How Phosphocreatine Buffers Cyclic Changes in ATP Demand in Working Muscle

What is the role of phosphocreatine in energy metabolism of muscle tissue? The various roles that have been proposed over the last 50 years all fall into two categories: spatial transport and storage of high-energy phosphate. We analyse the function of phosphocreatine as a temporal buffer within a muscle cell on the basis of a simple model. Our model is based on the assumption of equilibrium of the creatine kinase reaction $$Mg.ADP + PCr + {H^ + }Mg.ATP + Cr.$$ Also, all species are allowed to diffuse freely between mitochondria and myofibrils. In the absence of any anatomical evidence and following the reasoning of Meyer et al.(1984), we do not incorporate compartmentation of ATP and ADP in mitochondrial or myofibrillar pools.