The cytoskeleton is a protein scaffold required for support , internal organization , and even movement of the cell Microfilaments are the most abundant cytoskeletal component . They are composed of a protein called actin that forms ropelike threads with a diameter of about 7 nm . 7.2Microtubules are composed of a protein called tubulin . They have a diameter of about 22 nm . Intermediate filaments have diameters of approximately 10 nm . They line the inside of the nuclear envelope and extend outward to the cell membrane .