Which type of myofilaments is thick in structure?

Myosin is the thick myofilament responsible for muscle contraction. In muscle fibers, myosin molecules are organized into thick filaments, which are essential for the sliding filament model of muscle contraction. The structure of myosin allows it to effectively interact with actin, the thinner myofilament, facilitating the movement that leads to muscle contractions.

Myosin molecules have a long tail and a globular head that can bind to actin and hydrolyze ATP, providing the energy necessary for contraction. This interaction is critical for the functionality of striated muscle and plays a significant role in generating force.

In contrast, actin is the thin myofilament that works in coordination with myosin. Sarcomeres are the basic structural and functional units of muscle tissue composed of both thick and thin filaments. Filamentous does not refer specifically to a type of myofilament but rather describes a form or structure of fibers in general.