Chapter 9-Lecture 1

Chapter 9-Lecture 1 - THE CYTOSKELETON AND CELL MOTILITY...

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THE CYTOSKELETON AND CELL MOTILITY
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The cytoskeleton is composed of three well-defined filamentous structures- microtubules , microfilaments and intermediate filaments . Microtubules are rigid tubes composed of subunits of the protein tubulin. Microfilaments are solid, thinner structures composed f the protein actin Intermediate filaments are tough of the protein actin, Intermediate filaments are tough, ropelike fibers composed of a variety of similar proteins
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Fig. 9.1 An overview of the structure and functions of the cytoskeleton-
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Function of Cytoskeleton: 1. a scaffold , providing structural support that helps maintain . sc o d , p ov d g s uc u suppo e ps the shape of the cell. n ternal framework responsible for positioning the 2. An internal framework responsible for positioning the various organelles within the interior of the cell. 3. The machinery that moves materials and organelles within cells. 4. The force-generating apparatus that moves cells from one place to another . 5. A site for anchoring mRNAs and facilitating their translation into polypeptides 6. An essential component of the cells division machinery.
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The study of the cytoskeleton- The use of fluorescence microcopy The in situ study of the cytoskeleton is rgely accomplished by use of largely accomplished by use of fluorescence microscopy
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The machinery that moves materials and organelles within cells Peroxisome Fig. 9.2 An example of the role of microtubules in transporting organelles. The peroxisomes are shown in green and MT in red
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The use of video microscopy and in vitro otility assays to follow the activities of motility assays to follow the activities of molecular motors.
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A B D C a, bead coated with the motor protein kinesin b. the bead deposited on a microtubule d the bead binds to the microtubule and begins moving along the microtubule track Fig. 9.6a-d Using video microscopy to follow the activities of molecular Motors. Bead coated with with kinesin, a motor protein. c,d. the bead binds to the microtubule and begins moving along the microtubule track
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Kinesin Cargo Head portion Tail portion Fig. 9.6e Schematic diagram of the movement of one of the kinesin coated beads along a microtubule
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A control pigment cell from the amphibian Xenopus a pigment cell that is overexpressing a gene for a mutant motor protein The mutant protein acts as a competitive inhibitor of the ormal protein produced in the cell and inhibits pg p p showing the black pigment granules dispersed into the elongated cellular processes normal protein produced in the cell and inhibits dispersion of the pigment granules . This result points to the role of this motor protein in the outward transport of these membrane-bounded ranules Figure 9.7 Expression of a mutant motor protein inhibits the dispersion of pigment granules in a pigment cell granules
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Structure and composition of microtubules
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GDP et a b c 13 subunits TP beta GTP alpha The α/β heterodimer of tubulin.
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Chapter 9-Lecture 1 - THE CYTOSKELETON AND CELL MOTILITY...

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