In cellular respiration, which molecule serves as the final electron acceptor in the mitochondria?

In cellular respiration, which molecule serves as the final electron acceptor in the mitochondria?

• A. NADH
• B. Oxygen
• C. Glucose
• D. Carbon dioxide

Answer: (B)

Oxygen serves as the final electron acceptor in the mitochondrial electron transport chain. As electrons flow through the chain, oxygen accepts them and combines with protons to form water. This step is crucial because it regenerates NAD+ and FAD so glycolysis and the TCA cycle can continue, and it sustains the proton gradient that drives ATP synthase to make ATP. The other molecules play different roles: NADH donates electrons and is oxidized back to NAD+; glucose provides the fuel that feeds the whole process; carbon dioxide is a waste product produced by the TCA cycle. If oxygen isn’t available, electrons can’t be accepted at the end of the chain, the chain backs up, and ATP production drops sharply.

Oxygen serves as the final electron acceptor in the mitochondrial electron transport chain. As electrons flow through the chain, oxygen accepts them and combines with protons to form water. This step is crucial because it regenerates NAD+ and FAD so glycolysis and the TCA cycle can continue, and it sustains the proton gradient that drives ATP synthase to make ATP. The other molecules play different roles: NADH donates electrons and is oxidized back to NAD+; glucose provides the fuel that feeds the whole process; carbon dioxide is a waste product produced by the TCA cycle. If oxygen isn’t available, electrons can’t be accepted at the end of the chain, the chain backs up, and ATP production drops sharply.