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Cell Cytoskeleton



  • provides structural support to the cell and determines its shape.

  • is a network of fibrillar proteins.

  • These fibrilar proteins are synthesized by polymerization of precursor molecules → if not needed anymore → disassemble → reassemble where and where needed → thus the cytoskeleton can be dynamic as needed.

  • Components:

    • Microtubules

    • Filaments

      • Thin filaments

      • Thick filaments

      • Intermediate filament

Microtubules

  • polymer of tubulin.

  • have a hollow lumen at the center.

  • 20-30 nm in diameter.

Functions
  • Form and move structures like:

    • Cilia

    • Flagella

    • Centrioles

    • Mitotic spindle

  • Form a track for intracellular organelles to move from one area of the cell to the other

Thin & Thick Filaments

  • Thin filaments are made up of actin

  • Thick filaments are made up of myosin

Functions: They play role in...
  • Muscle contraction

  • Cell movement e.g. gliding, cytokinesis

  • Extend process from cell e.g.

    • Formation of axon in neuron

    • Formation of microvilli in epithelial cells

Intermediate Filaments

  • There is a large variety of subunit proteins that can form intermediate filaments.

  • Expression of different subunits in different cells results in formation of different intermediate filaments in different cells. For example:

    • Epithelial cells have keratins

    • Nerve cells have neurofilaments

    • Muscle cells have desmin

Functions
  • Radiate from the cell area subject to tensile stress → Reinforce such area against tensile stress.

  • In epithelial cells, they insert at the desmosomal junctions that attach neighboring cells to one another.

 

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