A terminal electron acceptor refers to a molecule, ion, or compound involved in cellular respiration and anaerobic metabolism that accepts electrons at the end of the electron transport chain. It plays a crucial role in the final step of oxidative phosphorylation, during which it receives low-energy electrons and undergoes reduction.
In aerobic respiration, oxygen functions as the terminal electron acceptor, obligatorily receiving electrons to form water. Conversely, in anaerobic respiration, various other compounds may serve as terminal electron acceptors depending on the organism. Examples include nitrate, nitrite, sulfate, fumarate, or even certain metals like iron or manganese.
The terminal electron acceptor acts as the final electron sink, receiving the high-energy electrons derived from the oxidation of reduced electron carriers, such as NADH or FADH2, during earlier steps of the electron transport chain. This electron flow generates a proton gradient across the inner mitochondrial or bacterial membrane, contributing to the synthesis of ATP by the ATP synthase complex.
The selection of the terminal electron acceptor depends on several factors, including cellular environment, the type of metabolism, and the availability of specific acceptor molecules. The choice of acceptor significantly influences the ability of an organism to produce energy efficiently under different conditions. Additionally, the transfer of electrons to these acceptors enables the regeneration of oxidized electron carriers, allowing subsequent cycles of cellular respiration to occur.
