ATP is a storage molecule that provides the energy for many life functions. The formation ADP from ATP releases energy while new energy from food intake rebuilds ATP molecules for future use.
Adenosine triphosphate, or ATP, is a molecule comprising a carbon and nitrogen ring, a sugar group and a group of three phosphates. The triphosphate group is the active part of the molecule and responsible for most of the energy release. The cytoplasm of all cells contains ATP. Adenosine triphosphate is useful in energy transfer because the negative charges of the triphosphate region create a degree of instability and reactivity in the molecule; ATP readily reacts to lose phosphate groups and reduce its negative charge.
Through a hydrolysis reaction a water molecule reacts with ATP, causing it to lose a phosphate group. The result of ATP hydrolysis is the molecule ADP and energy. The mitochondria of animal cells easily converts ADP back to ATP using energy from food. In plants, ATP reforms via the energy from sunlight.
ATP plays a major role in many functions within cells, including the building of cytoskeletal elements and the synthesis of DNA and RNA. ATP also shortens muscle filaments, leading to muscle contraction. In this role, ATP is essential in movement, respiration and heart function.