Adenosine triphosphate (ATP) is an energy-carrying molecule that fuels cellular functions. It is often referred to as the "energy currency" of the cell, as it provides readily releasable energy in the bond between the second and third phosphate groups. ATP is used for a variety of processes in the body, including:

• Muscle contraction: ATP is required for muscle fibers to contract and generate force.

• Nerve impulse propagation: ATP is involved in the transmission of nerve impulses throughout the body.

• Substrate phosphorylation: ATP is used to add phosphate groups to other molecules, which can activate or deactivate them.

• Ion transport: ATP is involved in the movement of ions across cell membranes, which is important for maintaining proper cellular function.

• DNA/RNA synthesis: The breakdown of ATP through hydrolysis serves a broad range of cell functions, including signaling and DNA/RNA synthesis.

ATP is synthesized in several ways, including cellular respiration, beta-oxidation, and ketosis. It is also formed from the process of photosynthesis in plants and cyanobacteria. Although cells continuously break down ATP to obtain energy, ATP is also constantly being synthesized from ADP and phosphate through the processes of cellular respiration. Most of the ATP in cells is produced by the enzyme ATP synthase, which converts ADP and phosphate to ATP.