What is the main function of NAD+ in cellular respiration?

NAD+ plays a crucial role in cellular respiration by serving as an electron carrier. In the process of glycolysis and later in the citric acid cycle, NAD+ accepts electrons during the oxidation of substrates, transforming into its reduced form, NADH. This conversion is pivotal because NADH then carries the high-energy electrons to the electron transport chain, where they are used to generate ATP through oxidative phosphorylation. The ability of NAD+ to shuttle electrons contributes to the cell's energy production efficiency. Hence, its main function as an electron carrier is fundamental to both energy metabolism and overall cellular respiration.