What is the oxidized form of the coenzyme that acts as a hydrogen carrier in cellular respiration?

The oxidized form of the coenzyme that acts as a hydrogen carrier in cellular respiration is indeed NAD+. This coenzyme plays a critical role in metabolic processes, particularly in cellular respiration, where it accepts electrons and hydrogen ions during oxidation-reduction reactions.

In its oxidized state, NAD+ functions as an electron acceptor; it is reduced to NADH when it gains electrons (and a hydrogen ion) during glycolysis and the citric acid cycle. The reduction of NAD+ to NADH is crucial for the process of cellular respiration, as NADH subsequently delivers electrons to the electron transport chain, contributing to ATP production through oxidative phosphorylation.

FAD, while also involved in oxidative reactions and acting as another hydrogen carrier, is specifically known by its reduced form, FADH2. CoA, on the other hand, primarily serves as a carrier for acyl groups in metabolic pathways and does not function directly in electron transport. ATP, while vital for energy transfer within the cell, is not a coenzyme or directly involved in hydrogen carrier activities.

Thus, the role of NAD+ as an oxidized coenzyme highlights its importance in the biochemical pathways that facilitate energy production, making it integral to cellular respiration.