Respiration In Plants — BIOLOGY STD 11 Science — Question

Oxidative phosphorylation is the synthesis of energy rich ATP molecules with the help of energy liberated during oxidation of reduced co-enzymes (NADH, FADH₂) produced in respiration. The enzyme required for this synthesis is called ATP syntheses. It is considered to be the fifth complex of electron transport chain. ATP syntheses are located in FT or head piece of F₀ -F₁ or elementary particles. The particles are present in the inner mitochondrial membrane. ATP syntheses becomes active in ATP formation only where there is a proton gradient having higher concentration of H⁺ or protons on the F₀ side as compared to F x side (chemiosmotic hypothesis of Peter Mitchell).
Increased proton concentration is produced in the outer chamber or outer surface of inner mitochondrial membrane by the pushing of proton with the help of energy liberated by passage of electrons from one carrier to another. Transport of the electrons from NADH over ETC helps in pushing three pairs of protons to the outer chamber while two pairs of protons are sent outwardly during electron flow from FADH_2. The flow of protons through the F₀ channel induces F₁ particle to function as ATP-synthase. The energy of the proton gradient is used in attaching a phosphate radical to ADP by high energy bond. This produces ATP. Oxidation of one molecule of NADH₂ produces 3 ATP molecules while a similar oxidation of FADH₂ forms 2 ATP molecules.