In oxidative phosphorylation, what is the primary role of NADH and FADH2?

• A. They act as membrane channels that allow $H_{+}$ to diffuse back into the matrix to generate ATP without a proton gradient.
• B. They donate high-energy electrons to the electron transport chain, which helps drive proton pumping and ATP synthesis.
• C. They transport oxygen to complex IV to serve as the terminal electron acceptor in the electron transport chain.
• D. They directly catalyze the phosphorylation of ADP to ATP at ATP synthase by providing the active site for the reaction.

Answer: (B)