Cells160-page21

Cells160-page21 - Centrioles are self-replicating. A...

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Cell - 21 Cilia and flagella Many cells can also generate external locomotion, either by moving their body through the medium, or by moving substances past the surface of their cell. Such locomotion is generated by cilia and flagella, structures formed from microtubules that are embedded in and extend through the plasma membrane into the external environment. They are coated with plasma membrane material. Eukaryotic cilia and flagella have an arrangement of microtubules, known as the 9 + 2 arrangement (9 pairs of microtubules (doublets) around the circumference of the cilium and 2 central microtubules). Flagella and Cilia Centrioles Cilia are generally small in length, and a ciliated cell will have many cilia. Flagella are relatively long, and cells will have one or very few. Cilia and flagella may originate from centrioles, also composed of microtubules. Centrioles consist of 9 groups of 3 microtubules (9 X 3 arrangement).
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Unformatted text preview: Centrioles are self-replicating. A flagellum or a cilium is formed from a basal body, which is identical to centrioles and is embedded in the plasma membrane. There is a transition zone where the two microtubules of the cilia/flagella join a third microtubule forming the basal body ring. (Some prokaryotic cells also have flagella, but their structure and mode of generating motion are very different from the eukaryotic flagella.) Pseudopodia External locomotion can also be generated by internal microfilaments that align to form lobes of cytoplasm called pseudopodia. Pseudopodia project outward in one direction while other regions of the cell contract, generating movement. Pseudopodia are also used to surround and capture prey, a process called phagocytosis. The protist Amoeba and white blood cells move by pseudopodia and feed by phagocytosis....
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This note was uploaded on 12/29/2011 for the course BIO 151 taught by Professor Edwards during the Spring '10 term at SUNY Stony Brook.

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