Abstract
This chapter describes structures and functions of the mitochondrial oxidative phosphorylation system (OXPHOS). The principal function of mitochondria is to provide the cell with adenosine triphosphate (ATP). Mitochondria produce ATP by a process called “oxidative phosphorylation.” In this process, the reduced forms of nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FADH2) formed during fatty-acid oxidation, glycolysis, and in the citric-acid cycle, are oxidized to NAD+ and FAD, while the free energy of these reactions is indirectly used for the phosphorylation of adenosine diphosphate (ADP) to ATP. The rate of mitochondrial respiration (oxygen consumption) and ATP synthesis depends on intramitochondrial ADP concentration. As the adenine nucleotide translocator links the processes of ATP production with those of ATP use, the carrier plays a key role in oxidative phosphorylation and is a potential regulatory site of this biochemical pathway. The adenine nucleotide translocator has multiple isoforms in mammals that may adjust the kinetic properties of the enzyme to the specific metabolic needs of various tissues.