Final answer:
Creatine phosphate provides the energy needed to synthesize ATP, replenishing the cell's energy currency to power muscle contractions at the onset of activity. The correct option is C.
Step-by-step explanation:
Creatine phosphate supplies energy for the synthesis of ATP. This molecule stores energy within its phosphate bonds, which can be quickly utilized when a muscle contracts and requires immediate energy. During rest, excess ATP transfers energy to creatine, forming ADP (adenosine diphosphate) and creatine phosphate.
When energy demand increases, as in muscle contraction, creatine phosphate donates its phosphate group back to ADP, regenerating ATP and releasing creatine in the process. This reaction, catalyzed by the enzyme creatine kinase, provides a rapid supply of ATP to power muscle contractions briefly before other energy sources are tapped.
It should be noted that ATP breakdown, or hydrolysis, releases energy, whereas creatine phosphate's role is to supply the energy for ATP synthesis, not for its breakdown. Consequently, creatine phosphate is crucial in the initial stages of high energy demands, such as the onset of physical activities.