Question

Physical evidence that supports the sliding filament theory includes decreased distance between the z-discs during contraction.

True/False.

Answer 1

The answer would be True. The sliding filament theory suggests that during muscle contraction, the thin actin filaments slide past the thick myosin filaments, causing the z-discs to come closer together. This results in a decrease in the distance between the z-discs.

Answer 2

The statement is true as the sliding filament theory suggests that the Z lines come closer together during muscle contraction due to the pulling of actin filaments by myosin filaments, which shortens the sarcomere.

Step-by-step explanation:

The statement Physical evidence that supports the sliding filament theory includes decreased distance between the z-discs during contraction is true. The sliding filament theory explains muscle contraction through the interaction of myosin and actin filaments. During this process, the myosin filaments use energy from ATP to pull the actin filaments closer together, thus drawing the Z lines closer and shortening the sarcomere.

Notably, during contraction, the H zone and the I band decrease in size, but the width of the A band remains unchanged. This is because the sarcomere's structure changes not by shortening the length of the filaments themselves but rather by allowing them to slide past each other. As a result, the Z lines, which are at the ends of each sarcomere, move closer together due to the inward sliding movement of the actin filaments.