NEET 2018 · BiologyPrevious Year Question
Calcium is important in skeletal muscle contraction because it
Answer: (C) Binds to troponin to remove the masking of active sites on actin for myosin.. Answer: C.
- A.Detaches the myosin head from the actin filament.
- B.Activates the myosin ATPase by binding to it.
- C.Binds to troponin to remove the masking of active sites on actin for myosin.✓
- D.Prevents the formation of bonds between the myosin cross bridges and the actin filament.
Correct Answer
(C) Binds to troponin to remove the masking of active sites on actin for myosin.
Solution & Explanation
Answer: C. A neural signal causes release of Ca into the sarcoplasm; the increased Ca binds a subunit of troponin on the actin filament, which removes the masking of the active sites for myosin. The myosin head can then bind these exposed sites to form a cross bridge, initiating contraction. NCERT Ch 17, p.222, line 15: "Ca++ level leads to the binding of calcium with a subunit of troponin on"
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