Question

How does the troponin-tropomyosin complex affect cross-bridge cycling?

• A. When [Ca²⁺] is low, the troponin-tropomyosin complex blocks actin’s binding site for myosin. When [Ca²⁺] is high, the complex rolls out of they way, allowing myosin to bind to actin and initiate the cross-bridge cycle.
• B. The troponin-tropomyosin complex regenerates ATP for the myosin ATPase.
• C. The troponin-tropomyosin complex regulates calcium release form the terminal cisternae.
• D. The troponin-tropomyosin complex binds to the myosin head, facilitating contact with the actin filaments

Answer 1

Answer: (A)

When $Ca²⁺$ is low, the troponin-tropomyosin complex blocks actin’s binding site for myosin. When $Ca²⁺$ is high, the complex rolls out of they way, allowing myosin to bind to actin and initiate the cross-bridge cycle.