What is the function of tropomyosin in muscle contraction?

What is the function of tropomyosin in muscle contraction?

• A. Inhibiting calcium ion influx
• B. Blocking myosin-binding sites on actin
• C. Facilitating ATP hydrolysis
• D. Enhancing muscle elasticity

Answer: (B)

Tropomyosin plays a crucial role in muscle contraction by blocking myosin-binding sites on actin. In a relaxed muscle, tropomyosin lies along the actin filaments, covering these binding sites and preventing the interaction between actin and myosin. This inhibition is essential for regulating muscle contraction; when calcium ions are released during muscle stimulation, they bind to troponin, which causes a conformational change that moves tropomyosin away from the myosin-binding sites. This allows myosin heads to bind to actin, facilitating the cross-bridge cycling that leads to muscle contraction. Therefore, the function of tropomyosin is vital for controlling when muscle contraction occurs by exposing or blocking the necessary binding sites on actin.

Tropomyosin plays a crucial role in muscle contraction by blocking myosin-binding sites on actin. In a relaxed muscle, tropomyosin lies along the actin filaments, covering these binding sites and preventing the interaction between actin and myosin. This inhibition is essential for regulating muscle contraction; when calcium ions are released during muscle stimulation, they bind to troponin, which causes a conformational change that moves tropomyosin away from the myosin-binding sites. This allows myosin heads to bind to actin, facilitating the cross-bridge cycling that leads to muscle contraction. Therefore, the function of tropomyosin is vital for controlling when muscle contraction occurs by exposing or blocking the necessary binding sites on actin.