Cross bridges have actin binding sites that are normally covered by troponin and tropomyosin except during excitation-contraction coupling.

Question

Quizplus · Accepted Answer

During excitation-contraction coupling, tropomyosin, not troponin, covers the actin binding sites. Troponin binds calcium, causing a conformational change that moves tropomyosin away from the binding sites, allowing cross-bridge formation.

Cross Bridges Have Actin Binding Sites That Are Normally Covered