Fig. 7. [ADP] calculated from the creatine kinase reaction (equation 2) as a function of phosphocreatine concentration, [PCr], at two pH levels. The solid arrow indicates the effect of a change in [PCr] at pH7.2 on [ADP]. The broken arrow indicates the change in [PCr] needed to maintain [ADP] with a reduction in pH from 7.2 to 6.5.