Question

Energy conservation in thioesters, acetyl-CoA and succinyl-CoA:

A. ensure irreversibility of the citrate synthase reaction, in the case of acetyl-CoA
B. ensure the production of GTP in the case of succinyl-CoA
C. in the case of acetyl-CoA is required because OAA concentration in the cell are very low due to the endergonic nature of the malate dehydrogenase reaction
D. occurs through large enzyme complexes
E. All of the above responses are correct and therefore E is my best choice.

Answer 1

Answer:

B. ensure the production of GTP in the case of succinyl-CoA

Explanation:

Succinyl CoA like acetyl-CoA has a thioester bond with very negative free energy of hydrolysis. In this reaction, hydrolysis of the thioester bond leads to the formation of phosphoester bond with inorganic phosphate. This phosphate is transferred to histidine residue of the enzyme and this high energy unstable phosphate is finall transferred to GDP resulting in generation of GTP.

Hence the answer is B. ensure the production of GTP in the case of succinyl-CoA.