For smaller animal liver plays a much larger role in all of body Q vs muscle

For smaller animal liver plays a much larger role in

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For smaller animal, liver plays a much larger role in all of body Q vs muscle Labeled AA-isotope studies show the same result - Also points to possible limitations in the use of animal models to study Q 7. SINGLE POOL MODEL for MEASURING Q - Single Pool Model: actual techniques for measuring Q are based on this model o It was previously thought that if you want to measure Q in the body you have to know how much of each of the AAs is in each of the tissues b/c the protein S and C rates are going to be in every tissue § Have to account for all these tissues having Q rates, and the mathematics of this is complex
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SFLORES_2/24/2014 5 But then researchers came up with single pool model which said that you don’t need to calculate rates of Q for individual tissues Can assume body is one big pool of AAs, and the equation used will cancel out any ’s seen from organ to organ - Center of N metabolic pool consists of precursors that could potentially go into syn of proteins o Included in this pool are: FAA’s ; the immediate precursor Urea; which can be hydrolyzed into NH 3 that can be taken up to syn NEAAs Free NH 3 - Where do we get these things that go into the pool? from the breakdown of proteins & oxidation of AAs o 2 sources enrich/ the precursor N pool: 1. N intake: taking in protein, Through digestion and absorption, some AAs, urea and some NH 3 from the gut are flowing in (I) 2. Whole body protein catabolism (C) - How are things removed from the pool? How do you the amount of N in the metabolic pool? (b/c the amounts of FAAs, urea and NH 3 are pretty stable in the body) o Generally the body can’t store FAAs so either you 1. Oxidize the extra AAs which then get excreted in the form of urea (E) or 2. Whole body protein synthesis if needed (S) - Once in the pool, the AAs are now equally mixed with the AAs that come from whole body protein catabolism (see Section IV) 8. ASSUMPTIONS WHEN MEASURING Q USING SPM - To measure Q, use a labeled AA to enrich the N metabolic pool with a tracer AA (small amount of a certain AA) o Assumption 1: When the labeled AA enters the N pool, it mixes completely and indistinguishably amongst the other unlabeled AAs A.k.a- the tracer used ( e.g. - 15 N-Gly) is treated no differently than the regular Gly ( 14 N) and enters in all the metabolic AA reactions of the body
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SFLORES_2/24/2014 6 So whatever AA is selected as the tracer, all other AAs will be treated the same o i.e.- If ½ of the 1% 15 N-Gly is at steady state being removed from the pool, you assume that ½ of 1% of all the other AAs are being removed o This tracer is just representative of all the other AAs in the body that go into making proteins and if not going into proteins then they’re being converted to waste products o Assumption 2: SPM is dependent upon the acceptance that we don’t store N in the body when we take in extra protein from the diet AAs are used to replace the AAs from C of proteins and those AAs that get oxidized will be excreted So AAs from food will mix with all the other AAs into a pool, and a certain proportion is taken out for protein S.
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  • Spring '14
  • Knutson,MitchellD
  • NRG

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