His20051020 - The Cytoskeleton the elements of cytoskeleton...

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The Cytoskeleton - the elements of cytoskeleton are in dissolve state of monomers which normally dispersed in the cytosol. - It’s a complex network of microtubules, microfilaments, and intermediate filaments. These structure proteins provide for the rigidity and shape of the cells and also play an important role in the movements of organelles and intracytoplasmic vesicles. - The cytoskeleton also participates in the movement of entire cells. * stress fiber = microfilaments Microtubules - Each microtubule is composed of 13 protofilaments of alternating α and β tubulins. - The heterodimers of α and β tubulin subunits arranged into microtubule. (Figure 6-4) - Microbubules can be found in cytoplasm and usually utilized temporarily and dispersed into monomers. - During Mitosis, the microtubules are arranged into mitotic spindles. - Microtubules provide the basis for several complex cytoplasmic components, including centrioles, basal bodies, cilia, and flagella. These microtubules are usually in pairs (heterodimers) ,and are most stable.
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Fig. 6-4 - Microtubules are mostly found in eukaryotic cells. - The stability of microtubules varies, however, the mitotic spindles are not stable. - Colchicine , by blocking the assembly process, produces depolymerization of the microtubules. - Tubulin in formation of microtubules is a specifically orientated process. - Due to hydrolysis of GTP , the dimmers from tubulin pool in cytosol can polymerize and elongate the microtubule. - The mechanical function for the microtubules is form the shape of the cell as the cell processes independent of microtubules. This function is particularly apparent during cell differentiation in nerve cell; and the polarity of directional lining of cultural cell is also depends on microtubules. These structures are important in transporting molecules such as granules, and vesicles within the cell. They play roles in construction of mitotic spindles, movements of chromosomes in centrioles, as well as cilia and flagella motion. -
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- Microtubulins are engaged in formation of centrioles. Centrioles - are cylindrical structures composed primarily of high organized microtubules. - each centriole is composed of 9 sets of microtubule triplets arranged in the fashion of pinwheel. - centriole in pairs,the long axes of the centrioles are at right angle to each other. - during beginning of mitosis, the centriole pairs migrate to the opposite poles of the cell and become organizing centers ( organizing center for microtubules ) for the developing mitotic spindles. - centrioles are autonomic structure; new contrioles arises from replication during s period of interphase of cell division. New centrioles are produced form procentrioles, which is perpendicular to the parent centriole, in nucleation. - in the centrioles, the mitotic spindle formation is induced.
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This note was uploaded on 04/01/2008 for the course DENT Basic Hist taught by Professor Tulishka during the Spring '08 term at University of Michigan.

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His20051020 - The Cytoskeleton the elements of cytoskeleton...

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