Structure of the mitochondrial respirasome (electron transport complexes)

The membranes of bacterial cells and mitochondria contain a series of complexes that catalyze the oxidation of NADH. A lengthy electron transport chain leads eventually to the reduction of oxygen to water. Electrons lose energy as they pass down the chain and this is coupled to the transport of protons (H⁺) from one side of the membrane to the other. This proton gradient is used to drive ATP synthesis by the ATP synthase complex. The mechanism of making ATP is chemiosmosis but the pathway is often called oxidative phosphorylation or respiration.

The discovery of chemiosmosis (Chemiosmotic Theory) is one the few examples of a genuine paradigm shift. It is largely due to the work of Peter Mitchell [Ode to Peter Mitchell].