1 Chemically, ATP is an adenine nucleotide bound to three phosphates. 2  There is a lot of energy stored in the bond between the second and third phosphate groups that can be used to fuel chemical reactions. 3  When a cell needs energy, it breaks this bond to form adenosine diphosphate (ADP) and a free phosphate molecule.
calf muscle pump. calf muscle pump. an action of the calf (soleus) muscles in which the muscles contract and squeeze the popliteal and tibial veins, forcing the blood in those veins to move upward toward the heart. Also called soleus pump.
Every muscle cell has some amount of ATP. Adenosine triphosphate (ATP) is the way your body uses biochemicals to store and use energy. There is enough ATP in the cell that the muscle can use immediately, but only enough to last for about three seconds. The muscle must replenish the ATP levels quickly, using a high-energy phosphate compound called creatine phosphate.