Adenosine 5'-diphosphate (ADP) plays a critical role in cellular energy transfer. It is primarily involved in the conversion of energy within cells through processes like cellular respiration and photosynthesis. When ATP (adenosine triphosphate) is hydrolyzed to release energy, it forms ADP, which can then be rephosphorylated back to ATP during processes such as oxidative phosphorylation in mitochondria. This cycle is essential for powering various cellular activities, including muscle contraction, nerve impulse propagation, and biochemical synthesis.

In research, ADP is used to study enzyme kinetics, particularly those of kinases and ATPases, which are crucial for understanding metabolic pathways and cellular signaling. It also serves as a substrate in assays to measure the activity of enzymes involved in energy metabolism. Additionally, ADP is utilized in the development of therapeutic agents targeting blood clotting, as it plays a role in platelet activation and aggregation. Its applications extend to biotechnology, where it is used in the production of energy-regenerating systems for synthetic biology and metabolic engineering.