<P> Oxidative phosphorylation (or OXPHOS in short) (UK / ɒkˈsɪd. ə. tɪv /, US / ˈɑːk. sɪˌdeɪ. tɪv /) is the metabolic pathway in which cells use enzymes to oxidize nutrients, thereby releasing energy which is used to produce adenosine triphosphate (ATP). In most eukaryotes, this takes place inside mitochondria . Almost all aerobic organisms carry out oxidative phosphorylation . This pathway is probably so pervasive because it is a highly efficient way of releasing energy, compared to alternative fermentation processes such as anaerobic glycolysis . </P> <P> During oxidative phosphorylation, electrons are transferred from electron donors to electron acceptors such as oxygen, in redox reactions . These redox reactions release energy, which is used to form ATP . In eukaryotes, these redox reactions are carried out by a series of protein complexes within the inner membrane of the cell's mitochondria, whereas, in prokaryotes, these proteins are located in the cells' intermembrane space . These linked sets of proteins are called electron transport chains . In eukaryotes, five main protein complexes are involved, whereas in prokaryotes many different enzymes are present, using a variety of electron donors and acceptors . </P> <P> The energy released by electrons flowing through this electron transport chain is used to transport protons across the inner mitochondrial membrane, in a process called electron transport . This generates potential energy in the form of a pH gradient and an electrical potential across this membrane . This store of energy is tapped when protons flow back across the membrane and down the potential energy gradient, through a large enzyme called ATP synthase; this process is known as chemiosmosis . The ATP synthase uses the energy to transform adenosine diphosphate (ADP) into adenosine triphosphate, in a phosphorylation reaction . The reaction is driven by the proton flow, which forces the rotation of a part of the enzyme; the ATP synthase is a rotary mechanical motor . </P>

Is the electron transport chain part of oxidative phosphorylation