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.
Answer by Nicole Cooper. Confidence votes 32. The role ATP plays in muscle contraction is that ATP binds to sites on myosin heads, inducing a conformational change in the actin binding site and reducing the affinity for the actin substrate. Hydrolysis of ATP then cocks the myosin head and moves it closer to the z disk.