How many NADH are produced in one complete cycle of the Citric Acid Cycle?

In one complete cycle of the Citric Acid Cycle (also known as the Krebs cycle or TCA cycle), a total of three NADH molecules are produced. This happens during various steps of the cycle where NAD+ is reduced to NADH.

Specifically, the cycle begins with the conversion of acetyl-CoA to citrate, and through several reactions, there are three key steps where NAD+ is reduced to NADH:

1. Isocitrate is oxidized to α-ketoglutarate, producing one molecule of NADH.

2. α-Ketoglutarate is then converted to succinyl-CoA, yielding a second NADH molecule.

3. Finally, malate is oxidized to oxaloacetate, generating the third NADH.

Consequently, for every turn of the cycle, three NADH molecules are harvested, playing a crucial role in cellular respiration as they are used in the electron transport chain to generate ATP through oxidative phosphorylation. Thus, the total of three NADH molecules produced confirms the correct answer is indeed three.