Oligosaccharides

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Oligosaccharides

  1. 1. CHEMISTRY OF CARBOHYDRATES- 2 •OLIGOSACCHARIDES POLYSACCHARIDES DR.RITTU CHANDEL 04-09-12
  2. 2. CARBOHYDRATE MONOSACCHARI DE OLIGOSACCHARI DE Two to ten monosaccharide units on hydrolysis HOMOPOLYSACCHARID E POLYSACCHARI DE More than ten monosaccharide units on hydrolysis HETEROPOLYSACCHA RIDE
  3. 3. DISACCHARIDES • • • Most common among oligosaccharides two monosaccharide units (similar or dissimilar) held by glycosidic bonds properties – water soluble, sweet to taste REDUCING NON REDUCING MALTOSE,LACTOSE,ISOMALTOSE,CELLOBI SUCROSE,TREHAL OSE
  4. 4. DISACCHARIDES CONSTITUENTS REDUCING (+)- MALTOSE GLUCOSE+GLUCOSE (+)- LACTOSE GLUCOSE+GALACTOSE (+)-CELLOBIOSE GLUCOSE+GLUCOSE MELIBIOSE NON REDUCING (+)-SUCROSE TREHALOSE GLUCOSE+GALACTOSE GLUCOSE+FRUCTOSE GLUCOSE+GLUCOSE
  5. 5. MALTOSE (malt sugar)
  6. 6. MALTOSE • • • •     Digestion of starch by amylase,germinating seeds, malt Action of maltase or dilute acid on maltose gives glucose units Fermented by yeasts PROPERTIES: Reducing sugar, soluble and sweet taste Sunflower shaped osazones Mutarotation Exhaustive methylation of all free –OH group,followed by hydrolysis of glycosidic linkage gives 2,3,4,6-tetra-O-methyl-D-glucose and 2,3,6-triO-methyl-D-glucose
  7. 7. LACTOSE (MILK SUGAR)
  8. 8. LACTOSE • • •      In milk Action of intestinal lactase on lactose gives glucose and galactose PROPERTIES: Reducing sugar Powder puff or hedgehog or badminton ball shaped osazone Not very soluble and not so sweet dextrorotatory At body temperature exists as an equilibrium mixture of α and β forms in 2:3
  9. 9. LACTOSE • • Fearon’s test lactosuria
  10. 10. SUCROSE (TABLE SUGAR)
  11. 11. SUCROSE • • • • • In sugar cane,sugar beet,pineapple,carrot roots Major carbohydrate in photosynthesis (in roots,tuber,seeds) Most abundant among naturally occuring sugars Distinct advantage:storage and transport forms Action of Intestinal sucrase on sucrose gives glucose and fructose
  12. 12. SUCROSE PROPERTIES  Non reducing  No osazone formation  Very soluble and very sweet  Specific sucrose test  USE  Sweetening agent in food industry 
  13. 13. INVERSION OF SUCROSE • • • • • Dextrotatory sucrose (+66.5˚) on hydrolysis becomes levorotatory Equimolar mixture of glucose and fructose is invert sugar Honey contains invert sugar (sweeter than sucrose) β-D-glucopyranose α -D-glucopyranose +18.7 ˚ +112.2 ˚ Sucrose sucrase β -D-fructofuranose β -D-fructopyranose -133 ˚ α -D-fructopyranose -21˚
  14. 14. ISOMALTOSE, GENTIOBIOSE ISOMALTOSE - Glucose + glucose α(1 → 6) partial hydrolysis of glycogen and starch gives it oligo-1,6-glucosidase in intestinal juice hydrolyses GENTIBIOSE - β (1 → 6) glucose +glucose
  15. 15. TREHALOSE Non reducing sugar Distinctive sweet taste Major sugar of insect endolymph
  16. 16. CELLOBIOSE 6 CH 2OH H 4 OH 5 6 O H OH H 5 H 1 O CH 2OH 4 O H OH H 3 H 2 OH 3 cellobiose H H 2 OH 1 H OH Virtually no taste Not fermented by yeast Obtained by hydrolysis of cellulose Indigestible by humans Β(1→ 4) linkage is represented as zigzag but one glucose is actually flipped over relative to other
  17. 17. LACTULOSE A ketodisaccharide • Fermented by intestinal bacteria • Used in osmotic laxative, in hepatic encephalopathy α-D-galactopyranosyl-(1 → 4)-β-Dfructofuranose •
