Phosphagen Energy System

The phospagen energy system is more than the creatine kinase reaction. Also, let me make it very clear, the CK reaction does not release inorganic phosphate (Pi or PO3-), and is therefore not the cause of skeletal muscle Pi accumulation. The four reactions of this system (when including ATP hydrolysis) are shown in the Figure to the left. I will not summarize these reactions here, for your challenge is to read this material, and then look at this Figure and be able to label the different reactions, the enzymes that catalyze them, and speculate as to the fate of the molecules in the bright yellow color. You will also be able to explain the dynamics of these reactions once the muscle store of CrP becomes low, and relate this to the accumulation of H+, Pi, IMP, and NH4. Finally, you will learn that the CK reaction is an equilibrium reaction, and thereby readily reversible when the biochemical conditions change in muscle in the transition from exercise to rest/recovery.