Which molecule is the final electron acceptor in aerobic respiration?

Which molecule is the final electron acceptor in aerobic respiration?

• A. NAD+
• B. Water
• C. Oxygen
• D. Carbon dioxide

Answer: (C)

In aerobic respiration, the electrons carried by NADH and FADH2 flow through the electron transport chain and are ultimately transferred to molecular oxygen. Oxygen is the final electron acceptor because it has high electronegativity and readily accepts electrons and accompanying protons to form water. This final transfer is what drives the proton gradient across the inner mitochondrial membrane, powering ATP synthase to produce ATP. If oxygen isn’t available, the chain can’t accept electrons, NADH and FADH2 can’t be reoxidized to NAD+ and FAD, and ATP production via oxidative phosphorylation drops sharply. NAD+ is an electron carrier that gets reduced to NADH earlier in metabolism and then needs to be reoxidized to continue, so it isn’t the terminal sink. Water is produced at the end when oxygen accepts electrons and protons, not the recipient itself. Carbon dioxide is a waste product released from metabolism and is not used to accept electrons.

In aerobic respiration, the electrons carried by NADH and FADH2 flow through the electron transport chain and are ultimately transferred to molecular oxygen. Oxygen is the final electron acceptor because it has high electronegativity and readily accepts electrons and accompanying protons to form water. This final transfer is what drives the proton gradient across the inner mitochondrial membrane, powering ATP synthase to produce ATP. If oxygen isn’t available, the chain can’t accept electrons, NADH and FADH2 can’t be reoxidized to NAD+ and FAD, and ATP production via oxidative phosphorylation drops sharply.

NAD+ is an electron carrier that gets reduced to NADH earlier in metabolism and then needs to be reoxidized to continue, so it isn’t the terminal sink. Water is produced at the end when oxygen accepts electrons and protons, not the recipient itself. Carbon dioxide is a waste product released from metabolism and is not used to accept electrons.