  18. 18. TRISACCHARIDES • RAFFINOSE in sugar beets • O-α-D-galactopyranosyl-(1→6)-0-α-D- glucopyranosyl (1→2)-β-D-fructofuranoside • MELEZITOSE in sap of some coniferous trees O-α-D-glucopyranosyl-(1→3)-O-β-D-fructofuranosyl-(2 → 1)-α-Dglucopyranoside
  19. 19. TETRASACCHARIDE STACHYOSE  Galactose+galactose+glucose+fructose  PENTASACCHARIDE  VERBASCOSE   Galactose+Galactose+galactose+glucose+fructose
  20. 20. POLYSACCHARIDES(GLYCANS) Repeat units of monosaccharides or their derivatives,held by glycosidic bonds Relatively or totally insoluble,tasteless LINEAR BRANCHED
  21. 21. POLYSACCHARIDES HETEROPOLYSACCHA RIDE HOMOPOLYSACCHAR IDE GLUCA N FRUCTOS AN MANNANS
  22. 22. HOMOPOLYSACCHARID E STORAGE POLYSACCHARIDE STARCH GLYCOGEN DEXTRANS INULIN STRUCTURAL POLYSACCHARIDE CHITIN CELLULOSE
  23. 23. STARCH
  24. 24. STARCH • • • • • Most important dietary source of man and animals Carbohydrate reserve of plants In potato,tapioca,rice,wheat Deposited in form of granules in cytoplasm STARCH Acid hydrolysis GLUCOSE
  25. 25. AMYLOSE Amylose α(1 → 4) Not soluble in water Forms hydrated micelles Gives blue colour with iodine Helical coil with 6 glucose/turn Amylopectin α(1→4) but branching points are α(1→ 6) Most abundant in plants Gives red violet colour with iodine
  26. 26. AMYLASES Two types-α and β Both hydrolyse only α- glycosidic bonds α- amylase = α(1→4)-glucan-4glucanhydrolase β-amylase = α(1→4)-glucan-4-maltohydrolase Debranching enzyme- α (1→6)-glucosidase or α (1→6)- glucan-6-glucanhydrolase
  27. 27. BREAKDOWN PRODUCTS OF STARCH STARCH AMYLOPECTIN BLUE VIOLET ERYTHRODEXTRIN RED ACHRODEXTRIN NO MALTOSE NO
  28. 28. GLYCOGEN Main storage polysaccharide of animal cell Abundant in liver and skeletal muscle Also in plants that do not have chlorophyll Animal starch Immediate source of energy Dextrorotatory Not readily soluble in water and forms opalascent solution Not destroyed by hot strong KOH or NaOH With iodine gives deep red colour
  29. 29. GLYCOGEN Glycogen is used as energy source,glucose units are removed one at a time from non reducing ends Glucose is not stored in monomeric form Starch and glycogen are heavily hydrated
  30. 30. DEXTRAN        Polymer of D-glucose Synthesized by leuconostoc mesenterides Dental plaque Synthetic dextrans Branched polysaccharide of D-glucose Branching at 1 → 2, 1 → 3, 1 → 4 or 1 → 6 Plasma volume expander
  31. 31. INULIN D-fructose residues in β(2→1) In dahlia,garlic,onion,dandelion White, tasteless powder Levorotatory No dietary importance in humans Used for estimation of body water volume(ECF),assesing kidney functions through means of GFR
  32. 32. CHITIN Second most abundant polysaccharide
  33. 33. CELLULOSE Not attacked by α or β amylase
  34. 34. CELLULOSE Schematic of arrangement of cellulose chains in a microfibril. Every other glucose molecule is flipped over other due to β linkages Parallel orientation is favoured by intermolecular hydrogen bond X-ray diffraction of cellulose shows bundles of parallel chains to form fibrils Not digested by mammals
  35. 35. CELLULOSE Most abundant structural polysaccharide in plants Cotton fibers are pure cellulose Insoluble in water Complete hydrolysis D-glucose Strong acids CELLULOSE partial hydrolysis Cellobiose Exhaustive methylation 2,3,6-tri-O-methyl glucose
  36. 36. BIBLOGRAPHY LEHNINGER HARPER TALWAR BHAGVAN DEBJYOTI DAS
  37. 37. THANK YOU

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