The extracellular concentration of protons is much higher than intracellular its level. Responsi- ble for generation and maintaining this difference is the proton pump (H+) present in the outer cell membrane. A proton pump uses ATP as a substrate and expels H+ from the cell; consequently, the ions are asymmetrically located and the electrochemical gradient appears, which is used in many physiological processes such as cellular growth, osmoregulation and transport of substances into the cell.