The cytoskeleton of a eukaryote - specifically of an animal cell, has three kinds of cytoskeletal filaments, which provide structure, aid in movement, and help with transport within the cell. Microtubules organize the positions of organelles and direct intracellular transport. Intermediate filaments are rope-like fibers found along the inner face of the nuclear envelope, and they also build cable networks connecting the cells of epithelial sheets. These filaments provide mechanical strength. Microfilaments, or actin filaments, are most concentrated right beneath the plasma membrane, at the so-called “cortex” of the cell, and they control the outer shape of the cell and are important in locomotion. Actin can form several kinds of cell surface projections, including microvilli, lamellipodia, and filopodia. These help move cells over solid substrates.
The three kinds of cytoskeleton filaments work in concert with countless accessary proteins, which attach the filaments to each other and to other cell components and direct their assembly, distribution, and disassembly. The cytoskeleton is not a static structure, but is dynamic, able to change or persist to suit the cell’s needs. This is because the cytoskeletal structures are composed of tiny polar subunits that can rapidly assemble and disassemble thanks to weak, noncovalent linkages into “polymers”. These macromolecular components of the cytoskeleton filaments are constantly in flux.
3D model of cell: www.turbosquid...
LINK TO VIDEO ON JUNCTIONS: • Epithelial Cell JUNCTIONS