UNC-Chapel Hill BIOL 205 - Lecture 11 - The microtubule cytoskeleton (35 pages)

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Lecture 11 - The microtubule cytoskeleton



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Lecture 11 - The microtubule cytoskeleton

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Lecture Notes


Pages:
35
School:
University of North Carolina at Chapel Hill
Course:
Biol 205 - Cellular and Developmental Biology
Cellular and Developmental Biology Documents

Unformatted text preview:

02 11 09 Lecture 11 The microtubule cytoskeleton The cytoskeleton Gives the cell its shape Allows the cell to organize its components Produces large scale movements I e muscle contraction cell crawling propulsion via cilia and flagella The cytoskeleton is composed of networks of 3 different filaments Cytoskeletal filaments exhibit different physical properties The cytoskeleton is dynamic Microtubules are organized to perform specific functions What do microtubules do Establish an internal polarity to movements and structures in the interphase cell Participate in chromosome segregation during cell division Establish cell polarity during cellular movement Produce extracellular movement via beating of cilia and flagella Microtubule structure Microtubules exhibit a behavior termed dynamic instability Total mass of polymerized tubulin remains constant but individual microtubules are dynamic Growth assembly of microtubule Shrinkage disassembly of microtubule Catastrophe switching from growth to shrinking Rescue switching from shrinking to growth QuickTime and a Graphics decompressor are needed to see this picture Tubulin subunit addition takes place predominantly at the plus end Growing microtubules have a cap of GTP at the plus end Microtubule associated proteins MAPs can function as cross bridges connecting microtubules They can affect microtubule rigidity and assembly rate The centrosome is the primary microtubule nucleation site in most cells Centrosomes act to polarize the microtubule network Plus end fast growing usually in the cytoplasm Minus end slow growing anchored at the centrosome in most cells Centrosome duplication occurs once per cell cycle Centrosomes are often abnormal in cancer cells Why are microtubules dynamic Microtubule dynamics allow the cell to quickly reorganize the network when building a mitotic spindle Dynamics also allow microtubules to probe the cytoplasm for specific objects and sites on the plasma membrane search and capture Search and



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