oligosaccharides
TRANSCRIPT
•OLIGOSACCHARIDES POLYSACCHARIDES
CHEMISTRY OF CARBOHYDRATES- 2
DR.RITTU CHANDEL 04-09-12
CARBOHYDRATE
MONOSACCHARIDE
OLIGOSACCHARIDE
POLYSACCHARIDE
Two to ten monosaccharide units on hydrolysis
More than ten monosaccharide units on hydrolysis
HOMOPOLYSACCHARIDE
HETEROPOLYSACCHARIDE
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,CELLOBIOSE
SUCROSE,TREHALOSE
DISACCHARIDES CONSTITUENTS
REDUCING
(+)- MALTOSE GLUCOSE+GLUCOSE(+)- LACTOSE GLUCOSE+GALACTOSE (+)-CELLOBIOSE GLUCOSE+GLUCOSE MELIBIOSE GLUCOSE+GALACTOSE
NON REDUCING(+)-SUCROSE GLUCOSE+FRUCTOSE
TREHALOSE GLUCOSE+GLUCOSE
-
MALTOSE (malt sugar)
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-tri-O-methyl-D-glucose
LACTOSE (MILK SUGAR)
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
LACTOSE
• Fearon’s test• lactosuria
SUCROSE (TABLE SUGAR)
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
SUCROSE
PROPERTIES Non reducing No osazone formation Very soluble and very sweet Specific sucrose test USE Sweetening agent in food industry
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)
• Sucrose•
sucraseα -D-glucopyranose+112.2 ˚
β-D-glucopyranose+18.7 ˚
β -D-fructofuranose β -D-fructopyranose-133 ˚
α -D-fructopyranose-21˚
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
TREHALOSE
Non reducing sugarDistinctive sweet tasteMajor sugar of insect endolymph
CELLOBIOSE
Virtually no tasteNot fermented by yeastObtained by hydrolysis of celluloseIndigestible by humansΒ(1→ 4) linkage is represented as zigzag but one
glucose is actually flipped over relative to other
H O
OH
H
OHH
OH
CH 2OH
H
O OH
H
H
OHH
OH
CH 2OH
H
H
H
O1
23
4
5
6
1
23
4
5
6
cellobiose
LACTULOSE
• A ketodisaccharide• Fermented by intestinal bacteria• Used in osmotic laxative, in hepatic
encephalopathyα-D-galactopyranosyl-(1 → 4)-β-D-
fructofuranose
TRISACCHARIDES
• RAFFINOSE in sugar beets• O-α-D-galactopyranosyl-(1→6)-0-α-D- glucopyranosyl -
(1→2)-β-D-fructofuranoside
• MELEZITOSEin sap of some coniferous treesO-α-D-glucopyranosyl-(1→3)-O-β-D-fructofuranosyl-(2 → 1)-α-
D-glucopyranoside
TETRASACCHARIDE
STACHYOSE Galactose+galactose+glucose+fructos
e
PENTASACCHARIDE VERBASCOSE
Galactose+Galactose+galactose+glucose+fructose
POLYSACCHARIDES(GLYCANS)
Repeat units of monosaccharides or their derivatives,held by glycosidic bonds
Relatively or totally insoluble,tasteless
LINEAR
BRANCHED
POLYSACCHARIDES
HOMOPOLYSACCHARIDE
HETEROPOLYSACCHARIDE
GLUCAN
FRUCTOSAN
MANNANS
HOMOPOLYSACCHARIDE
STORAGE POLYSACCHARIDE
STRUCTURAL POLYSACCHARIDE
STARCHGLYCOGENDEXTRANSINULIN
CHITINCELLULOSE
STARCH
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 GLUCOSE
Acid hydrolysis
AMYLOSE
Amyloseα(1 → 4)Not soluble in waterForms hydrated micellesGives blue colour with iodineHelical coil with 6 glucose/turn
Amylopectin α(1→4) but branching points are α(1→ 6)Most abundant in plantsGives red violet colour with iodine
AMYLASES
Two types-α and βBoth hydrolyse only α- glycosidic bondsα- amylase = α(1→4)-glucan-4-
glucanhydrolaseβ-amylase = α(1→4)-glucan-4-
maltohydrolase Debranching enzyme- α (1→6)-
glucosidase or α (1→6)- glucan-6-glucanhydrolase
BREAKDOWN PRODUCTS OF STARCH
AMYLOPECTIN VIOLET
ERYTHRODEXTRIN REDACHRODEXTRIN NO
MALTOSE NO
STARCH BLUE
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
GLYCOGEN
Glycogen is used as energy source,glucose units are removed one at a time from non reducing endsGlucose is not stored in monomeric formStarch and glycogen are heavily hydrated
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
INULIN
D-fructose residues in β(2→1)In dahlia,garlic,onion,dandelionWhite, tasteless powderLevorotatoryNo dietary importance in humansUsed for estimation of body water
volume(ECF),assesing kidney functions through means of GFR
CHITIN
Second most abundant polysaccharide
CELLULOSE
Not attacked by α or β amylase
CELLULOSE
Schematic of arrangement of cellulose chains in a microfibril.
Every other glucose molecule is flipped over other due to β linkagesParallel orientation is favoured by intermolecular hydrogen bondX-ray diffraction of cellulose shows bundles of parallel chains to form fibrils
Not digested by mammals
CELLULOSE
Most abundant structural polysaccharide in plants
Cotton fibers are pure celluloseInsoluble in water D-glucose CELLULOSE partial hydrolysis Cellobiose
2,3,6-tri-O-methyl glucose
Complete hydrolysis
Exhaustive methylation
Strong acids
BIBLOGRAPHY
LEHNINGERHARPERTALWARBHAGVANDEBJYOTI DAS
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