(3) ADP+Pi+H+ATP+H2O Al the steady-state, the average intracellular [ATP] is between 35mM. If the [ATP] drops below this narrow range, the cell will die within minutes due to cellular energy depletion, a condition known as bicenergetic catastrophe'. In order to prevent sudden and rapid declines in cellular [ATP], hurnan skeletal muscle utilizes the phosphocreatine system to 'buffer' cellular ATP concentration ([ATP]). The phosphocreatine system relies upon the power of the hydrolysis of creatine-phosphate to provide the energy needed to phosphorylate ADP to ATP. Under the chemical standard state (G), the hydrolysis of phosphocreatine liberates 42.8kJmot1 : G=42.8kJmot1