What role do electron carriers like NAD+ and FAD perform in respiration?

Electron carriers such as NAD+ and FAD play a crucial role in cellular respiration by transporting and transferring electrons through various metabolic pathways, particularly in the process of oxidative phosphorylation. During cellular respiration, glucose is broken down, and high-energy electrons are released. These electrons are then transferred to NAD+ and FAD, converting them into their reduced forms, NADH and FADH2, respectively.

Once reduced, NADH and FADH2 carry the electrons to the electron transport chain located in the inner mitochondrial membrane. Here, the electrons move through a series of protein complexes, creating a proton gradient across the membrane. The energy released in this process is used to synthesize ATP from ADP and inorganic phosphate via the enzyme ATP synthase.

Thus, these electron carriers are essential for the conversion of the energy stored in nutrients into a usable form, ATP, which powers various cellular functions. Their primary role in respiration is fundamentally tied to their ability to facilitate the transport and transfer of electrons, making option B the most accurate choice.