Which protein, along with actin, forms the bands in muscle sarcomeres?

The correct answer is myosin, which plays a crucial role in muscle contraction alongside actin. In the sarcomere, the structural and functional unit of muscle tissue, actin and myosin interact to facilitate muscle contraction. Myosin has a crucial part in this process because it forms thick filaments that work with the thin filaments of actin to produce tension.

When a muscle fiber receives a signal to contract, myosin heads attach to binding sites on the actin filaments, pulling them toward the center of the sarcomere in a movement known as the power stroke. This sliding mechanism is fundamental to muscle movement and is responsible for the striated appearance of skeletal and cardiac muscle, which is characterized by alternating light and dark bands created by the arrangement of myosin and actin.

Other proteins mentioned do not participate in the formation of bands in sarcomeres. Dynein is primarily known for its role in cellular transport and movement, such as in the functioning of cilia and flagella. Keratin is a structural protein found in hair, nails, and the outer layer of skin, providing protection and structure but not involvement in muscle contraction. Collagen is a structural protein that provides strength and support in connective tissues but does