Disaccharides, Biology


  • They are oligosaccharides composed of two monosaccharide residues .
  • Three common disaccharides are   sucrose (glucose + fructose) = cane suger maltose (glucose + glucose) = malt sugar lactose (glucose + galactose) = milk sugar
  • Common formula is Cn(H2O)n-1.


  • Commercial or Table sugar.
  • Obtained from stems of Sugarcane (Saccharum officinarum) and roots of Beet sugar (Beta vulgaris).
  • Sucrose is a non-reducing sugar.
  • Sweetness index of sucrose is 100.
  • Formed of two molecules each of glucose and fructose.
  • It has neither aldehyde group nor keto group.


  • Malt Sugar
  • It is a disaccharide formed of two molecules of glucose which are connected to each other through the a -1, 4 D-glycosidic linkage.
  • It is present in Barley.
  • Maltose is formed during hydrolysis of starch.
  • It is found in germinating cereals.
  • The sugar is present in malt, and is therefore, also called malt sugar.
  • Sweetness index is 30.
  • Maltose is a reducing surgar.


  • Milk Sugar.
  • It is a disaccharide sugar present in milk upto the extent of 5%.
  • Lactose is formed of D-galactose and D-glucose, both in pyranose state, through the b-1, 4 glycocydic bond.
  • The monosaccharide galactose is also synthesised from glucose inside the mammary glands.
  • Sweetness index of lactose is 16.
  • Like maltose, lactose is a reducing sugar.
  • Souring of milk occurs when bacteria convert lactose into lactic acid.
  • Present only in mammals.


  • It is a disaccharide sugar made of two glucose residues which was originally obtained from cocoon of Trehela (weevil Larinus species) as sweetening agent.
  • Trehalose is found in haemolymph of some insects and fungi including yeast.
Posted Date: 10/9/2012 3:37:03 AM | Location : United States

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