Question

multiple choice question

what happens when calcium ions bind to troponin?

tropomyosin moves off the active site on actin.
troponin binds to myosin.
the myosin head binds to tropomyosin.

Explanation:

Calcium binding to troponin

Using the Troponin Function and Muscle Contraction Initiation knowledge points

• Calcium ions (\(\text{Ca}^{2+}\)) bind directly to troponin during excitation-contraction coupling.
• This binding induces a conformational change in the troponin complex.

Shift of tropomyosin

Using the Tropomyosin Regulation knowledge point

• The structural change in troponin pulls the attached tropomyosin molecule.
• This movement shifts tropomyosin away from the active (myosin-binding) sites on the actin filament, exposing them for cross-bridge formation.

Answer:

• Tropomyosin moves off the active site on actin. (Correct answer)
• Troponin binds to myosin.
• The myosin head binds to tropomyosin.