The molecule adenosine triphosphate (ATP) is made up of two parts - adenosine.... and triphosphate. The triphosphate is made up of three phosphoryl groups. ATP is often referred to as an energy store or energy currency of the cell.

The two bonds between between the phosphoryl groups are high energy bonds as the electrons in the bonds are in a high energy state.

ATP can turn into adenosine diphosphate (ADP) by a chemical reaction. ADP has one less phosphoryl group than ATP.

The chemical reaction is an hydrolysis reaction, as water is used.

ATP + H2O -> ADP + HPO4 + H+ + energy

Energy is released as the electrons move to a lower energy state.

ATP is used for moving ions across membranes, biosynthesis, and muscle contraction.

ATP hydrolysis can be coupled with reactions requiring energy.

ATP at Khan Academy.

ATP hydrolysis reaction at Khan Academy.