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Feb
5
comment About photosynthesis VS respiration
In addition, electrons passed down the electron transport chain (respiratory redox chain) during respiration are (usually) accepted by oxygen forming water. In PS, water is 'split' and it is the electrons formally 'held' in an O-H bond that are used to reduce NADP(+) to NADPH. The 'splitting' of water, of course produces oxygen (see the hill reaction): the oxygen evolved in PS comes from water not CO(2)
Dec
31
comment What's the point of glycolysis in fermentation?
In alcohol fermentation, the alcohol dehydrogenase reaction plays a similar role to LDH in lactate fermentation, and there is also no net oxidation or reduction.
Dec
31
comment What's the point of glycolysis in fermentation?
@Chinmay Kanchi. Can you give an example of one fermentative system where NADH 'contributes to ATP gain' (and how?).
Dec
31
comment What's the point of glycolysis in fermentation?
But where does the 2 NADH come in? In lactate fermentation, for example, the (one) NADH produced in the GAPdh reaction is reoxidized in the LDH reaction. Glycolysis may be thought of as the splitting of glucose without any net oxidation or reduction, and where the 'purpose' of the LDH reaction is to regenerate the NAD+ (from NADH) to allow the GAPdh reaction to proceed.
Aug
12
answered How much penicillinase is needed to deactivate 125mg of amoxicillin?
Aug
11
comment Correct enzyme nomenclature
The fundamental problem here is that enzymes are classified by the reaction they catalyze, not by gene or protein entity. Two enzymes that catalyze the same reaction that are not related from an evolutionary point of view are given the same EC number. Have a look at the mess of EC 1.1.1.1 (alcohol dehydrogenase)
Aug
11
comment Is our genome decaying (see “Genetic Entropy”), and, if so, is this evidence for our genome being “young”?
This is a link to the PNAS paper quoted. See also here. It is surely a gross aberration to conclude that the genome is not old because the genome is 'decaying', where all evidence point to the contrary. I note with interest the following statement on one of the links from John Salfords blog "In the beginning God created the heavens and the Earth" (Genesis 1:1). This result was not published by the PNAS until very recently, it would seem.
Aug
7
comment Multiple transcripts encoding for one protein
Yes there are, and a great example is microtubule-associated protein tau, the key protein component of the paired helical filament of Alzheimer's disease. In this case differential mRNA splicing gives rise to four different protein forms (isoforms) of bovine tau and six different isoforms of human tau, differing in relative molecular mass. The isoforms may be easily distinguished on an SDS-gel.
Aug
6
comment Why is leucine amino acid used the most in proteins and tryptophan the least?
One somewhat controversial theory, which I cannot find a reference to, is that the codon for tryptophan is a relatively late addition to the genetic code. There are quite a few proteins without any tryptophan. Mitochondrial malate dehydrogenase is, I think, an example. [ Edit. See here and here for discussion of the late arrival of the trp codon].
Aug
6
revised Is NADPH salt still usable after an hour at room temperature?
added qualification to sentence
Aug
6
revised Is NADPH salt still usable after an hour at room temperature?
Added EC number link
Aug
6
revised Is NADPH salt still usable after an hour at room temperature?
qualified a sentence
Aug
6
revised Is NADPH salt still usable after an hour at room temperature?
Major formatting revision, and added some extra material on purification
Jul
31
comment Is NADPH salt still usable after an hour at room temperature?
The question I posed is what is the difference between hydrated and unhydrated NADPH other than water of hydration. I am aware of the distinction that your chemist friend makes. You say NADPH is unstable in water. What is the breakdown product? Does it cause bleaching of the A340? The only reaction of NADH with water that I know of is the enzymic hydration of the 5,6-double bond.
Jul
31
comment Doing a medical study on yourself?
A very famous experiment (Shemin and Rittenberg) to calculate the half-life of the red blood cell (120 days, or thereabouts) involved Shemin ingesting 66g of [15N]glycine. See here. (A note for molecular biologists: N-15 is NOT radioactive]
Jul
31
comment Doing a medical study on yourself?
@ user137 Was it Linus Pauling? :-)
Jul
31
revised Is NADPH salt still usable after an hour at room temperature?
added 2 characters in body
Jul
31
revised Is NADPH salt still usable after an hour at room temperature?
added 48 characters in body
Jul
31
comment Are trees the only source of large amounts of oxygen?
(+1) And, of course, the oxygen comes from the splitting of water.
Jul
31
comment Are trees the only source of large amounts of oxygen?
One of the great discoveries of biology is that the oxygen evolved in photosynthesis comes from water not CO2. How do trees release 'the O from the CO2 into the atmosphere'??