Adenosine triphosphate is composed of three phosphate groups, the nitrogenous base adenine, and the five-carbon sugar ribose. These phosphate groups are connected to each other by two high-energy bonds known as phosphoanhydride bonds. By undergoing hydrolysis, where a phosphate group is removed by breaking a phosphoanhydride bond, ATP is converted into adenosine diphosphate (ADP) and energy is released. This energy can be utilized by the cell for its functions.
When the cell has excess energy, acquired from the breakdown of consumed food or through photosynthesis in plants, it stores this energy by attaching a free phosphate molecule to ADP, transforming it back into ATP.
The energy in ATP is stored in the covalent bonds between phosphates, with the bond between the second and third phosphate groups containing the highest amount of energy (approximately 7 kcal/mole). This specific covalent bond is known as a pyrophosphate bond.
The energy released from the hydrolysis of ATP into ADP is employed to carry out various cellular tasks, often by coupling the energy-releasing ATP hydrolysis with energy-consuming reactions.
Sodium-potassium pumps utilize the energy obtained from ATP hydrolysis to transport sodium and potassium ions across the cell membrane. Furthermore, phosphorylation facilitates the energy-requiring reaction.
ATP for biological energy storage
