Lecture 7.Feb3 - BIO 311C Spring 2010 Lecture 7 Wednesday 3...

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Unformatted text preview: BIO 311C Spring 2010 Lecture 7 Wednesday 3 Feb. 2010 Prokaryotic cells contain structures that are very similar to structures of the eukaryotic cytoskeleton. Prokaryotic cytoskeletal elements are required for cell division, maintaining non-spherical cell shapes and separating plasmids from each other. Cross-sectional View of a Flagellum or Cilium 9 microtubule doublets 2 central microtubules plasma membrane dynein (a motor molecule) From textbook Fig. 6.24, p. 115 digramatic representation electron microscope picture cilia and flagella appear identical in cross-sectional view * Mechanism of movement of Flagella and Cilia a. Energy in the form of ATP is directed to a motor molecule called dynein. b. Energized dynein causes one doublet of microtubules to slide past another doublet. c. Since all microtubule doublets are anchored together at their base, dynein movement causes the entire structure to bend. From textbook Fig. 6.25, p. 116 This illustration shows that movement would occur without bending if the doublets were not all anchored at their bases. This illustration shows the bending that occurs since the doublets are all anchored at their bases. * From textbook Fig. 6.25, p. 116 An elaborate cellular control mechanism regulates exactly which dynein molecules are energized at each interval of time, thereby controlling the direction of bending of the microtubule doublets at each interval of time. Sequential energization of dynein on different microtubule doublets causes the flagellum to bend in different directions at different periods of time. Bending of a microtubule doublet causes the entire flagellum (or cilium) to bend since all of the doublets and other components of the flagellum are anchored together. flagellum (or cilium), showing plasma membrane covering Numbered arrows show different directions of flagellar bending at different periods of time. * The microtubule doublets of each flagellum (or cilium) extend into the cell for a short distance, where they become microtubule triplets, in a structure called a basal body . In cells that contain flagella, separate microtubules or bundles of several microtubules often start at the region of the basal bodies and extend into various regions of the cell. They are called flagellar roots ....
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This note was uploaded on 06/11/2010 for the course BIO 48765 taught by Professor Sathasvian during the Spring '10 term at University of Texas at Austin.

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Lecture 7.Feb3 - BIO 311C Spring 2010 Lecture 7 Wednesday 3...

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