Cell Wall, Structure, Chemical Composition and Functions

CELL WALL

 

Definition:

The outer rigid protective layer of plants , bacteria and fungal cells is called cell wall.

Occurrence:

present in plants , bacteria and fungi.

Chemical composition:-

it composed of cellulose in plants. In bacteria it composed of murein (peptidoglycan), while in fungi it is composed of chitin.

Structure:

Cell walls consist of 3 types of layers

Middle lamella:

This is the first layer formed during cell division. It makes up the outer wall of the cell and is shared by adjacent cells. It is composed of pectic compounds and protein.

Primary wall:

This is formed after the middle lamella and consists of a rigid skeleton of cellulose microfibrils embedded in a gel-like matrix composed of pectic compounds, hemicellulose, and glycoproteins.

Secondary wall:

formed after cell enlargement is completed. The secondary wall is extremely rigid and provides compression strength. It is made of cellulose, hemicellulose and lignin. The secondary wall is often layered.

 

Functions;-

*Thick walled cells provide mechanical support

  • Tubes for long-distance transport
  • Cutinized walls prevent water loss
  • Provide mechanical protection from insects & pathogens
  • Give specific shape to cell.

 

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