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.
In skeletal muscle, the contraction allows the bone to move, thereby allowing your body to move. In the heart, the cardiac muscle pumps the blood into the arteries. The smooth muscles in blood vessels are used to pump blood in one direction (in veins, which is in low pressure, there are valves which prevents backflow).