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 a smoker's finger or mustache get yellowish by nicotine?

Tobacco use is the leading cause of preventable death around the world.$\ce{^1}$ The stain is considered as a "tell-tale" sign for identifying smokers. Multiple materials stated that it's due to ...
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150 views

Is honey in hot green tea unsafe?

I used Google to try to figure out what kind of mixture honey has with hot water, and I found several Ayurvedic sources claiming that honey in hot water is toxic. For example: Honey – NEVER Put It ...
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564 views

True or false & fill in the blanks

A ribosome is where amino acids are linked together by peptide bonds. A virus is NOT considered prokaryotic because it does not have a membrane. The nucleotide ATP is one of the most used energy ...
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peptide MHC microarray

"The recent technology is peptide–MHC microarray or artificial antigen-presenting chip. In this technique, recombinant peptide–MHC complexes and co-stimulatory molecules are immobilized on a ...
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903 views

Why does NAD+ become reduced if it gains a hydrogen proton?

I've heard that $NAD^+$ gains a Hydrogen proton during glycolysis and the Krebs cycle and becomes reduced to $NADH$. However, isn't reduction when a molecule receives an electron? Maybe I've been ...
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What are the functions of disulphide bonds?

What are the functions of disulphide bonds between amino acids in proteins or peptides?
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185 views

Molecules and human memory

Has it been demonstrated that the memory of human brain is just connections between neurons, not "long" molecules such as RNA or proteins?
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How to manage fat-gluten oxidation in celiac disease?

Assume you have been in non-gluten diet 20 years. You built mass 8 mass with substances containing gluten (endogenous gluten stored in fat). Then, celiac disease is diagnosed. You have been 3 ...
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498 views

Can a dNTP be built into a RNA strand?

DNA consists of deoxyribonucleotides, RNA consists of ribonucleotides. They differ mainly (apart from the uracil / thymine difference) in the sugar part, the deoxyribose and the ribose. Those two ...
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64 views

Do different emotions produce different tears?

Do tears of joy, laugh, grieve, and others contain different things or are they all the same?
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71 views

Are alpha-ketoglutarate and glutamate involved in all transamination reactions?

Is it true that for all biochemical transamination reactions, that alpha-ketoglutarate and glutamate serve as the amino group acceptor and donor, respectively? If this is true, then is it safe to ...
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118 views

Are all dipeptides synthesizable?

Probably a basic question, but are all possible dipeptides synthesizable? For 20 amino acids, there should be in principle 190 dipeptides; do they all exist or is there chemistry that makes some ...
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161 views

Why do many DNA solutions contain additional compounds?

DNA solubility data in only water is scarce. A previous question asked for a quantification of DNA solubility in water. It seemed like it would be easily answerable, however isn't quite that simple ...
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Increasing/decreasing signal intensity in Western blotting

So I was in class and my professor was explaining western blotting. It seems as though there's more than one way to increase or decrease the signal intensity. He presented us the challenge to discover ...
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124 views

Why is coconut oil healthier when it has so much saturated fat?

I noticed that coconut oil has ~96% saturated fat, and I was under the assumption that saturated fats = bad for health. Why is it that coconut oil is healthier to alternatives with much less ...
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183 views

Substitute 25mM dNTPs mix with 10mM dNTPs

I need to make a solution of multiple compounds, one of them is dNTPs. The recipe calls for 20 μl 25 mM dNTPs in a 1250 μL master mix. Unfortunately I do not have it available at that concentration, ...
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145 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 ...
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Melting point of a fatty acid?

What factors determine the melting point of a fatty acid? Chain length The number of methylene group The ionized state of the fatty acid Its degree of saponification Its ability to alter the ...
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94 views

Is DNA mutation locally energetically stabilizing the DNA molecule

I am no biologist, but as a physicist, a spontaneous mutation (seen as a chemical transformation) should lower the energy of the system, at least locally. So I wonder if any research has been done ...
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656 views

Difference between protein channels, protein carriers and protein pumps?

I'm revising for my biology exam and I don't fully comprehend the difference between protein channels, carriers and pumps. I know that: Protein channels do not require ATP (passive transport) The ...
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532 views

Does pH affect Michaelis constant?

I have been trying to confirm the Km of a substrate (which is 34 +/- 4 mM). This value was obtained in 50 mM MOPS, pH 6.3. I conducted my kinetics assay in a buffer of pH 7 and obtained a Km value in ...
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971 views

Why are nitrogenous bases of DNA hydrophobic if they can hydrogen bond?

Why are nitrogenous bases of DNA hydrophobic if they can hydrogen bond? Is it that they are only relatively hydrophobic? This forum explains it but does not give an example of the structure.
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37 views

Why is there a compound highlighted in red in a KEGG Module search?

Considering the following module: http://www.kegg.jp/kegg-bin/show_module?M00115+C00003 why is the compound C00003 marked in red?
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740 views

Green Film Build up in Glass Water Bottle

So I have this Large Water Jug that I fill only water with. And this is the 2nd time there has been a layer of green film that builds up at the bottom of the bottle. I don't have any way of getting ...
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60 views

How are ketone bodies used?

While searching for literature on ketone bodies, I can only seem to find how they are synthesized, but not how they are broken down. I'm looking for the series of events with enzyme names and ...
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529 views

What is the result of meiosis?

