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.
The source of energy that is used to power the movement of contraction in working muscles is adenosine triphosphate (ATP) â the bodyâs biochemical way to store and transport energy. However, ATP is not stored to a great extent in cells. So once muscle contraction starts, the making of more ATP must start quickly.