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Essential Cytoskeleton Structures: Function and Maintenance

Explore the vital role of cytoskeleton in maintaining cell shape, organelle anchorage, motility, and regulation. Learn about microtubules, microfilaments, and intermediate filaments, crucial for cellular activities. Understand the evolutionary significance and structural intricacies while delving into cell junctions and intercellular interactions in animal and plant cells.

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Essential Cytoskeleton Structures: Function and Maintenance

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  1. Chapter 7.The Cell: Cytoskeleton AP Biology 2005-2006

  2. Cytoskeleton • Function • structural support • maintains shape of cell • provides anchorage for organelles • motility • cell locomotion • cilia, flagella, etc. • regulation • organizes structures & activities of cell AP Biology 2005-2006

  3. Cytoskeleton • Structure • network of fibers extending throughout cytoplasm • 3 main protein fibers • microtubules • microfilaments • intermediate filaments It’s a matter of size… AP Biology 2005-2006

  4. AP Biology 2005-2006

  5. Evolutionary perspective • Proteins that make up the fibers are very similar in all living things • from bacteria to humans • tubulin (all cells) • actin (eukaryote cells) • Means that they are both ancient and essential for life AP Biology 2005-2006

  6. Microtubules • Structure • thickest fibers • hollow rods about 25nm in diameter • constructed of protein, tubulin • grow or shrink as more tubulin molecules are added or removed AP Biology 2005-2006

  7. Microtubules • Function • structural support & cell movement • move chromosomes during cell division • centrioles • tracks that guide motor proteins carrying organelles to their destination • motor proteins: myosin & dynein • motility • cilia • flagella AP Biology 2005-2006

  8. Centrioles • Cell division • in animal cells, pair of centriolesorganize microtubules guiding chromosomes in cell division AP Biology 2005-2006

  9. Cilia & flagella • Extensions of eukaryotic cytoskeleton • Cilia = numerous & short (hair-like) • Flagella = 1-2/cell & longer (whip-like) • move unicellular & small multicellular organisms by propelling water past them • cilia sweep mucus & debris from lungs • flagellum of sperm cells AP Biology 2005-2006

  10. Cilia • Oar-like movement • alternating power & recovery strokes • generate force perpendicular to cilia’s axis AP Biology 2005-2006

  11. Flagella • undulatory movement • force generated parallel to flagellum’s axis AP Biology 2005-2006

  12. Cilia & Flagella • Structure • remember 9+2! • 9 pairs of microtubules around 2 single microtubules in center • bending of cilia & flagella is driven by motor protein • dynein • requires ATP AP Biology 2005-2006

  13. AP Biology 2005-2006

  14. Microfilaments (actin filaments) • Structure • thinnest class of fibers • solid rods of protein, actin • twisted double chain of actin subunits • about 7nm in diameter • Function • 3-D network inside cell membrane • in muscle cells, actin filaments interact with myosin filaments to create muscle contraction AP Biology 2005-2006

  15. “Let’s go to the video tape!” (play movie here) Microfilaments (actin filaments) • Dynamic process • actin filaments constantly form & dissolve making the cytoplasm liquid or stiff during movement • movement of Amoeba • cytoplasmic streaming in plant cells • speeds distribution of materials AP Biology 2005-2006

  16. Intermediate filaments • Structure • specialized for bearing tension • built from keratin proteins • same protein as hair • intermediate in size 8-12nm • Function • hold “things” in place inside cell • more permanent fixtures of cytoskeleton • reinforce cell shape & fix organelle location • nucleus is held in place by a network of intermediate filaments AP Biology 2005-2006

  17. Summary • Microtubules • thickest • cell structure & cell motility • tubulin • Microfilaments • thinnest • internal movements within cell • actin, myosin • Intermediate filaments • intermediate • more permanent fixtures • keratin • actin • microtubule • nuclei AP Biology 2005-2006

  18. AP Biology 2005-2006

  19. AP Biology 2005-2006

  20. Cell Junctions • Where cells touch each other… AP Biology 2005-2006

  21. Plant cell wall • Structure • cellulose • primary cell wall • secondary cell wall • middle lamella = sticky polysaccharides AP Biology 2005-2006

  22. Intercellular junctions • Plant cells • plasmodesmata • channels allowing cytosol to pass between cells plasmodesmata AP Biology 2005-2006

  23. Animal cell surface • Extracellular matrix • collagen fibers in network of glycoproteins • support • adhesion • movement • regulation AP Biology 2005-2006

  24. Intercellular junctions in animals AP Biology 2005-2006

  25. Intercellular junctions • Animal cells • tight junctions • membranes of adjacent cells fused forming barrier between cells • forces material through cell membrane • gap junctions • communicating junctions • allow cytoplasmic movement between adjacent cells • desmosomes • anchoring junctions • fasten cells together in strong sheets AP Biology 2005-2006

  26. AP Biology 2005-2006

  27. AP Biology 2005-2006

  28. A cell is a living unit greater than the sum of its parts AP Biology 2005-2006

  29. And now for some… Stupid Penguin Tricks…. Any Questions?? AP Biology 2005-2006

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