Is the result of meiosis ONLY the sex gametes (male and female) which later meet to form a somatic cell? Sometimes I feel as if my book is hinting towards meiosis is the process where sperm cells meet ...
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Question about flavodiiron protein

I came across an article about flavodiiron proteins that are responsible for reducing ${\rm O}_2$ to ${\rm H}_2{\rm O}$ thereby protecting the anaerobic prokaryotes and some eukaryotes from oxidative ...
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68 views

Why do oncogenes show genetic dominance?

As we know that tumor suppressor gene causes cancer only when both the alleles are recessive in nature.But in case of oncogenes if only one allele is dominant it can cause cancer.Why in case of ...
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132 views

Formation of peptide bond..?

Proteins peptide bond is made by condensation process in which a molecule of water is released and according to this process it is not favorable in water systems than how peptide bond is formed by ...
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654 views

Anaerobic respiration choice in E. coli

Under anaerobic conditions E. coli has two options to generate ATP: fermentation (substrate-level phosphorylation), and respiration (proton gradient, chemisomotic phosphorylation). Which is favored? ...
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108 views

Trimming of tRNA precursors

From Molecular Biology of the Cell (4th edition) by Bruce Alberts et al. (Chp 6, Pg 338) : Both bacterial and eucaryotic tRNAs are typically synthesized as larger precursor tRNAs, and these are ...
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What is optical density in Lowry's protein estimation method?

I have a few questions: What is an OD value? Why do we use blank solution in Lowry's protein estimation method? If The OD of a protein is 0.01, what does it mean? Thanks in advance.
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Structure of biological membranes?

Integral membrane proteins have functional asymmetry i.e. they have two different domains of proteins performing different functions. these proteins have Tyr and Trp amino acid residues at the ...
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65 views

How is it decided that one drug is better than others by X times?

I read in Tortora and Derrickson that : Enkephelins are 200 times powerful than morphine in their analgesic effects. I wonder how exactly researchers arrive at a number (like 200 here). I also ...
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613 views

What exothermic reaction distinguishes warm blooded animals?

I would appreciate an answer specifically in the form of an exothermic chemical reaction. Namely, the one primarily responsible for generating heat in warm blooded animals that does not take place in ...
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272 views

What chemicals can be detected from one's sweat?

This question came to mind after reading this article. The article speaks of inducing sweating to determine by a roundabout fashion the amount of salt therein. I'm no medic but I find myself wondering ...
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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 ...
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105 views

How to build a trimeric protein structure from monomeric PDB file?

Problem: I have a PDB file, with a monomer, but I would like to show the entire structure - which is trimeric - but I don't understand how to merge/build or combine the monomeric units to its full ...
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1answer
149 views

What is a mechanical cue?

I was attending a talk related to neurogenesis. So one professor was asking a question related to biochemical cues and mechanical cues (related to signaling pathways I believe). Cue as far as I ...
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54 views

dAT joining: please define

I came across a reference to dAT joining in my reading of Genentech by Sally Hughes. The technique is described in passing as a technique for joining DNA fragments used around the late sixties to ...
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Is there a short-term, very strong anesthetic, which can be blocked/delayed by other substances?

Question migrated from World Building SE. (For fictional use only, of course :) ) I am looking for an anasthetic which fulfills the following criteria: very strong effect, induces a comatose state ...
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1answer
85 views

How to calculate the Jaccard index [closed]

I want to calculate the Jaccard index between two compounds. What is the algorithm? I have searched for it, it just gives the formula but how to apply it on compounds is not known to me. Can you help? ...
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Does mung bean nuclease cleave a phosphate group when it's chewing off 5' or 3' ssDNA ends?

I'm looking to create blunt ends from sticky ends with mung bean nuclease for subsequent ligation. Does anyone know full mechanism by which mung bean nuclease will do this? In particular after the ...
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1answer
109 views

Edman method to identify peptides with Phenylisothiocyanate (PTH)

We all know that in this method the PTH reacts with the first amino acid (aa) from the N-terminal to the peptide and separates from it giving PTH-aa so that we can know the amino acids sequence in the ...
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1answer
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Making the sense of enzyme Km comparisons

I have encountered comparisons of the Michaelis-menton constant (Km) a few times. Generally speaking if Km of an enzyme is higher, then it's affinity to its substrate is lower. How does this make ...
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747 views

Why would an Eadie-Hofstee Plot be non-linear? [closed]

Besides cooperativity between multiple active sites on an enzyme, what are the other reasons for the Eadie-Hofstee plot to be non-linear?
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Help me understand my membrane potential assignment

Epithelial with the ability to transport NaCl is bathed in an isotonic salt solution with these values (in mM): 136 Na, 6 K, 140 Cl. The intracellular concentrations are: 45 Na, 100 K, 13 Cl. The ...
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1answer
801 views

What are the ways to test for protein in the canine urine?

I know that one way is to use the reagent sticks and the refractometer, but this is inaccurate. Is protein distinguishable when using a microscope? Is it time sensitive(i.e. have to test it right ...
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1answer
28 views

epitope prediction/ mapping

B-CELL EPITOPE PREDICTION Regarding this article: "Such a molecule can be synthesized or, in case of a protein, its gene can be cloned into an expression vector."----- is a particular line in ...
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Bohr effect in respiration

Would I be correct in saying that the Bohr effect is ONLY related to the concentration of [H+] in the tissues. Obviously the concentration of carbon-dioxide can contribute to this concentration by ...