Which of the following coenzymes are required for the oxidation of pyruvate to acetyl-CoA by the pyruvate dehydrogenase complex?

• A. FADH\(_2\), ATP, Ubiquinone, Vitamin B\(_{12}\)
• B. NAD\(^+\), Biotin, Coenzyme Q, Tetrahydrofolate
• C. NADP\(^+\), Biotin, Coenzyme Q, Pyridoxal phosphate (PLP)
• D. NAD\(^+\), Coenzyme A, Thiamine pyrophosphate (TPP), Lipoic acid, FAD

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the role of the pyruvate dehydrogenase complex (PDC). It is a multi-enzyme complex responsible for converting pyruvate into acetyl-CoA, a key intermediate in cellular respiration. This process involves oxidative decarboxylation and requires several coenzymes.
2. Step 2: Identify the coenzymes involved in the reaction. The pyruvate dehydrogenase complex uses five essential coenzymes: NAD\(^+\) (nicotinamide adenine dinucleotide), Coenzyme A (CoA), Thiamine pyrophosphate (TPP), Lipoic acid, and FAD (flavin adenine dinucleotide). Each plays a specific role in the reaction mechanism.
3. Step 3: Exclude the incorrect options. For example, FADH\(_2\) is the reduced form of FAD and is not directly required in this reaction. ATP, Ubiquinone, Vitamin B\(_{12}\), Biotin, Coenzyme Q, Tetrahydrofolate, NADP\(^+\), and Pyridoxal phosphate (PLP) are not involved in the pyruvate dehydrogenase complex reaction.
4. Step 4: Match the correct coenzymes to their functions: (a) TPP is involved in the decarboxylation of pyruvate, (b) Lipoic acid acts as a carrier for acyl groups, (c) Coenzyme A accepts the acetyl group to form acetyl-CoA, (d) FAD and NAD\(^+\) are involved in electron transfer during the oxidation process.
5. Step 5: Summarize the correct answer. The coenzymes required for the oxidation of pyruvate to acetyl-CoA by the pyruvate dehydrogenase complex are NAD\(^+\), Coenzyme A, Thiamine pyrophosphate (TPP), Lipoic acid, and FAD.