Which protein functions as a motor protein that applies the power stroke during skeletal muscle contraction?

• A. Troponin
• B. Myosin
• C. Actin
• D. Tropomyosin

Answer: (B)

Verified step by step guidance

1. Step 1: Begin by understanding the context of skeletal muscle contraction. Skeletal muscle contraction is a process that involves the sliding filament mechanism, where actin and myosin filaments interact to produce movement.
2. Step 2: Identify the role of motor proteins in this process. Motor proteins are responsible for generating force and movement by converting chemical energy (from ATP) into mechanical work.
3. Step 3: Examine the specific proteins listed in the problem: Troponin, Myosin, Actin, and Tropomyosin. Understand their roles in muscle contraction: Troponin regulates the interaction between actin and myosin, Tropomyosin blocks the binding sites on actin, Actin forms the thin filaments, and Myosin is the motor protein responsible for the power stroke.
4. Step 4: Focus on Myosin's function. Myosin heads bind to actin filaments and, through ATP hydrolysis, perform a conformational change known as the 'power stroke,' which pulls the actin filaments and causes muscle contraction.
5. Step 5: Conclude that Myosin is the motor protein that applies the power stroke during skeletal muscle contraction, as it directly generates the mechanical force required for movement.