Oxidative phosphorylation is the synthesis of energy-rich ATP molecules with the help of energy liberated during oxidation of reduced coenzymes ( NADH and FADH2 ) produced in respiration. TH enzyme required for the synthesis is called ATP synthase. It is the fifth complex of ETS. During this process, a number of oxidation-reduction reactions occur and lead to the generation of a proton gradient. The enzyme ATP synthase (complex V) consists of and components. The Fl headpiece is a peripheral membrane protein complex and contains the site for ATP synthesis from ADP and inorganic phosphate whereas component is a part of the membrane protein complex, which acts as a channel for the crossing of the protons from the inner mitochondrial membrane to the mitochondrial matrix. For every two protons passing through complex, synthesis of one ATP molecule takes place.