Describe the synthesis of ATP in oxidative phosphorylation

Oxidative phosphorylation is a critical component of the cell's metabolic pathway, and is responsible for the generation of most of the cell's ATP. Overall, reducing potential in the form of NADH and FADH2, produced by the TCA cycle and beta-oxidation of fatty acid, is oxidised by oxygen to produce water. The energy produced in the reaction pumps protons across the inner mitochondrial membrane, creating potential energy in the form of a proton gradient, which is then used to make ATP from ADP and inorganic phosphate. This process is achieved by a series of transmembrane proteins in the inner mitochondrial membrane, complexes I-IV and ATP synthase. At complex I, the NADH and FADH2 is oxidised, yielding hydrogen and NAD and FAD. The NAD and FAD are recycled back to be reused in the TCA cycle and beta-oxidation, while the hydrogen is split into protons and electrons. Complex I pumps the protons across the membrane, and the electrons are transferred onto ubiquinone, which then transfers them onto complex III. The ubiquinone reduces complex III, which in turn reduces cytochrome c, and pums more protons across the membrane. Cytochrome c then reduces complex IV, which pumps protons across the membrane and uses the electrons along with protons to reduce oxygen to water. The pumping of protons across the membrane generates a proton gradient across the membrane. Protons then diffuse down their concentration gradient through ATP synthase, allowing the potential energy from the proton gradient to be used to synthesise ATP.