During the citric acid cycle, which molecule is primarily responsible for transporting electrons?

The correct answer highlights the role of NAD+ as a key electron carrier in the citric acid cycle. Throughout this metabolic pathway, NAD+ acts as an oxidizing agent, meaning it accepts electrons during various reactions. When NAD+ picks up electrons, it is reduced to NADH, which then carries these high-energy electrons to the electron transport chain. There, NADH plays a crucial role in oxidative phosphorylation, ultimately contributing to ATP production.

In contrast, while FADH2 also serves as an electron carrier in the cycle, it is usually generated from specific reactions involving succinate and is not primarily responsible for electron transport overall in the cycle. ATP, although vital for energy transfer within the cell, does not function in electron transport. Citrate, on the other hand, is an important intermediate of the cycle but does not participate in electron transfer. Understanding these roles clarifies why NAD+ is recognized as the primary electron transporting molecule within the citric acid cycle.