Introduction Mitochondria produce significant adenosine triphosphate (ATP) via oxidative phosphorylation the electron transport chain (ETC) is found in the inner mitochondrial membrane and receives electrons from the reduced coenzymes NADH this is the reduced form of NAD+ NAD+ → NADH + H by dehydrogenases FADH2 this is the reduced form of FAD+ NAD+ and FAD+ receives electrons from the catabolism of energy-rich molecules (e.g., glucose) the reduced coenzymes donate their electrons to the ETC approximately 3 ATP molecules for each NADH approximately 2 ATP molecules for each FADH2 NADPH produced by the hexose monophosphate (HMP) shunt involved in a number of processes such as the production of glutathione biosynthesis/anabolic reactions respiratory bursts cytochrome P450 systems