When the muscle is required to contract, calcium ion binds with _ molecule and causes them to move slightly.
Correct answer: C. Troponin
- A. Actin
- B. Myosin
- C. Troponin
- D. Tropomyosin
- E. ATP
Explanation
Troponin is a complex of three proteins that are involved in muscle contraction. When calcium ions bind to the troponin complex, it causes a change in the complex that moves the tropomyosin molecule slightly, exposing the myosin-binding sites on the actin filament. This allows the myosin head to bind to the actin filament, sliding the actin and myosin filaments past each other, leading to muscle contraction.
This question appeared on the NUMS 2019 (cancelled sitting) paper, which you can sit online with every answer explained.
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About Muscle Contraction
Muscle contraction is explained by the sliding filament model, in which myosin heads pull actin filaments within sarcomeres using ATP. The topic covers calcium, troponin, tropomyosin, the neuromuscular junction and relaxation, with attention to how filament length stays almost constant while the sarcomere shortens.
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