Question

Binding of Ca²⁺ to the TnC subunit of troponin leads to the uncovering of myosinbinding sites on actin (thin filaments). True or False?

Answer 1

The statement is true; Ca²⁺ binding to the TnC subunit of troponin facilitates the exposure of myosin-binding sites on actin by moving tropomyosin out of the way.

Step-by-step explanation:

True. The binding of Ca²⁺ ions to the TnC subunit of troponin causes a conformational change that leads to the relocation of tropomyosin, exposing myosin-binding sites on actin filaments. Initially, in resting muscle, the myosin-binding sites are obscured by tropomyosin, which is held in place by the troponin complex with subunits like troponin I (inhibitory troponin). When Ca²⁺ binds to troponin C, tropomyosin is moved away, and actin and myosin can form cross-bridges, initiating muscle contraction.