Answer
The phophagen system comprises two methods in which a phosphate ion (Pi) is transferred from an ADP molecule to another ADP to form an ATP, or a phosphate is transferred from creatine phosphate to an ADP to form an ATP. This is a fast system through which the muscle derives immediate energy after it has used up the limited amount of oxygen supplied for aerobic oxidation by myoglobin.
Work Step by Step
In the first method, a phosphate ion (Pi) is transferred from an ADP molecule to another ADP ; this generates ATPs. The process is catalysed by the myosin enzyme myokinase.
In the second method, the enzyme creatine kinase obtains a phosphate ion from the molecule creatine phosphate and (donates) attaches it to an ADP to generate an ATP.
This fast phophagen system is a stop gap method that the body uses to supply the ATPs the muscles needs after the myoglobin stores of oxygen have been depleted, but under conditions of fairly vigorous exercise like fast walking, or fast swimming, this system can only stop the ATP gap for about one minute. After that the muscles turn to anaerobic fermentation until the cardiopulmonary system can supply enough oxygen for aerobic respiration and the production of an ample supply of ATP.
