Question

Which statement below most accurately describes the roles of the proteins actin and myosin during muscular contraction?

A. Both actin and myosin shorten, causing the muscle tissue to contract.
B. Both actin and myosin catalyze the reactions that result in muscle contraction
C. Actin molecules are disassembled by myosin, leading to a shortening of muscle sarcomeres.
D. Bridges between actin and myosin form, break, and reform, leading to a shortening of muscle sarcomeres.

Answer 1

The correct answer is option D. Actin and myosin interact through cross-bridge formation, where myosin heads pull on actin, resulting in the shortening of sarcomeres and muscle contraction.

Step-by-step explanation:

The roles of the proteins actin and myosin during muscular contraction involve several complex interactions. Actin and myosin do not shorten during the process. Instead, myosin filaments bind to actin filaments to form cross-bridges. The myosin heads then pull the actin filaments toward the center of the sarcomere, powered by energy from ATP, causing the sarcomere to shorten and the muscle to contract. This process is repeated in a cycle, where cross-bridges form, break, and reform, allowing the actin filaments to slide past the myosin filaments, thereby shortening the sarcomeres and leading to muscle contraction.

Therefore, the answer to the student's question is: "D. Bridges between actin and myosin form, break, and reform, leading to a shortening of muscle sarcomeres."