microtubule

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microtubule A tubular structure, 15–25 nm in diameter, of indefinite length, and composed of subunits of the protein tubulin. It occurs in large numbers in all eukaryotic cells, either freely in the cytoplasm, or as a structural component of organelles (e.g. cilia and flagella). Microtubules appear to function in the motility of cells, the maintenance of cell shape, and the transport of materials within cells. In addition, they form part of the structure of the mitotic spindle (responsible for the movement of chromosomes during cell division), and have been implicated in sensory transduction in some receptor cells.

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