An electron transport chain (ETC) consists of a number of complexes. These series of complexes transmit electrons from electron donors to electron acceptors by way of redox reactions where in reduction and oxidation takes place simultaneously. This transmission of electron is coupled with the transmission of protons across a membrane. Electron transport chain is basically a process employed to extract energy from sunlight in photosynthesis. It is also used in case of oxidation of sugars in cellular respiration.