The electron transport system is a coordinated series of reactions that operate in eukaryotic organisms and in prokaryotic microorganisms, which enables electrons to be passed from one protein to another. The purpose of the electron transport system is to pump hydrogen ions to an enzyme that utilizes the energy from the ions to manufacture the molecule known as adenine triphosphate (ATP). ATP is essentially the fuel or energy source for cellular reactions, providing the power to accomplish the many varied reactions necessary for life.

The reactions of the electron transport system can also be termed oxidative phosphorylation.

In microorganisms such as bacteria the machinery of the electron transport complex is housed in the single membrane of Gram-positive bacteria or in the outer membrane of Gram-negative bacteria. The electron transport process is initiated by the active, energy-requiring movement of protons (which are hydrogen ions) from...