ATP in the muscles, is replenished in three ways. Which of the following is not one of them ?
Breakdown of protein
All muscle cells produce adenosine triphosphate (ATP) molecules which are used to power the movement of the myosin heads. Muscles have a short-term store of energy, in the form of creatine phosphate, which is generated from ATP and can regenerate ATP when needed with creatine kinase.
Once the ATP and phosphocreatine stores are depleted, during intense muscle activity, anaerobic respiration kicks in.
Now the stored glycogen starts to be used; breakdown of glycogen to lactic acid starts to take place, to supply for the high ATP requirement. The lactic acid is later converted back to glucose in the liver.
Protein breakdown does not take place in muscle cells.