Which protein covers the myosin binding sites on actin?

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Prepare for the ECPI Anatomy and Physiology AandP Exam 1. Utilize multiple choice questions and flashcards with detailed explanations. Enhance your knowledge and be exam-ready!

Multiple Choice

Which protein covers the myosin binding sites on actin?

Explanation:
Tropomyosin blocks the myosin-binding sites on actin in relaxed muscle. It runs along the grooves of the actin filament, covering those sites so myosin heads can’t attach. When calcium levels rise, the troponin complex binds calcium and shifts tropomyosin away from the binding sites, exposing them for cross-bridge formation and contraction. Actin is the filament itself, not the covering; myosin is the motor protein that would bind if the sites are exposed; troponin regulates the position of tropomyosin in response to calcium.

Tropomyosin blocks the myosin-binding sites on actin in relaxed muscle. It runs along the grooves of the actin filament, covering those sites so myosin heads can’t attach. When calcium levels rise, the troponin complex binds calcium and shifts tropomyosin away from the binding sites, exposing them for cross-bridge formation and contraction. Actin is the filament itself, not the covering; myosin is the motor protein that would bind if the sites are exposed; troponin regulates the position of tropomyosin in response to calcium.

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