What is the electron transport chain and what is its function?

The electron transport chain is a series of four protein complexes, along with accessory electron carriers, embedded in the inner mitochondrial membrane of mitochondria. The enzyme ATP synthase is closely associated with the electron transport chain. There are multiple copies of the electron transport chain found in the inner mitochondrial membrane of every mitochondrion. Electrons from electron carriers that have been reduced in either glycolysis, the link reaction or the Krebs Cycle are donated to either Complex I or Complex II.The function of the electron transport chain is to ultimately produce adenosine triphosphate (ATP) which is the source of energy for the majority of cellular processes. The production of ATP is driven by the generation of a H+ ion gradient between the inter-membrane space (between the inner and outer mitochondrial matrix) and the mitochondrial matrix. The H+ gradient is formed as each successive component of the electron transport chain has a greater affinity for electrons. This means energy is released as electrons are travel through the electron transport chain. This energy is then used by the complexes to pump H+ into the inter-membrane space. Subsequently, the H+ ions reenter the matrix through a pore in ATP synthase. The falling of these H+ ions from a high concentration in the inter-membrane space to a low concentration in the mitochondrial matrix leads to a further release of energy. This process is called chemiosmosis. The energy released then leads to a change in structure of ATP synthase and allows it to catalyse the formation of ATP from adenosine diphosphate (ADP) and inorganic phosphate. The metabolic pathway leading to the production of ATP in this manner is called oxidative phosphorylation as electron donors lose electrons (become oxidised) and ADP becomes phosphorylated.