What is the terminal electron acceptor in an electron transport chain?

In the context of cellular respiration, the terminal electron acceptor in an electron transport chain is essential for the process of oxidative phosphorylation, which is a critical step in energy production within cells. Oxygen serves as the final electron acceptor after a series of electron transfers through various protein complexes in the mitochondrial inner membrane.

During this process, electrons derived from metabolic substrates, primarily during glycolysis and the Krebs cycle, are transferred to carriers such as NADH and FADH2. These carriers then donate electrons to the electron transport chain. The transfer of electrons down the chain ultimately culminates in their acceptance by oxygen, which combines with protons (H+) to form water. This reaction is vital as it helps to maintain the flow of electrons through the chain, driving the proton motive force necessary for ATP synthesis.

The role of oxygen is particularly important because, without it, the electron transport chain would become backed up with electrons, inhibiting ATP production and leading to the cessation of cellular respiration. Anaerobic organisms utilize different terminal electron acceptors, but in aerobic respiration, oxygen is indispensable.

Other candidates mentioned, like glucose, NAD+, and FAD, play different roles in metabolism. Glucose is the primary substrate that provides the electrons for the pathway,