The definition of ATP in biology ATP or adenosine triphosphate is the energy-carrying molecule essential for all living organisms. It is used to transfer the chemical energy necessary for cellular processes. Adenosine triphosphate (ATP) is an organic compound that provides energy for many processes in living cells.

Often the feeling passes, and you bounce back to your regular robust self. But if you struggle with a constant lack of energy, you may have a problem deep within your cells. Mitochondria are the power source inside all your body's cells. These tiny structures fuel the body by producing molecules called adenosine triphosphate or ATP.