What is the primary role of NAD+ in cellular respiration?

NAD+ plays a crucial role in cellular respiration as an electron carrier. During the metabolic processes of glycolysis and the citric acid cycle, glucose is metabolized, and electrons are extracted. NAD+ accepts these electrons, becoming reduced to NADH. This conversion is essential because NADH then carries the electrons to the electron transport chain, where they are used to generate ATP, the energy currency of the cell. This function is fundamental to energy production in aerobic respiration, highlighting NAD+'s importance in facilitating the flow of electrons through metabolic pathways.

The other options do not adequately represent the primary functions of NAD+. While energy storage is a significant aspect of cellular metabolism, it is not NAD+'s role; instead, that function is primarily associated with molecules such as ATP and glycogen. Although glucose uptake is vital for cellular energy, it involves different transport mechanisms and proteins rather than being directly facilitated by NAD+. Lastly, synthesizing proteins is a key process in cellular function but does not involve NAD+ directly; instead, it relates more to amino acids and ribosomes. Therefore, NAD+'s main role as an electron carrier is pivotal for effective energy production.