Question

One acetyl coA molecule entering the TCA cycle gives rise to molecules of NADH.

• A. two
• B. three
• C. four
• D. five

Answer 1

The correct option is B three

There are 3 points during the Kreb's cycle, when NAD is reduced to NADH.
1. Oxidative deecarboxylation of isocitrate to $\alpha$-ketoglutaric acid, catalysed by isocitrate dehydrogenase.
2. Oxidative decarboxylation of $\alpha$-ketoglutaric acid to succinyl Co-A, catalysed by $\alpha$-ketoglutarate dehydrogenase.
3. Dehydrogenation of malate to oxaloacetate, catalysed by the enzyme malate dehydrogenase.