Muscle contraction Quiz
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5 questions, one answer each
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1. Which protein covers the myosin-binding sites on actin in a resting muscle?
- A. Troponin
- B. Myosin
- C. Tropomyosin
- D. ATPase
2. What causes the myosin head to detach from actin?
- A. Binding of Ca²⁺
- B. Binding of ATP
- C. Release of ADP
- D. Movement of tropomyosin
3. Which change occurs in a sarcomere when a muscle contracts?
- A. The A band shortens
- B. The I band shortens
- C. The myosin filaments shorten
- D. The actin filaments shorten
4. Which sequence is correct after an action potential reaches the fibre?
- A. Ca²⁺ bind troponin, tropomyosin moves, cross-bridges form
- B. Ca²⁺ bind myosin, tropomyosin moves, cross-bridges form
- C. Ca²⁺ bind tropomyosin, troponin moves, ATP binds actin
- D. ATP binds actin, Ca²⁺ bind troponin, tropomyosin moves
5. A drug stops ATP being hydrolysed by myosin. What is the immediate effect?
- A. Ca²⁺ cannot be released
- B. Tropomyosin cannot move
- C. Myosin heads cannot return to their original position to repeat the cycle
- D. Actin filaments shorten