microtubule

views updated

microtubule A tubular structure, 15–25 nm in diameter and of indefinite length, that is 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. centrioles, 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 and have been implicated in sensory transduction in some receptor cells.

More From encyclopedia.com