Centrosomes and Centrioles

  • Centrioles are non – membranous cylindrical bodies found near the nucleus in the¬†centrosome, a granular mass that serves as an organizing center for microtubules.
  • These are seen in animal cells and flagellated plant cells.
  • Centriole can be viewed only during cell division.

  • Centrosome usually contains two centrioles.
  • A pair of centrioles is called diplosome.
  • They are positioned at right angles to each other.
  • Each centriole is made of nine bundles of microtubules (three per bundle) arranged in a ring.
  • The fibres of centrioles contain tubulin, along with Lipid molecules.
  • The triplet fibres are connected together by a dense material.

Functions

  • These are the centres for the organisation of spindle fibres in animal cells.
  • These become the basal bodies of cilia and flagella
  • These are responsible for the development of cilia and flagella.

Microbodies

These are small spherical, subcellular organelles bounded by a unit membrane containing enzymes like oxidase, peroxidase and catalase. They were first described by Rhodin in 1954.

  • Microbodies arise from ER by budding.
  • They are found in close association with ER, mitochondria and chloroplast.

The microbodies are of two types.

Glyoxysomes:

  • These are small cell organelles containing the enzymes of the glyoxylate cycle.
  • These are found in plant cells and are particularly abundant in germinating seeds.
  • Glyoxysomes also contain the enzymes for oxidation of alcohols and alkane.

Peroxisomes:

  • These are microbodies containing peroxidase enzymes.
  • They are involved in the formation and decomposition of hydrogen peroxide.
  • They also involve in -oxidation of fatty acids.
  • They also serve as the sites of photorespiration.

 

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