What process uses O2 as the final electron acceptor?

Oxidative phosphorylation is the process that utilizes O2 as the final electron acceptor in cellular respiration. This occurs in the mitochondria, specifically within the electron transport chain (ETC). During oxidative phosphorylation, electrons are transferred through a series of protein complexes and coenzymes in the ETC. As electrons move through these complexes, they release energy, which is used to pump protons across the mitochondrial membrane, creating a proton gradient.

O2 plays a crucial role at the end of this process. After the electrons have moved through the chain, they reach the final protein complex, where O2 combines with the electrons and protons to form water. This reaction is vital because it ensures the continuous flow of electrons through the ETC; without O2 to accept the electrons, the chain would become backed up, halting ATP production.

In comparison, glycolysis occurs in the cytoplasm and can function without oxygen; fermentation is an anaerobic process that also does not utilize O2 and serves in energy production when oxygen is not present; and the citric acid cycle, while it produces electron carriers that feed into oxidative phosphorylation, itself does not directly use O2 as a final electron acceptor. Thus, oxidative phosphorylation is uniquely defined by its dependence on O