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STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
STPM Form 6 Biology Cytoskeleton
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STPM Form 6 Biology Cytoskeleton

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STPM Form 6 Biology Cytoskeleton

STPM Form 6 Biology Cytoskeleton

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  • 1. Cytoskeleton
  • 2. Cytoskeleton Means “cell skeleton” Internal framework of cell Has many functions  Anchoring cell organelles  Provide cell shape  Aids in cell motility  Response to environmental signals Comprises  Microtubules  Microfilaments  Intermediate filaments
  • 3. Made of proteins Dynamic properties Coordinate with each otherCoordinate with external signal
  • 4. The cytoskeleton is composed ofnetworks of 3 different filaments
  • 5. The cytoskeleton is dynamic
  • 6. Microtubules Hollow tubes made of the protein tubulin  Alternating dimers of and tubulin Largest of cytoskeleton filaments Is used for:  Maintenance of cell shape  Motility  Flagella or cilia  Movement of organelles through cell  Often involves motor molecule  Often originate from centrosome  Spindle Fibres formation  Cell wall formation  Mechanical Support
  • 7. Table 6-1a 10 µm Column of tubulin dimers 25 nm Tubulin dimer
  • 8. Microtubules are organized toperform specific functions
  • 9. Maintain Cell Shape
  • 10. Holding Organelles in Place
  • 11. Mechanical Support
  • 12. Microtubule structure
  • 13. The centrosome is the primarymicrotubule nucleation site inmost cells
  • 14. Centrosome Microtubules Organizing Centre Hold centrioles
  • 15. Location of Centrosome
  • 16. Centrosomes act to polarize themicrotubule network Plus end - fast growing, usually in the cytoplasm Minus end - slow growing, anchored at the centrosome in most cells
  • 17. Centrioles  Located in centrosome of animal cells  Occur in perpedicular pair  Have 9 triplets of microtubules  Facilitate microtubule assembly and chromosome separation in some cells  Divide during cell division
  • 18. Fig. 6-22 Centrosome Microtubule Centrioles 0.25 µm Longitudinal section Microtubules Cross section of one centriole of the other centriole
  • 19. Flagellum structure Basal body links flagellum or cilia to cell surface  Basal body looks just like a centriole 9 +2 arrangement of microtubules (eukaryotes) 9+0 arrangement of microtubules (prokaryotes) Radial spokes prevent dramatic sliding and only bending
  • 20. Microtubule Organization ofFlagella
  • 21. Movement of Cillia and Flagella
  • 22. Fig. 6-24 Outer microtubule 0.1 µm Plasma doublet membrane Dynein proteins Central microtubule Radial spoke Protein cross- Microtubules linking outer doublets (b) Cross section of Plasma cilium membrane Basal body 0.5 µm (a) Longitudinal 0.1 µm section of cilium Triplet (c) Cross section of basal body
  • 23. Basal Body
  • 24. Structure  Microtubules  Alpha & Beta Tubulin  Microfilament  Actin molecules
  • 25. Cell motility Cell movement facilitated by flagella or cilia Unlike in prokaryotes, eukaryotic flagella undulate Cilia are small appendages and they move like a swimmers arm-active stroke and return stroke
  • 26. Fig. 6-25 Microtubule doublets ATP Dynein protein (a) Effect of unrestrained dynein movement ATP Cross-linking proteins inside outer doublets Anchorage in cell (b) Effect of cross-linking proteins 1 3 2 (c) Wavelike motion
  • 27. Microfilaments Made of two intertwined strands of actin Helps maintain cell shape  Actin rearrangements allow engulfment events  Psuedopod formation in ameoba Promote cytoplasmic streaming in plants Essential for muscle contraction Used by invading bacteria to move around cell Frequently being assembled and disassembled within cell Cytokinesis
  • 28. Table 6-1b 10 µm Actin subunit 7 nm
  • 29. Microfilaments 2  Myosin interacts with actin to cause contraction  Cytoplasmic streaming and ameoboid motion are similar  Cortical cytoplasm around the perimiter of cell contains perpendicular actin (wind fence)  Streaming portion has parallel actin which facilitates cytoplasm movement  Plant cell wall prevents amoeboid movement of plant cell
  • 30. Intermediate Filaments Resemble cable in structure Are made of protein subunits Help maintain cell shape Are durable and not assembled and disassembled as other cytoskeleton components May help maintain organelle position
  • 31. Table 6-1c 5 µm Keratin proteins Fibrous subunit (keratins coiled together) 8–12 nm

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