Question

Which of the following is NOT a true statement about the myofilaments responsible for contracting and relaxing muscles?

A. For body movement to happen, myosin and actin must float away from one another to expand the muscle.

B. Actin are relatively thin strands of protein that attach to one end or the other of the sarcomere.

C. Myosin are relatively thick strands of protein and are studded with heads resembling knobs.

D. In a sarcomere, strands of myosin float between strands of actin.

Answer 1

Answer A is not true because during muscle contraction, myosin and actin slide past one another to shorten the sarcomere, not float away; this is known as the sliding filament model.

Step-by-step explanation:

The correct answer is that Statement A is NOT true about the myofilaments responsible for contracting and relaxing muscles.

It's not that myosin and actin must float away from one another to expand the muscle; instead, for a muscle to contract, myosin heads on thick filaments bind to actin on thin filaments and pull them closer together, shortening the sarcomere. The myosin and actin do not change in length or float away from each other; they slide past one another due to the formation and breaking of cross-bridges. This process is known as the sliding filament model of muscle contraction.