How many actin filaments surround the myosin at each end?
Correct answer: C. 6
- A. 2
- B. 4
- C. 6
- D. 8
Explanation
In a muscle sarcomere, each myosin filament (thick filament) is surrounded by 6 actin filaments (thin filaments) at each end. This arrangement allows for the sliding filament theory of muscle contraction, where the myosin heads bind to the actin filaments and pull them towards the center of the sarcomere, resulting in muscle contraction.
This question appeared on the KMU MDCAT 2023 (retake) paper, which you can sit online with every answer explained.
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About Muscles
Muscles covers skeletal, smooth and cardiac muscle, their microscopic structure and the roles of tendons, myofibrils, actin and myosin. It explains the sliding filament mechanism, sarcomere shortening, neuromuscular transmission and calcium regulation, while distinguishing voluntary skeletal movement from involuntary contraction in smooth and cardiac muscle.
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