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BabcockHall

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Posts posted by BabcockHall

  1. Amino acids are synthesized from their own pathways, entirely separate from the synthesis of RNA.  A family of twenty aminoacyl tRNA synthetase enzymes is responsible for joining the amino acid to its cognate tRNA.  These are questions and topics that it takes a biochemistry textbook chapters to develop.  

  2. Apologies, I misread your question, and I was pointing the way toward answering a different question.  Aspartate is also used as a donor in the biosynthetic pathway that produces inosine monophosphate (check the two steps in the synthesis of AICAR) and in the urea cycle.  I disagree that a side chain is necessarily more reactive and can think of some examples to illustrate this.  However,  I am not sure what makes one nitrogen donor used in one reaction and a different nitrogen donor used in another.

  3. I would not assume any particular value for Vmax.  Instead I would rearrange the Michaelis-Menten equation into the form v/Vmax = (S)/{KM + (S)}.  This means that the velocity one calculates will be relative to Vmax.  I decided to avoid using concentration brackets in this comment, because I think that they might be causing the unwanted strikethroughs.

  4. I am familiar with some kinds of protein chromatography, but I now have to run a nickel column for the first time.  The protein of interest bears a histidine tag, and uur protein is believed to be a dimer or possibly a tetramer of identical subunits.  As is typical the nickel column is the first step after sonication of E. coli cells.  How do I choose the best volume of gel to use?  If I use too little, there will be loss of the protein in the load and wash.  If I use too much, the protein is more dilute, and in some sense I am wasting gel.

     

    At first glance I can see that one issue is the need to estimate what fraction of soluble cell protein is the protein of interest.  I might be tempted to estimate this as being no more than 20% of the soluble protein.  A second issue is capacity of the gel, and based on my general knowledge of protein IEX chromatography it occurs to me that there might be some variation from one protein to another, based upon accessibility of the his tag.

  5. I assume that you are referring to Serum glutamic pyruvic transaminase, also known as alanine aminotransferase.  We cannot provide medical advice on this forum; that is best done by consulting your physician.  You may find this link helpful in terms of background reading.

    https://www.summitmedicalgroup.com/library/adult_health/tst_sgpt_tst/

  6. On 4/9/2020 at 11:50 PM, Rembrandt said:

    I thought pyruvate was also needed in the citric acid cycle? so why then making lactate out of it in the first place?

    Lactate is already made by anearobic glycolysis in the cells (converting glucose to lactate), right? so why make even more?

    It makes sense to me that you would want to make pyruvate out of lactate, since this could be a waste product of the anaerobic respiration, but why the other way around.

    Muscle cells undergoing anaerobic consumption of glycogen produce more pyruvate than they can consume aerobically via the TCA cycle.  The pyruvate is instead converted into pyruvate.  Your second sentence implies that there is an additional way to make lactate, but there isn't.

  7. Are enzymes equally active at all pH values, or do they have an optimum pH?  Does the balanced reaction produce/consume protons?  The mechanism that you drew implies the answer.  In other words if one used unbuffered water, would the pH of the water gradually change with time.

     

    With respect to why convert pyruvate into lactate, there are several ways to think about it.  If a muscle cell did not, what would happen to the ratio of NAD to NADH within that cell? 

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