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MBBS QUESTION #10233
Question 1
Skeletal muscle contraction is triggered when calcium released from the sarcoplasmic reticulum binds to which regulatory protein, causing a conformational shift that exposes the myosin-binding site on actin?
  • Tropomyosin
  • Troponin C✔️
  • Titin
  • Nebulin
Correct Answer Explanation
Calcium binds troponin C, causing troponin to shift tropomyosin away from the myosin-binding sites on actin filaments, allowing cross-bridge cycling to proceed — the molecular basis of excitation-contraction coupling in skeletal muscle.