Within a sarcomere, which structure is the thick filament?

Within a sarcomere, which structure is the thick filament?

• A. Actin
• B. Myosin
• C. Z-line
• D. Tropomyosin

Answer: (B)

Thick filaments in a sarcomere are composed of myosin. Myosin molecules align to form a central, rod-like filament with globular heads that extend outward to form cross-bridges with the actin filaments of the thin filament. These cross-bridges enable the sliding of filaments that shortens the sarcomere during contraction. The other components—actin as the thin filament (with tropomyosin regulating access to binding sites) and the Z-lines that define the sarcomere’s boundaries—play different roles and are not the thick filament. So the structure that makes up the thick filament is myosin.

Thick filaments in a sarcomere are composed of myosin. Myosin molecules align to form a central, rod-like filament with globular heads that extend outward to form cross-bridges with the actin filaments of the thin filament. These cross-bridges enable the sliding of filaments that shortens the sarcomere during contraction. The other components—actin as the thin filament (with tropomyosin regulating access to binding sites) and the Z-lines that define the sarcomere’s boundaries—play different roles and are not the thick filament. So the structure that makes up the thick filament is myosin.