Adenosine Triphosphate (ATP)

**Information:** Adenosine triphosphate is a nucleotide composed of a nitrogenous purine base (adenine), a D-ribose sugar, and three phosphates (phosphoric acid residues). When ATP contains only one phosphate group, it is referred to as adenosine monophosphate (AMP). with two phosphate groups, it is known as adenosine diphosphate (ADP). **General meaning:** ATP is a macroergic compound whose hydrolysis releases a large amount of energy resulting from the electrostatic repulsions between negatively charged oxygen atoms. The hydrolysis of ATP produces phosphate and ADP, along with the release of energy according to the reaction: ATP + H₂O → ADP + P. Under specific conditions, ATP can also hydrolyze to produce AMP and bisphosphate: ATP + 2H₂O → AMP + P-P. The energy released from this process can then be used to drive endergonic reactions. **Functions in photosynthesis:** During the initial phase of photosynthesis, ATP is synthesized, driven by a transmembrane proton gradient: ADP + P → ATP + H₂O. In the subsequent phase, ATP hydrolysis occurs: ATP + H₂O → ADP + P. The energy released from this reaction is used in biosynthetic reactions, such as the Calvin Cycle.