Concept: Different elements of the cytoskeleton are responsible for different types of cellular movement.

Solution: Microfilaments are extremely thin, flexible fibers made of the protein actin. They are directly responsible for cellular movements involving the plasma membrane and cytoplasm, such as amoeboid movement (pseudopodia), muscle contraction, and cyclosis (cytoplasmic streaming).

Distractor Autopsy: Microtubules (tubulin) are rigid and handle flagella/cilia and spindle fibers. Intermediate filaments provide static structural tension, not movement.