What Allows Muscle Fibers to Shorten During Contraction

Question

What allows muscle fibers to shorten during contraction?
A) Individual protein filaments contract.
B) Cross-bridges between filaments break.
C) Arrays of filaments slide against each other.
D) Protein filaments coil more tightly.
E) Subunits of protein polymers detach.

Accepted Answer

Muscle fibers contract by the sliding filament mechanism, which involves the arrays of thin and thick filaments in the muscle fibers sliding past each other. This sliding is made possible by the interactions between the myosin heads of the thick filaments and the actin molecules of the thin filaments, forming cross-bridges that pull the actin filaments towards the center of the sarcomere. As these cross-bridges cycle and detach, the actin filaments slide further, shortening the sarcomere and resulting in muscle contraction. Therefore, option C, which states that arrays of filaments slide against each other, is the correct answer.