Work Step by Step
The making of ATP from ADP and phosphate is a process that requires energy, which means it is an endergonic, not exergonic, process. ATP stores energy in its three-phosphate tail; when one of the phosphates is cleaved off the molecule, energy is produced that can be used to drive cellular processes. In the hydrolysis of ATP, water is used to break off one of the phosphate groups, which yields energy and ADP. In the phosphorylation of ATP, a phosphate group is transferred to another molecule.