The organelles discussed up to this point, particularly the endomembrane system, provide cells with some support. The cytoskeleton adds to this support, plays a role in cell movement, and may have a role in cell signaling. Microfilaments are solid rods composed of globular proteins. They play a role in cell movement, including contraction.
Intermediate filaments are ropelike strands of fibrous proteins.
These structures are tension bearing and anchor some organelles. Microtubules are hollow tubes composed of globular proteins. Microtubules guide the movement of organelles through the cell and are the basis of ciliary and flagellar movement.