For the pyruvate dehydrogenase complex, what is the specific chemical function o
ID: 837715 • Letter: F
Question
For the pyruvate dehydrogenase complex, what is the specific chemical function of the lipoic acid cofactor?
A. activation of acetyl-CoA
B. oxidation of lipoic acid
C. reduction of NAD+
D. transfer of the acetyl group to CoA
E. decarboxylation of pyruvate
for the pyruvate dehydrogenase complex as well, what is the specific chemical function of the FAD cofactor?
A. activation of acetyl coa
B. oxidation of lipoic acid
c. reduction of NAD+
d transfer of the acetyl group to CoA
e. decarboxylation of pyruvate
Explanation / Answer
1) D. transfer of the acetyl group to CoA
E2: Dihydrolipoyl transacetylase which uses lipoamide and coenzyme A as its prosthetic groups
E2 (dihydrolipoyl transacetylase with cofactor lipoamide) oxidizes hydroxyethyl- to acetyl- and then transfers acetyl- to CoA, forming acetyl-CoA.
2) B. oxidation of lipoic acid
E3: Dihydrolipoyl dehydrogenase which uses flavin adenine dinucleotide (FAD) and nicotinamide adenine dinucleotide (NAD+) as its cofactors.
E3 oxidizes the thiol groups of the dihydrolipoamide back to lipoamide.
First, FAD oxidizes dihydrolipoate back to its lipoate resting state, producing FADH2. Then, a NAD+ cofactor oxidizes FADH2 back to its FAD resting state, producing NADH.