undulipodium
undulipodium (pl. undulipodia) A slender flexible outgrowth of a eukaryote cell used for locomotion or propelling fluids over the surface of the cell. The term ‘undulipodium’ is used to designate a eukaryotic ‘flagellum’ or a cilium (which have the same structure), to emphasize the distinction between these structures and the flagellum of a bacterium. Many protoctists and sperm cells swim by means of undulipodia, and various organisms use them to establish feeding currents, or to clear debris from epithelial surfaces. All undulipodia have a shaft, about 0.25 μm in diameter, consisting of a longitudinal array of microtubules, the axoneme, which is surrounded by an extension of the cell's plasma membrane. The axoneme has two singlet microtubules running down the middle and nine doublet microtubules around the periphery, giving a characteristic 9 + 2 array. At its base the axoneme connects with a basal body (or kinetosome). This is a short cylinder that, like a centriole, consists of nine triplet microtubules; it organizes assembly of the axoneme microtubules and is part of a complex array of fibres and microtubules forming a root structure within the cell. Cilia are shorter than flagella, and move by a whiplike power stroke followed by a recovery stroke in the opposite direction. Flagella generate successive waves that pass from the base to the tail. In both cases, flexing of the shaft is produced by a sliding motion of the microtubule doublets relative to each other. This involves the successive formation and breakage of molecular bridges between adjacent doublets. The bridges are composed of a protein, dynein, and their formation requires energy in the form of ATP.
More From encyclopedia.com
Cytoskeleton , The cytoskeleton is responsible for cell shape, motility (movement) of the cell as a whole, and motility of organelles within a cell. There are three… Cell , Cell
The cell is the basic unit of a living organism. In multicellular organisms (organisms with more than one cell), a collection of cells that work… Cell Membrane , cell membrane (plasmalemma, plasma membrane, protoplast) A sheet-like membrane, 7.5–10 nm thick, that forms a selectively permeable barrier enclosing… Intermediate Filament , intermediate filament Any of numerous microscopic protein fibres that form part of the cytoskeleton of eukaryote cells. With a diameter of about 10 n… Cells , Cells
Plants are multicellular organisms composed of millions of plant cells. Although individual cells may differ greatly from each other in mature… Protozoan , protozoan (prō´təzō´ən), informal term for the unicellular heterotrophs of the kingdom Protista. Protozoans comprise a large, diverse assortment of m…
You Might Also Like
NEARBY TERMS
undulipodium