Muscle contraction Quiz
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5 questions, one answer each
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1. Which event occurs first in the contraction of a muscle fibre?
- A. Myosin heads bind to actin
- B. Calcium ions are released from the sarcoplasmic reticulum
- C. ATP is hydrolysed by ATPase
- D. Tropomyosin moves back over actin
2. What is the role of ATP binding to a myosin head?
- A. Detachment of the head from actin
- B. Exposure of the myosin-binding sites
- C. Release of calcium ions
- D. Movement of the actin filament
3. Which statement about the sarcomere in a contracting muscle is correct?
- A. The A band gets shorter
- B. The I band gets longer
- C. The filaments slide past each other and the A band stays the same length
- D. The myosin filaments shorten
4. What is the function of phosphocreatine in muscle?
- A. It binds to myosin heads so they detach
- B. It stores calcium ions
- C. It covers the binding sites on actin
- D. It donates phosphate to ADP to regenerate ATP
5. A muscle uses ATP at 6 mmol kg⁻¹ s⁻¹ and has 3 mmol kg⁻¹ ATP and 21 mmol kg⁻¹ phosphocreatine. For how long do the stores last?
- A. 2 s
- B. 4 s
- C. 6 s
- D. 3.5 s