The oxidative decarboxylation of pyruvate to Acetyl-CoA (the link reaction) requires the Pyruvate Dehydrogenase Complex and which set of five cofactors?
Answer and explanation
Correct answer: D. Thiamine pyrophosphate (TPP), Lipoamide, Coenzyme A, FAD, and NAD+
- TPP (derived from vitamin , for decarboxylation by ),
- Lipoamide (for acyl transfer by ),
- Coenzyme A (pantothenic acid derivative, to accept acetyl group),
- FAD (riboflavin derivative, for electron transfer in ),
- (niacin derivative, the final electron acceptor).
- Lipoamide (for acyl transfer by ),
- Coenzyme A (pantothenic acid derivative, to accept acetyl group),
- FAD (riboflavin derivative, for electron transfer in ),
- (niacin derivative, the final electron acceptor).
- Step 1: The link reaction connects glycolysis to the Krebs cycle in the mitochondrial matrix: .
- Step 2: The pyruvate dehydrogenase multi-enzyme complex () uses five distinct cofactors:
Answer
Thiamine pyrophosphate (TPP), Lipoamide, Coenzyme A, FAD, and NAD+
Why not the others: 'Biotin, Pyridoxal phosphate...' are cofactors for carboxylation (pyruvate carboxylase) and transamination reactions, respectively; 'Tetrahydrofolate...' functions in one-carbon metabolism; 'Ascorbic acid, Glutathione...' are antioxidants, not catalytic cofactors for PDH.
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