Occurrence, structure and functions of heteroglycans-bacterial cell wall polysaccharides, glycosaminoglycans, agar, alginic acid, pectins, amino sugars and deoxy sugars

Heteroglycans, also known as heteropolysaccharides, are complex carbohydrates composed of different types of monosaccharides. They play crucial roles in various biological functions and are found in a variety of organisms. Here’s an overview of their occurrence, structure, and functions, focusing on bacterial cell wall polysaccharides, glycosaminoglycans, agar, alginic acid, pectins, amino sugars, and deoxy sugars:

1. Bacterial Cell Wall Polysaccharides

  • Occurrence: Found in the cell walls of bacteria.
  • Structure: Consist of repeating units of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM) in peptidoglycan.
  • Functions: Provide structural support, maintain cell shape, protect against osmotic pressure, and play a role in cell division.

2. Glycosaminoglycans (GAGs)

  • Occurrence: Found in animal tissues, particularly in connective tissues.
  • Structure: Long, unbranched polysaccharides composed of repeating disaccharide units, typically containing an amino sugar (such as glucosamine or galactosamine) and a uronic acid.
  • Functions: Provide structural integrity, lubricate joints, and participate in cell signaling and repair.

3. Agar

  • Occurrence: Derived from red algae (Rhodophyta).
  • Structure: A mixture of agarose and agaropectin; agarose is a linear polymer of agarobiose (a repeating unit of galactose and anhydrogalactose).
  • Functions: Used as a gelling agent in microbiological media, food industry, and pharmaceuticals.

4. Alginic Acid

  • Occurrence: Found in brown algae (Phaeophyceae).
  • Structure: Composed of β-D-mannuronic acid and α-L-guluronic acid residues.
  • Functions: Used as a thickening, gelling, and stabilizing agent in food and industrial applications; also used in wound dressings and drug delivery systems.

5. Pectins

  • Occurrence: Found in the cell walls of plants, particularly in fruits.
  • Structure: Complex polysaccharides rich in galacturonic acid; may also contain rhamnose, arabinose, and galactose.
  • Functions: Provide structural integrity to plant cells, aid in plant growth, and are used as gelling agents in food products like jams and jellies.

6. Amino Sugars

  • Occurrence: Found in various biological molecules, including glycoproteins, glycolipids, and bacterial cell walls.
  • Structure: Monosaccharides in which a hydroxyl group is replaced by an amino group (e.g., glucosamine, galactosamine).
  • Functions: Play roles in cellular communication, structural integrity, and the formation of glycosaminoglycans and other biomolecules.

7. Deoxy Sugars

  • Occurrence: Present in DNA (deoxyribonucleic acid) and various natural products.
  • Structure: Sugars in which a hydroxyl group is replaced by a hydrogen atom (e.g., deoxyribose in DNA).
  • Functions: Integral components of nucleic acids, contribute to the structural diversity of natural products, and play roles in cell signaling and metabolic pathways.

These heteroglycans are essential for various structural and functional roles in both prokaryotic and eukaryotic organisms. They are involved in maintaining the integrity of cell walls, providing mechanical strength, facilitating cell-cell communication, and participating in numerous biochemical processes.

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