Oxidation/Reduction

Oxidation/reduction reactions involve the transfer of electrons from a molecule being oxidized (the electron donor) to a molecule being reduced (the electron acceptor). Because one or more electrons are transferred, neither oxidation nor reduction can occur without the other occurring simultaneously. An example of an oxidation/reduction reaction is the following reaction, catalyzed by succinate dehydrogenase, from the citric acid cycle:

> Succinate + FAD <=> Fumarate + FADH 2

Succinate is the electron donor (so it is oxidized) and FAD is the electron acceptor (so it is reduced). The products of the reaction are fumarate (oxidized) and FADH 2 (reduced). Cells typically use a common set of electron acceptors, such as FAD, NAD+ and NADP+. Many of these molecules deposit their electrons into the electron transport system.

See also: Electron Transport (from Chapter 15), NADP+, NAD+, FAD