When ATP (adenosine triphosphate) is converted to ADP (adenosine diphosphate), a phosphate group is removed from ATP through a process called hydrolysis, which involves the addition of water. This reaction breaks the bond between the second and third phosphate groups of ATP, resulting in the formation of ADP, an inorganic phosphate (Pi), and the release of energy
. The energy released during this hydrolysis is used by cells to power various biological functions such as muscle contraction, active transport across membranes, biosynthesis of macromolecules, and other cellular activities
. The reaction is energetically favorable and releases about 7.3 kcal/mol (or approximately 30.5 kJ/mol) of free energy, which cells harness to perform work
. After ATP is converted to ADP, the ADP can be recycled back into ATP through cellular processes like oxidative phosphorylation in mitochondria, substrate- level phosphorylation during glycolysis and the citric acid cycle, or via the creatine phosphate system in muscles. This regeneration requires energy input, often derived from the breakdown of nutrients, allowing the ATP-ADP cycle to continuously supply energy to the cell
. In summary:
- ATP hydrolysis to ADP releases energy by breaking a high-energy phosphate bond.
- This energy fuels cellular processes such as muscle movement, chemical reactions, and active transport.
- ADP and inorganic phosphate are produced and can be recycled to regenerate ATP.
- The cycle of ATP hydrolysis and regeneration is fundamental to cellular energy metabolism
