Cell Wall: Structure and Function complete notes simple and easy.

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 What is Cell wall?

Some organisms like plants and fungi have an outer layer around cells called as Cell Wall. The composition of cell wall varies in plants and fungi.

  • All plants have cell wall except some.
  • Cell wall provides protection to the protoplasm.
  • The cell wall surrounds the plasma membrane of plant cells and provides tensile strength and protection against mechanical and osmotic stress.
  • Cell wall of fungi is made up of Chitin a Polysaccharide.
  • In Plants, structurally it is mainly composed of Cellulose, Hemicellulose and Pectic substance.
  • These three substances are Polysaccharides in nature.
  • The main constituent of cell wall is cellulose.
PLANT CELL WALL
  • The main constituent of cell wall is Cellulose.
  • Cellulose is a polymer of beta-D-Glucose, each monomer joined together by beta 1-4 linkage of glycosidic bond.
  • Once the polysaccharide Cellulose lie adjacent to each other they start forming microfibrils.
  • Adjacent cellulose packed together parallelly to form cellulose microfibrils.
  • The polymer of cellulose grows at one end with help of complex of enzymes that add new glucose residue once at a time.
  • These enzymes are intrinsic membrane proteins named as cellulose synthase
  • Cellulose in microfibrils are not able to link together so they link together with help of Matrix material.
  • Matrix material are produced in dictyosome and brought to cell wall via vesicles that fuses with Plasma Membrane.
  • Matrix material includes Hemicellulose and Pectic polysaccharides.
  • Microfibrills has great strength but it get increased by matrix.
  • Cellulose microfibrils link together with each other with help of another polysaccharide HemiCellulose, it forms hydrogen bonding with cellulose called as HemiCellulose.
  • In multicellular plants wall of one cell is attached to adjacent cell by an ADHESION layer composed of Pectic substance (Galactouronans) called as MIDDLE LAMELLA.
STRUCTURE

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