adenosine triphosphate (ATP)
creatine phosphate (CP)
ATP supplies the energy for muscle contraction to take place. In addition to its direct role in the cross-bridge cycle, ATP also provides the energy for the active-transport Na+/K+ and Ca2+ pumps. Muscle contraction does not occur without sufficient amounts of ATP. Phosphocreatine, also known as creatine phosphate (CP) or PCr (Pcr), is a phosphorylated creatine molecule that serves as a rapidly mobilizable reserve of high-energy phosphates in skeletal muscle and the brain to recycle adenosine tri phosphate; which is the energy currency of the cell.