Creatine phosphate is primarily used for activities lasting less than 15 seconds. Which of the following best describes this use?

Creatine phosphate is primarily used for activities lasting less than 15 seconds. Which of the following best describes this use?

• A. Over an hour
• B. <15 seconds
• C. Hours
• D. Several minutes

Answer: (B)

The main idea is that the ATP–PCr (creatine phosphate) system fuels the very first, explosive bursts of activity. Muscle stores phosphocreatine (PCr) and a small amount of ATP. During a short, high-intensity effort, PCr donates its phosphate to ADP to rapidly regenerate ATP, which powers muscles for immediate work. Because PCr stores are limited, this system can sustain maximal effort for only about 10 to 15 seconds before depletion. After that, energy comes from other systems such as glycolysis and then oxidative phosphorylation for longer tasks. So describing this use as activities lasting less than about 15 seconds matches the ATP–PCr system’s role. Longer durations (over an hour, hours, or several minutes) rely on those other energy pathways.

The main idea is that the ATP–PCr (creatine phosphate) system fuels the very first, explosive bursts of activity. Muscle stores phosphocreatine (PCr) and a small amount of ATP. During a short, high-intensity effort, PCr donates its phosphate to ADP to rapidly regenerate ATP, which powers muscles for immediate work. Because PCr stores are limited, this system can sustain maximal effort for only about 10 to 15 seconds before depletion. After that, energy comes from other systems such as glycolysis and then oxidative phosphorylation for longer tasks. So describing this use as activities lasting less than about 15 seconds matches the ATP–PCr system’s role. Longer durations (over an hour, hours, or several minutes) rely on those other energy pathways.