[Campbell Biology P.1178] According to Figure 50.31, in which processes is ATP directly utili... | Practice Question

According to Figure 50.31, in which processes is ATP directly utilized during skeletal muscle contraction and relaxation?

  • A: Myosin cross-bridge formation.
  • B: Propagation of action potential along the plasma membrane.
  • C: Myosin cross-bridge breakdown and filament sliding.
  • D: Active transport of Ca2+ back into the sarcoplasmic reticulum.

Explanation

Figure 50.31 explicitly shows ATP being used for two key processes: Step 5, 'Cycles of myosin cross-bridge formation and breakdown, coupled with ATP hydrolysis, slide the thin filament toward the center of the sarcomere,' and Step 6, 'After the action potential ends, cytosolic Ca2+ is removed by active transport into the SR,' where the ATP symbol is directly shown alongside the Ca2+ pump.