What is the consequence if the myosin heads cannot bind to the actin during muscle contraction?

• A. Muscle contraction will not occur.
• B. The sarcomere will shorten.
• C. ATP will not be hydrolyzed.
• D. Calcium ions will not be released from the sarcoplasmic reticulum.

Answer: (A)

Verified step by step guidance

1. Understand the role of myosin and actin in muscle contraction: Myosin heads bind to actin filaments to form cross-bridges, which are essential for muscle contraction.
2. Recognize the importance of calcium ions: Calcium ions bind to troponin, causing a conformational change that moves tropomyosin away from the binding sites on actin, allowing myosin heads to attach.
3. Consider the role of ATP: ATP is necessary for the myosin heads to detach from actin and re-cock for another cycle of binding and pulling, which is crucial for muscle contraction.
4. Analyze the consequence of myosin heads not binding to actin: If myosin heads cannot bind to actin, cross-bridge formation does not occur, preventing muscle contraction.
5. Evaluate the impact on the sarcomere and ATP: Without cross-bridge cycling, the sarcomere will not shorten, and ATP will not be hydrolyzed as there is no detachment and re-cocking of myosin heads.