(BIOCHEMISTRY QUESTION) Consider the following reactions, which are two consecut
ID: 992129 • Letter: #
Question
(BIOCHEMISTRY QUESTION) Consider the following reactions, which are two consecutive steps in the TCA cycle. The two reactions are catalyzed by two independent enzymes, malate + NAD + oxaloacetate + NADH G10= +29.7 kJ/mol acetyl-CoA + oxaloacetate citrate + CoA G10= -31.5 kJ/mol. How can the first reaction in the list proceed in the direction of products in this pathway with such a high positive free energy change?
a. this reaction is coupled to ATP hydrolysis
b. the second reaction isn the list uses the oxaloacetate keeping its concentration low resulting in a G that is about zero for the first reaction.
c. the answer to this question cannot be determined from the information given
Explanation / Answer
The best answer is; c. the Q for the first reaction in the list is much larger than its Keq and as such is irreversible, because the citrate synthesis from acetyl-CoA and oxaloacetate to make citrate and has a large - delta G of -31.5 KJ/ mol.
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