Which molecule acts as the final electron acceptor in the electron transport chain?

In the electron transport chain, the final electron acceptor is oxygen. The primary role of oxygen in this context is to receive electrons that have been passed along the chain, culminating in a series of redox reactions that ultimately produce ATP. As the electrons travel through various protein complexes in the inner mitochondrial membrane, they facilitate the pumping of protons across the membrane, creating a proton gradient. This gradient subsequently powers ATP synthase to generate ATP.

Once the electrons reach the end of the chain, they need to be accepted by a terminal electron acceptor to prevent a backlog of electrons that would halt cellular respiration. Oxygen's high electronegativity makes it an excellent choice for this role, as it readily combines with the electrons and protons (hydrogen ions) to form water. This process is essential for the longevity of aerobic respiration, as it allows for the continued flow of electrons through the chain and the production of energy.

In contrast, carbon dioxide does not participate in the electron transport chain; rather, it is a byproduct of cellular respiration, specifically in the Krebs cycle. NADH and FADH2, while essential for donating electrons to the chain, are not the final acceptors. They participate earlier by donating their electrons to the chain