An electron acceptor is a chemical entity that can accept electrons from another chemical entity. By accepting the electrons, the acceptor is reduced, and thus prior to receiving the electrons the entity is called "an oxidized electron acceptor" and after receiving them it is called "a reduced electron acceptor".
Many electron acceptors are able to transfer the electrons to other acceptors, becoming oxidized in the process. Thus the distinction between an electron acceptor and an electron donor is often not determined by the actual chemical entity, but by the role it plays in a particular reaction. However, some acceptors in biological reactions only accept electrons and do not transfer them further. Those are often known as "terminal electron acceptors".
Examples of electron acceptors used in biology include inorganic small molecules (e.g. oxygen, nitrate, iron (III), manganese (IV), sulfate), organic molecules (e.g. NAD+, FAD, quinones) and proteins (e.g. ferredoxins, flavodoxins, cytochromes, blue copper proteins). They differ in the number of electrons that they transfer and in their electron affinity.
Child Classes: α-NAD(P)+ (0) , α-NAD(P)H (0) , an unknown oxidized electron acceptor (0) , an unknown reduced electron acceptor (0) , Membrane-Electron-Carriers (14) , NAD(P)+ (2) , NAD(P)H (2) , NADHX (2)
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