What do muscles use stored ATP for?

• A. Energy
• B. Calcium buffering
• C. Nerve conduction
• D. Protein synthesis

Answer: (A)

Muscles use stored ATP as the immediate energy source for contraction. ATP provides the energy that powers the myosin heads during the cross-bridge cycle—myosin binds actin, performs the power stroke, and then releases when another ATP molecule binds. This energy-driven cycling shortens the sarcomere and produces force. The amount of ATP stored in muscle is small, so it lasts only a few seconds of intense activity; phosphocreatine quickly regenerates ATP from ADP to keep contractions going, with longer-term ATP supplied by glycolysis and oxidative phosphorylation. Other roles listed, like calcium handling, nerve signaling, or protein synthesis, involve ATP too but aren’t the primary reason muscles carry this immediate, stored energy reserve for a brief burst of activity.