What is the net gain of NADH from one turn of the Citric Acid Cycle?

In one complete turn of the Citric Acid Cycle (also known as the Krebs cycle or TCA cycle), the net gain of NADH is indeed three molecules. This is because during the cycle, three specific steps involve the reduction of NAD+ to NADH.

1. First, during the conversion of isocitrate to alpha-ketoglutarate, isocitrate is oxidized, and NAD+ is reduced to NADH while carbon dioxide is released.

2. Next, while converting alpha-ketoglutarate to succinyl-CoA, another round of oxidation occurs where NAD+ is again reduced to NADH, along with the release of another carbon dioxide molecule.

3. Finally, when succinate is oxidized to fumarate, a third NAD+ is reduced to NADH.

Each of these steps contributes one NADH, leading to a total of three molecules of NADH generated for each turn of the cycle. The production of NADH is crucial as it plays a key role in energy production later during oxidative phosphorylation, indicating the cycle's importance in cellular respiration.