What is the final electron acceptor in the electron transport chain?

The final electron acceptor in the electron transport chain is oxygen. During cellular respiration, particularly in the oxidative phosphorylation stage, electrons are transferred through a series of protein complexes in the inner mitochondrial membrane. As electrons move through these complexes, they lose energy, which is used to pump protons (H+ ions) into the intermembrane space, creating a proton gradient.

At the end of this chain, the electrons are transferred to molecular oxygen, which combines with these electrons along with protons to form water. This reaction is crucial because it drives the entire process of the electron transport chain and allows for the continuation of ATP production. If oxygen were not present to accept the electrons, the electron transport chain would back up, leading to a halt in ATP production and ultimately affecting cellular energy levels.

The other options do not serve as final electron acceptors in this context: NAD+ is involved earlier in the process by accepting electrons during glycolysis and the Krebs cycle, water is a product of the reaction rather than an acceptor, and carbon dioxide is produced during the Krebs cycle, rather than participating in the electron transport chain. Thus, the role of oxygen as the final electron acceptor is essential for efficient energy production in aerobic respiration.