Question

Calcium is important in skeletal muscle contraction because it

• A. prevents the formation of bonds between the myosin cross bridges and the actin filament
• B. binds to troponin to remove the masking of active sites on actin for myosin.
• C. detaches the myosin head from the actin filament.
• D. activates the myosin ATPase by binding to it

Answer 1

Answer: (B)

•Signal for contraction increase $Ca ^{++}$ level many folds in the sarcoplasm.
• $Ca^{++} $ now binds with sub-unit of troponin (troponin $"C"$) which is masking the active site on actin filament and displaces the sub-unit of troponin.
•Once the active site is exposed, head of the myosin attaches and initiate contraction by sliding the actin over myosin.