Adenosine triphosphate (ATP) is the energy currency of the cell. It is the most important energy carrier which carries energy in the two terminal phosphate bonds (called as high energy bonds or energy rich bonds). Equal amounts of usable energy are released per mole of ATP or ADP hydrolysis : ATP+H2O⇌ADP+Pi+7.3Kcalmol−1 ADP+H2O⇌AMP+Pi+7.3Kcalmol−1