BIS104 Slide10

BIS104 Slide10 - Lecture 10 The Cytoskeleton Overview of...

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Lecture 10 The Cytoskeleton
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Overview of Cytoskeleton A. Responsible for overall shape, structure and movement (cillia in the lung and microvilli in the gut) of the cell B. Internal organization of the cell ( secretory pathway, chromosome segregation, positioning the organelles ) Red : actin; green : microtubules C. Provide mechanical strength and resistance to shear Figure 16-1 Molecular Biology of the Cell (© Garland Science 2008)
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Forms a highly dynamic structure that can re-organize as cell changes shape, divides and responds to environment Figure 16-7 Molecular Biology of the Cell (© Garland Science 2008)
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Cytoskeleton are dynamic and adaptable -A Neutrophil chasing bacteria as an example
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Figure 16-5 Molecular Biology of the Cell (© Garland Science 2008) Cytoskeleton can also form stable structures
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Three classes of cytoskeletal filaments Microtubules: Intracellular transport (vesicles, organelles), mitosis (chromosome segregation) Actin filaments: Determine a cell’s shape, locomotion, cytokenesis Intermediate filaments: Provide mechanical strength and resistance to shear
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Figure 16-10 Molecular Biology of the Cell (© Garland Science 2008) The cytoskeleton is highly dynamic and adaptable Filaments are made from a pool of free subunits. There is an equilibrium between monomers and filaments -is highly regulated by accessory proteins in the cells Nucleation (is the rate limiting step in polymer formation) -the initial process of the initial aggregates assembly -essential for forming a large filaments short oligomers can form spontaneously but very unstable
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The cytoskeleton is highly dynamic and adaptable At critical concentration (Cc): the rate of subunit addition is equal to the rate of subunit loss Cc = Critical concentration K on = rate constant for the addition of one subunit K off = rate constant for the loss of one subunit K on is dependent on the conc of free subunits (C) K off is independent of the cocn of free subunits FYI: (A+B-->AB, at equilibrium: Kon[A][B]=Koff [AB], K=[AB]/[A][B]=K on /K off ) Cc K on = K off Cc = K off / K on = 1/K=Kd Critical concentration
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Figure 16-11 Molecular Biology of the Cell (© Garland Science 2008) Microtubules - globular α -tubulin and β -tubulin make up MT - bind GTP ; α -tubulin always bind to GTP whereas β -tubulin cycles between GTP (active) and GDP (inactive) 13 polar protofilaments form a MT, (more stable) - filaments and MT are Polar: α -tubulin faces the “ - ” end β -tubulin faces the “ + ” end
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Figure 16-12 Molecular Biology of the Cell (© Garland Science 2008) Actin filaments -globular actin monomers make up AF - bind ATP and cycles between ATP and ADP - two protofilaments form a helical AF -both the protofilament and AF are polar with a “+” and a “-” end
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Figure 16-13 Molecular Biology of the Cell (© Garland Science 2008) Plus and minus ends of filaments (MT, AF) have different rate constant It is easier for a subunit to bind to the plus end {Kon (+)>>Kon(-)} polymer
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This note was uploaded on 03/02/2010 for the course ECL 242 taught by Professor Holly during the Winter '10 term at UC Davis.

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BIS104 Slide10 - Lecture 10 The Cytoskeleton Overview of...

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