During the contraction cycle of a mammalian skeletal muscle fiber, the binding of calcium ions to which regulatory protein triggers the exposure of myosin-binding sites on actin filaments?

💡 Solution & Explanation

Calcium ions released from the sarcoplasmic reticulum bind to troponin, causing a conformational shift in tropomyosin that uncovers the myosin-binding sites on actin filaments, allowing cross-bridge formation. Sliding filament theory explains muscular contraction mechanics. ATP provides energy for the power stroke.