Which of the following is true about muscle structure?
Correct answer: B. Actin filaments are arranged so that six actin filaments surround each myosin filament.
- A. Myofibrils make up about 15% of the contents of a muscle fiber.
- B. Actin filaments are arranged so that six actin filaments surround each myosin filament.
- C. Both A and B are correct
- D. None of these
Explanation
Six actin filaments surround each myosin filament, producing a hexagonal array. Muscle fibers can contain up to a few thousand myofibrils, which make up about 85% of the content of a muscle fiber. Therefore, B is correct.
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About Support and Movement
Support and movement covers the axial and appendicular skeleton, bone structure, joints and the arrangement of skeletal muscles. Muscle contraction is explained through actin, myosin, sliding filaments, calcium ions and ATP, while arthritis is distinguished as a disorder of joints rather than a normal part of movement.
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