Question

The role of calcium in muscle contraction is

• A. To break the cross bridges as a cofactor in the hydrolysis of ATP
• B. To bind with troponin, changing its shape so that the actin filament is exposed
• C. To transmit the action potential across the neuromuscular junction
• D. To re-establish the polarization of the plasma membrane following an action potential

Answer 1

The correct option is B To bind with troponin, changing its shape so that the actin filament is exposed

• The muscle contraction cycle is triggered by calcium ions binding to the protein complex troponin, exposing the active-binding sites on the actin.
  
• ATP then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.

So, the correct option is 'to bind with troponin, changing its shape so that the actin filament is exposed'.