Cytoskeleton - Microtubules rigid internal skeleton tracks...

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Cytoskeleton (86-90) - Maintains cell shape - Cellular movement - Positions organelles - Act as tracks for motor proteins - Interacts w/ extracellular structures (anchors cell) To see if A causes B, use drug to inhibit A and see if B still occurs, or look for cells that have mutated A and see if B still occurs apply to cytoskeleton and its functions Microfilaments (actin filaments) : movement, shape stabilization 7 nm diameter, several µm long, double helical chain, + and – ends Actin polymerization is reversible- can break down into free actin monomers Interaction between actin and myosin (motor protein) = muscle contraction Used in cytoplasmic streaming, “pinching” in cell division, pseudopodia Intermediate filaments : structure stabilization, resist tension 8-12 nm diameter, made of keratin Used to maintain organelle positions, hold up microfilaments in microvilli, maintain rigidity in tissues by connecting desmosomes between adjacent cells
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Unformatted text preview: Microtubules : rigid internal skeleton, tracks for motor proteins 25 nm diameter, several µm long, long/hollow/unbranched cylinder, + and - ends Assembled from tubulin (protein) dimers: α-tubulin and β-tubulin Tubulin dimers added/subtracted, usually at + end microtubules are dynamic structures Radiate from microtubule organizing center Used in plants to control cellulose cell wall arrangement, chromosome distribution in cell division, cilia and flagella Motor proteins carry materials in cell along microtubules Motor proteins : undergo reversible shape changes by ATP Dynein Moves to - end of microtubule Can change 3D shape Bound to one microtubule doublet and binds to neighboring doublet microtubules slide Kinesin Moves to + end of microtubule Carries vesicles/organelles Binds to organelle and walks along microtubule by changing shape...
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This note was uploaded on 04/17/2008 for the course BIO 121 taught by Professor Lampson,rea during the Fall '07 term at UPenn.

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