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Main Functions of Cell Wall

In the cells of bacteria, cyanobacteria, protists, fungi and plants, a thick rigid, protective but porous coat, the cell wall, outside the plasma membrane is found.  One of the most important differences between plant and animals  is the presence of cell wall in plant cells. The composition of cell wall varies in different groups.
  • In plants, cell wall is made up of cellulose, hemicellulose and pectin.
  • In fungi, cell wall is made up of Chitin.
  • In bacteria, cell wall composed of protein-lipid-polysaccharides having two components: NAG (N acetyl glucosamine) and NAM (N acetyl muramic acid)
A typical plant cell wall is made up of four layers: middle lamella, primary, secondary and tertiary wall.
Plant Cell Wall
Functions of Cell wall
  • Cell wall provides shape to plant cells.
  • It imparts rigidity to cells
  • Cell wall functions as a barrier to the entry of pathogens(viruses, bacteria, fungi and protozoans) into the cells.
  • It provides protection to protoplasm against mechanical injury.
  • Cell wall  cannot entry or exit of materials from the cells.
  • Cell walls function as apoplast which is permeable to water and minerals dissolved in it.
  • Plasmodesmata or cytoplasmic bridges between adjacent cells produce a protoplasmic continuum called symplast. Symplast is useful in synchronisation of cellular activates.
  • Growth of the cell wall enables the cells to enlarge in size.
  • Cell wall develop mechanical support for the plant to withstand gravitational forces.
  • Cell growth is made possible only when the cell wall undergoes extension.
  • It counteracts osmotic pressure.
  • Cell wall prevents bursting of cells on endosmosis.
  • Turgor pressure, counter balanced by wall pressure, provides support to delicate organs like leaves and flowers.
  • Suberin deposited on endodermal walls (casparian strips) make the root endodermis a biological check post.
  • Silica, other minerals and organic deposits present on the walls of surface cells of grasses and other plants protects them from fungal attack and herbivores.
  • Cutin, wax and suberin protect the plant surface from excessive transpiration loss of water in vapour form.
  • Sieve pores present in the transverse walls of sieve elements help in long distance passage of food materials.
  • Walls of tracheids and vessels are specialized to allow long distance transport of sap.
  • Cellulose, hemicelulose and pectins present in the walls are commercially exploited.
  • The wall in some cases has  a role in defence and offence by means of spines.

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