Cell Wall Structure and Function | Free Biology Notes

Cell Wall Structure and Function

In this article we will discuss about:- What is cell wall?, Characteristics of Cell Wall, Cell Wall Structure, What is Pits and its types and Functions of cell wall

What is Cell Wall?

  • Cell wall is rigid and protective layer around the plasma membrane
  • Discovered by Robert hooke in 1665
  • Cell wall non-living rigid structure
  • Found in plants, fungi, prokaryotes and protists
  • Composition of cell wall varies in different groups

Characteristics of Cell Wall

  • Cell wall is a rigid and protective layer around the plasma membrane
  • It is a non-living structure
  • Animal cells do not have a cell wall
  • Found in in most plant cells, fungi, bacteria, algae, and some archaea
  • Cell wall has many important functions in a cell including protection, structure, and support

Cell Wall Structure

Structure of Prokaryotes Cell Wall

  • Cell wall is made up of peptidoglycon
  • peptidoglycan made up of polysaccharide chains cross-linked by unusual peptides containing D-amino acids
  • A notable difference between the cell walls of gram-positive and gram-negative bacteria is the substantially thicker peptidoglycan layer in gram-positive bacteria.
  • Cell wall of gram-positive bacteria contains teichoic acids

Structure of Fungi Cell Wall

  • Fungal cell wall is made up of three main components


  • Polymers consisting mainly of unbranched chains of β-(1,4)-linked-N-Acetylglucosamine in the Ascomycota and Basidiomycota, or poly-β-(1,4)-linked-N-Acetylglucosamine (chitosan) in the Zygomycota
  • Both chitin and chitosan are synthesized and extruded at the plasma membrane


  • Glucose polymers that function to cross-link chitin or chitosan polymers
  • β-glucans are glucose molecules linked via β-(1,3)- or β-(1,6)- bonds and provide rigidity to the cell wall while α-glucans are defined by α-(1,3)- and/or α-(1,4) bonds and function as part of the matrix


  • Enzymes necessary for cell wall synthesis and lysis in addition to structural proteins are all present in the cell wall.
  • Most of the structural proteins found in the cell wall are glycosylated and contain mannose, thus these proteins are called mannoproteins or mannans.

Structure of Plant cell wall

  • Cell wall is made up of 4 layers
  • Middle lamella, primary, secondary and tertiary wall

I) Middle lamella

  • Cementing layer between the cells
  • It is made up of ca & mg pectates

II) Primary cell wall

  • Found in growing cell
  • It has high hemicelluloses & less cellulose content

III) Secondary cell wall

IV) Tertiary cell wall

  • Laid down on secondary wall
  • Found in tracheids of gymnosperms

What is Pits?

  • Cell wall is not uniform in thickness throughout
  • Certain places cell wall are not laid down, such places are called pits

Pits are of two types

I) Simple Pit

  • Pit chamber is uniform in diameter
  • Found in angiosperms

II) Bordered pit

  • Pit chamber is flask shaped
  • Found in gymnosperms
  • Number of plasmodesmata or cytoplasmic strands are present in pit

 Functions of cell wall

  • Maintains shape of the cells
  • Protects cell from mechanical injury
  • Allows materials to pass in and out of the cell
  • Prevents undue expansion of cell when water enters by osmosis

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