Electronic transport chain (ETC), phosphorylation, describes a set of compounds that transfers electrons to electron acceptors from the electron donors through reduction and oxidation reactions. This leads to the coupling of the electron transfer with the transfer of protons (H+) across a membrane. This creates a proton gradient which is electrochemical for synthesis of ATP (Adenosine Triphosphate). Cytochromes are found in the inner membrane and they contain iron. Each of the consecutive cytochromes acts as attraction agents from NAD dehydrogenase until all the cytochromes achieve a high affinity for electrons.

The Chemiosmosis theory describes the movement of ions from a region of high concentration to a region of low concentration. At the initial stages of the electron transport chain, two electrons are transferred into NADH dehydrogenase from NADH. The two electrons are passed to the cytochrome B_C 1 complex by the mobile transfer known as ubiquinone. As electrons are passed from one electron carrier to another, hydrogen ions are transported into the inter-membrane space at three specific points in the chain. The electrons are then transferred separately one at a time into the cytochrome C. The cytochrome oxidase complex enhances the interaction of four electrons with molecular oxygen and 8 hydrogen ions. The four electrons are transported across the membrane while the four electrons, molecular oxygen and four hydrogen ions are used to form water molecules. Each time the electrons move from one carrier to another, they make the hydrogen bonds to break changing the protein shape making it a pump enhancing active transport of 2 H+ from the matrix to the inner membrane space.

The transportation of hydrogen ions creates greater concentration of hydrogen ions in the space between the membranes than in the matrix and this allows for transportation of enzyme ATP synthase. This leads to the combination of two substrates ADP (Adenosine di-phosphate) and phosphate creating energy carrying molecule known as ATP (Adenosine Triphosphate) with the help of enzyme ATP synthase. In the synthesis of ATP, NADH can contribute a maximum of 2.5 ATP whereas FADH2 can produce a maximum of 1.5 ATP. The set of compounds consisting of proteins that are bounded by metal atoms in the space between membranes of mitochondria that transfer electrons to an acceptor from a donor are known as electron transfer chain phosphorylation.