Microtubules - plasma membrane . Cells that contain cilia...

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Microtubules Microtubules are small cylindrical fibers that change in length by assembling (polymerizing) and disassembling (depolymerizing). They are made of a protein called tubulin. Tubulin dimers are arranged to form a long hollow cylinder. The fibers are lengthened and shortened as tubulin dimers assemble or disassemble from one or both ends of the filament. The assembly of microtubules in many cells is controlled by an area near the nucleus called the centrosome or microtubule organizing area. . Microtubules act as tracts along which organelles can move. For example, they are associated with movement of vesicles from the Golgi complex to the plasma membrane . Microtubules are responsible for the movement of cilia and flagella. They move the chromosomes during cell division. Cilia and Flagella Cilia and flagella are hairlike structures projecting from the cell that function to move the cell by their movements. They contain cytoplasm and are enclosed by the
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Unformatted text preview: plasma membrane . Cells that contain cilia are ciliated . Cilia are shorter than flagella but are similar in construction. Examples: Sperm use flagella to move. Many kinds of single-celled organisms such as the Paramecium in the photograph below move by cilia or flagella. The cilia can be seen covering the cell in the photograph. Cells lining the human upper respiratory tract are ciliated (have cilia). The cilia move mucous and debris upward to the mouth where it is swallowed. The photograph below is a cross section of a human trachea (400 X). Note the cilia on the upper surface. Eukaryotes have 9 doublets (pairs) of microtubules arranged in a circle around 2 central microtubules. This 9 + 2 pattern is characteristic of all eukaryotic cilia and flagella but not those of prokaryotes. The pairs of microtubules are cross-linked. The shifting positions of the cross-links move the cilia or flagella....
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This note was uploaded on 12/15/2011 for the course BIO BSC1010 taught by Professor Gwenhauner during the Fall '10 term at Broward College.

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Microtubules - plasma membrane . Cells that contain cilia...

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