ATP generation is associated with the transfer of electrons from NADH and FADH2 to O2 by a series of electron carriers during oxidative phosphorylation.
These oxidation-reduction reactions produce a proton gradient across the inner mitochondrial membrane, which drives the ATP synthase to produce ATP.
The two major subunits of ATP synthase are F0 and F1.
F0 is a transmembrane protein channel that allows protons to pass across the membrane while following an electrochemical gradient.
For each ATP synthesis, 2 H+ travels via F0 (from the intermembrane gap to the matrix).
The majority of ATP generation in eukaryotic cells takes place in the mitochondria during a process known as oxidative phosphorylation.
The reduced electron carriers NADH and FADH2 (obtained from glycolysis, the citric acid cycle, or fatty acid oxidation) send their electrons to oxygen through the electron transport system, which is housed in the inner mitochondrial membrane.
By combining the oxidation of carbohydrates and fatty acids with the production of ATP, food is successfully converted into energy.