CHEM 153A Study Guide - Final Guide: Oxaloacetic Acid, Succinic Acid, Pyruvic Acid

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scarletporpoise754

14 Jun 2016

School

UCLA

Department

Chemistry and Biochemistry

Course

CHEM 153A

Professor

Tienson

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Document Summary

50% labeled on the bottom, 50% labeled on the top (either or) (1/2 of the population) Carbons from acetyl-coa end up in oxaloacetate (as those. Middle 2 cs of oxaloacetate still be in the compound till in the end of the 2nd. In the 2nd round of tca cycle, additional acetyl-coa will not get labeled in c round. All labeling was eliminated in co2 in the 2nd round of tca cycle. On c2 and on c3 (the 2 middle cs on succinate) After 1st round, either on carbonyl c or on methyl carbon (c3) After 2nd round, carboxylic acid ends up as co2 while c3 is still in. Oxaloacetate! (only lose unlabeled c from acetyl-coa) randomization = labeled c ends up in any carbon in succinate! (all 4) All labeling is still present, but is equally distributed across. All c"s (50% -> 25% on each c) Lose 1 carboxylic acid to co2, another 25% to co2.

Related Questions

1. If the keto carbon atom (#2) of pyruvate were to be labeled with ¹⁴C , which of the carbon atom(s) of oxaloacetate would be labeled at the end of one turn of the citric acid cycle? (numbering similar to sugars with #1 the carboxylic acid carbon, #2 the keto group, #3 the methyl group) [Ogstonâs symmetry argument was that citric acid exhibited chirality when it bound to enzyme explaining why neither carbon of acetylCoA came off as CO₂ in the first turn of the cycleâthe same chirality argument does not hold for succinate because it is symmetrical about a bond]

a) None. The label will be lost in CO₂.

b) #1 carbon

c) #2 carbon

d) #3 carbon

e) #4 carbon

f) the #2 and #3 carbons will be labeled

g) the #1 and #4 carbons will be labeled

2. If acetyl-CoA is labeled at the methyl carbon (#2) with ¹⁴C, how many turns of the citric acid cycle (starting at the formation of Citrate) will be required to first release some labeled CO₂ ?

a) less than one complete turn

b) one complete turn (back to citrate)

c) more than one, but less than two complete turns

d) only after two complete turns

3. How many ATP or equivalents would be generated from the Succinyl-CoA step after the equivalent of all its four carbons (donât worry about position) were converted to CO₂? State your assumptions, e.g. ample AcCoA is present.

CHEM 153A Study Guide - Final Guide: Oxaloacetic Acid, Succinic Acid, Pyruvic Acid

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