Electron transfer chain

The electron transfer chain, also called the electron transport chain, is a sequence of complexes found in the mitochondrial membrane that accept electrons from electron donors such as NADH[?] or succinate, shuttle these electrons across the mitochondrial membrane creating an electrical and chemical gradient, and through the proton driven chemistry of the ATP synthase (aka the F₀F₁ particle), generate adenosine triphosphate.

There are five complexes normally associated with the electron transfer chain.

• Complex I - NADH dehydrogenase, also called NADH Coenzyme Q reductase.
• Complex II - Succinate - Coenzyme Q reductase[?].
• Complex III - Coenzyme Q - cytochrome c reductase.
• Complex IV - Cytochrome c oxidase.
• Complex V - ATP Synthase, also known as the F₀F₁ particle.

All of these are proteolipid complexes, with the first four containing either flavins, iron-sulfur clusters, copper centers, or heme moieties. Complexes I, III, and IV are proton pumps. Complex II is part of the Krebs cycle and does not pump protons, and Complex V uses the electrochemical potential generated to create ATP. Complex IV is the terminus of the electron transfer chain, consuming oxygen and making water.

• Cytochrome c

Cytochrome c is also an essential part of the electron transfer chain. It is a soluble protein loosely associated with the inner mitochondrial membrane, and transfers electrons between Complexes III and IV.

See also:

• cytochrome
• mitochondrion
• chloroplast