2.11: Hydrolysis of ATP

The molecule adenosine triphosphate (ATP) stores energy for use in cells. It consists of an adenine base, a ribose sugar, and three phosphate groups, with the latter attached to each other through high-energy phosphoanhydride bonds.

These bonds can be broken through the addition of water, releasing one or two phosphate groups in an exergonic process called hydrolysis. This reaction liberates the energy in the bonds for use in the cell. For instance, the sodium-potassium pump utilizes energy from ATP hydrolysis to pump three sodium ions out of the cell and two potassium ions into the cytoplasm. 

When one phosphate group is removed from an ATP molecule, it forms ADP and inorganic phosphate. ADP can be further hydrolyzed to AMP or adenosine monophosphate by the removal of a second phosphate group.