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 Muscular system is the organ system whose primary function is movement and flexibility. The muscular system is made up of the muscles that let you move. There are three kinds of muscle in your body. Smooth muscle moves food through the digestive system.Cardiac muscle pumps blood throughout the body.he Muscular system is the organ system whose primary function is movement and flexibility. The muscular system is made up of the muscles that let you move. There are three kinds of muscle in your body. Smooth muscle moves food through the digestive system.