Distinguish between the following cytoskeletal fibers:microtubules, microfilaments and intermediate filaments. Be sure to include their subunits, structure and major functions.
microtubules (MT): hollow tubes, maintenance of cell shape, cell motility, chromosome movements in cell division, organelle movements, subunit-tubulin dimers. microfilaments (MF): two intertwined strands of actin, maintenance of cell shape, changes in cell shape, muscle contraction, cytoplasmic contraction, cell motility, cell division, subunit-actin. intermediate filaments: fibrous proteins supercoilded into thicker cables, maintenance of cell shape, anchorage of nucleus and certain other organelles, formation of nuclear lamina, subunit-keratin protein.