The Cytoskeleton

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overview of cellular cytoskeleton

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The Cytoskeleton

  1. 1. Cellular Structural Support
  2. 2. <ul><li>a network of fibers extending throughout the cytoplasm </li></ul>Cytoskeleton
  3. 3. <ul><li>a network of fibers extending throughout the cytoplasm </li></ul>Cytoskeleton microtubules
  4. 4. <ul><li>a network of fibers extending throughout the cytoplasm </li></ul>Cytoskeleton microtubules intermediate filaments
  5. 5. <ul><li>a network of fibers extending throughout the cytoplasm </li></ul>Cytoskeleton microtubules intermediate filaments microfilaments
  6. 6. <ul><li>maintains shape of the cell. </li></ul>Some functions:
  7. 7. <ul><li>maintains shape of the cell. </li></ul><ul><li>provides anchorage for organelles and cytosolic enzymes </li></ul>Some functions:
  8. 8. <ul><li>maintains shape of the cell. </li></ul><ul><li>provides anchorage for organelles and cytosolic enzymes </li></ul><ul><li>provides tracks for movement of organelles </li></ul>Some functions:
  9. 9. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  10. 10. <ul><li>cilia & flagella </li></ul><ul><li>centrioles </li></ul>Microtubules
  11. 11. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 7.22 In animal cells, the centrosome has a pair of centrioles , consisting of microtubules arranged in a ring. During cell division the centrioles replicate.
  12. 12. <ul><li>Microtubules are the central structural supports in cilia and flagella . </li></ul>Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 7.2
  13. 13. <ul><li>A flagellum has an undulatory movement </li></ul>Fig. 7.23a
  14. 14. <ul><li>Cilia move more like oars </li></ul>
  15. 15. <ul><li>In spite of their differences, both cilia and flagella have the same ultrastructure. </li></ul><ul><ul><li>Both have a core of microtubules sheathed by the plasma membrane. </li></ul></ul>
  16. 16. <ul><li>The bending of cilia and flagella is driven by the arms of a motor protein, dynein . </li></ul><ul><ul><li>Addition to dynein of a phosphate group from ATP and its removal causes conformation changes in the protein. </li></ul></ul><ul><ul><li>Dynein arms alternately grab, move, and release the outer microtubules. </li></ul></ul><ul><ul><li>Protein cross-links limit sliding and the force is expressed as bending. </li></ul></ul>Fig. 7.25
  17. 17. <ul><li>solid rods of protein called actin used in: </li></ul>Microfilaments Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  18. 18. <ul><li>solid rods of protein called actin used in: </li></ul>Microfilaments Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings muscle cell contraction
  19. 19. <ul><li>solid rods of protein called actin used in: </li></ul>Microfilaments Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings muscle cell contraction extension of pseudopodia
  20. 20. <ul><li>solid rods of protein called actin used in: </li></ul>Microfilaments Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings muscle cell contraction extension of pseudopodia cytoplasmic streaming
  21. 21. <ul><ul><li>Myosin molecules walk along the actin filament, pulling stacks of actin fibers together and shortening the cell. </li></ul></ul>
  22. 22. <ul><li>In other cells, these actin-myosin aggregates are less organized but still cause localized contraction. </li></ul><ul><ul><li>A contracting belt of microfilaments divides the cytoplasm of animal cells during cell division. </li></ul></ul><ul><ul><li>Localized contraction also drives amoeboid movement. </li></ul></ul><ul><ul><ul><li>Pseudopodia , cellular extensions, extend and contract through the reversible assembly and contraction of actin subunits into microfilaments. </li></ul></ul></ul>Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 7.21b
  23. 23. <ul><li>In plant cells actin-myosin interactions drive cytoplasmic streaming . </li></ul><ul><ul><li>This creates a circular flow of cytoplasm in the cell. </li></ul></ul><ul><ul><li>This speeds the distribution of materials within the cell. </li></ul></ul>

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