What are the functions of the electron transport system?
The mitochondiral electron transport chain consists of a series of metalloproteins bound to the inner membrane of the mitochondria. The metal centres and other cofactors in these proteins act, in essence, as a molecular wire, carrying electrons from the strongly reducing products of the citric acid cycle (NADH, succinate) to highly oxidizing dioxygen. The direct oxidation of these substrates by O2 would release a great deal of energy as useless heat. Instead, indirect oxidation occurs, whereby the electrons are passed through a series of metal clusters and cofactors, including flavins, iron-sulphur clusters, cytochromes, and copper centres. These groups are embedded in large membrane-bound proteins, and the passage of electrons through them is coupled to the transport of protons across the membrane, from the interior matrix space of the mitochondria to the intermembrane space. In effect, the energy released by the electron flow is used to do work, work that creates a proton concentrati
