Definition of ADP

Adenosine diphosphate (ADP) is a nucleotide composed of adenine, ribose sugar, and two phosphate groups. It plays a crucial role in cellular energy transfer, acting as a key component in the ATP (adenosine triphosphate) cycle. When ATP is hydrolyzed to release energy, it converts to ADP and inorganic phosphate, which can then be recycled back into ATP through cellular respiration. ADP also participates in signaling pathways and metabolic processes within the cell.