Final answer:
When ATP is broken down into ADP and inorganic phosphate, energy is released. Conversely, when ADP and inorganic phosphate are joined to form ATP, energy is stored. The breaking of the phosphodiester or phosphoanhydride bonds within ATP releases the energy needed for cellular reactions and processes.
Step-by-step explanation:
ATP molecules consist of an adenine, a ribose, and three phosphate groups. The chemical bond between the second and third phosphate groups, termed a high-energy bond, represents the greatest source of energy in a cell. When ATP is broken down into ADP and inorganic phosphate, energy is released. Conversely, when ADP and inorganic phosphate are joined to form ATP, energy is stored. The breaking of the phosphodiester or phosphoanhydride bonds within ATP releases the energy needed for cellular reactions and processes.