Carbohydrates (Biology)

  • Carbohydrates [Cn H2n On] are sugars with H:O as 2:1 also with a terminal aldehyde and they are of three types (i) Monosaccharides (ii) Oligosaccharides (iii) Polysaccharides.
  • Monosaccharides contain a single unit of sugar and cannot be hydrolysed still and based on the carbon it possesses, it can be of different types of such as triose, tetrose, pentose, hexose etc., Eg [Glyceraldehyde, Ribose, Ribulose, Glucose, Galactose, Mannose].
  • Oligo saccharides are of three types (i) Disaccharide (ii) Tri & (iiI) Tetrasaccharides.
  • 2 units of sugar comprise disaccharide Eg. Sucrose (cane sugar) – non reducing sugar [Glucose + Fructose (1→2 linkages)] ; Lactose (milk sugar) – reducing sugar (Glu + Galactose).
  • Trisaccharide (Eg. Raffinose = Glu + Gal + Fructose ; present in fungi)
  • Tetrasaccharide (Eg. Stachylose = Glu + 2 Gal + Fru; present in Stachys tubifera)
  • Oligosaccharides contain 2-9 units of sugar molecules
  • Polysaccharides comprise more than 10 sugar units and they are not sweet.
  • The linear form of glucose exits as IMAGE
  • Ring/chair form occurs in pyranose (hexagon) and furanose (pentagon).
  • 2 units of glucose combines with the glycosidic bond to form maltose (or) maltobiose (or) α-D-glucopyranosyl (1 → 4) α-D gluco pyranose.
  • Cellobiose is β-D-gluco pyranosyl (1-4) β-D-gluco pyranose.
  • Glucose is blood sugar and Fructose is fruit sugar [Exception : grape]
  • Reducing sugar reduces cupric ions to cuprous form [Eg: reduction of Fehling’s (or) Benedict’s Solution]. All sugars which possess free aldehyde (or) ketone are reducing sugars.
  • Homo and Heteropolysaccharides are the two types of polysaccharides.
  • Examples of Homo polysaccharides are cellulose, starch (Amyose α1→4, Amylopectin α1→1) glycogen, chitin, Inulin (Found in Dahlia), Dextrin.
  • Examples of Hetero polysaccharide are Hyaluronic acid (animal cement), Chondroitin, Heparin, pectin (plant cement), Hemicellulose.

View this video for the topic Carbohydrates from 15:56 to 55:03

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