Final answer:
The myosin tail portion of myosin II molecules allows them to form the structural backbone of thick filaments, essential in muscle contraction. Myosin heads bind to actin, sliding past them due to ATPase activity, while tropomyosin and troponin regulate this process.
Step-by-step explanation:
In muscle cells, myosin II is a key contractile protein that interacts with actin to facilitate muscle contraction. Specifically, the structural component of myosin II that allows it to form filaments is the myosin tail. Multiple myosin molecules connect via their tails to create the thick filament's backbone, which is centered near the M line of the sarcomere. Meanwhile, the myosin heads are responsible for binding to actin and truly powering the contraction through their ATPase activity.
The actin and myosin filaments slide past each other to shorten the muscle fiber and provoke movement or force. This sliding filament model is a foundational concept in understanding muscle contraction. Finally, regulatory proteins such as tropomyosin and troponin modulate the interaction between myosin and actin, ensuring controlled muscle contraction responses