ADP

ADP, or adenosine diphosphate, is a molecule that is essential in the metabolism of cellular energy. When ATP (adenosine triphosphate) is hydrolyzed, or broken down, one of its three phosphate groups is released, resulting in ADP. The hydrolysis of ATP to ADP is an exergonic reaction that produces energy that cells use to power a variety of biological processes such as muscle contraction, nerve impulse transmission, and protein synthesis. ADP can be hydrolyzed further to AMP (adenosine monophosphate), releasing another phosphate group and more energy. ADP can be converted back into ATP via a process known as oxidative phosphorylation, which occurs in cells’ mitochondria. Energy released from the breakdown of glucose and other molecules is used to pump hydrogen ions (protons) across the inner mitochondrial membrane, creating an electrochemical gradient. This gradient is then used to drive the synthesis of ATP from ADP and inorganic phosphate by ATP synthase, a complex enzyme. ADP is also involved in cellular processes other than energy metabolisms, such as protein synthesis regulation, cell signaling, and membrane trafficking. ADP-ribosylation, for example, is a process in which ADP is transferred to specific amino acid residues on proteins, thereby regulating their function and activity.