A series of membrane-linked oxidation-reduction reactions in which electrons are transferred from an initial electron donor through a series of intermediates to a final electron acceptor (usually oxygen). The electron transport systems of respiration and photosynthesis are the major chemical energy sources in aerobic organisms.
A number of other electron transport systems are known besides those of respiration and photosynthesis. Heterotrophic bacteria have a *respiratory chain
similar to that in eukaryotes and a microsomal electron transport system is responsible for desaturation of fatty acids. See also photosystems I and II