in Cell Structure and Function by

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The cytoskeleton is made up of:

1. Microtubules:

  1. It is a cylindrical tube measuring 20-25 nm in diameter.
  2. It is composed of sub-units of protein tubulin (α and β sub-units)


  • It determines the cell shape.
  • Formation of spindle fibres during mitosis.
  • Conduction of nerve impulses.
  • Cilia and flagella movement..

2. Microfilaments:

  1. These are fine thread-like protein fibres, made up of contractile protein – actin.
  2. They measure about 50Ao in diameter.


  • Mechanical support.
  • In the muscle cells, they help in movement and locomotion.
  • In microvilli, they help in absorption.

3. Intermediate filaments:

  1. They are ultramicroscopic structures present in the cytoplasm or in between the cells.
  2. Tough unbranched protein fibres measuring about 10 nm in diameter.


  • Impart structural stability to the cell.
  • Mechanical (tensile) strength to the cell.
  • Example: Keratin.
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