If a pair of electrons is passed along the entire length of the electron transport chain, ATP is made in 3 separate places. This is the only point at which oxygen is required by aerobic organisms. The more steps required, the more energy released. The mechanism of electron transport and oxidative phosphorylation is basically the same in anaerobes as in aerobes with minor variations. One of the most frequently used inorganic electron acceptors is nitrate, whereas fumarate is a more common organic electron acceptor.
Less energy is realized during electron transport under anaerobic conditions.
The difference in the oxidation-reduction potential between the donor and acceptor is not sufficient to generate more than one or two ATP molecules. Fermentation, as indicated earlier, is a metabolic process that releases energy from a sugar or other organic molecule.