 views

Is there an enzyme for the transformation of the hydroxyl group?

I would like to know, is there any enzyme which does the transformation of hydroxyl group to any other functional group using the enzyme. The substrate is aromatic hydroxyl group. Product should not ...