POLYSACCHARIDES . By SANGH PARTAP Department of Pharmacy Teerthanker Mahaveer University, Moradabad, U.P., INDIA. Definition.
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Department of Pharmacy
TeerthankerMahaveer University, Moradabad, U.P., INDIA
On hydrolysis yield only one type of monosaccharide unit.
Example- cellulose, inulin, starch etc.
On hydrolysis yield more than one type of monosaccharide unit.
Example- α- heparin, hyaluronic acid etc.
Of plant and most widely distributed carbohydrate.
Structure and properties
Mol.formula of Cellulose has been found to be (C6H10O5)n from analytical data.
When Cellulose is hydrolysed with fuming HCL it give D- glucose in 95-96% yield.This reaction reveal that Cellulose is made up of glucose unit.It means that the structure of Cellulose is based on the D- glucose unit.
Methylation,acetylation and nitration of Cellulose produce trisubstitution product as a max. substituted product, it means that each glucose unit present possesses 3 OH group in an uncombined state.
Fully methylated cellulose, when subjected to hydrolysis yield 2,3,6 tri-O-methyl D- glucose (90%) as main product and also 2,3,4,6 tetra-O-methyl D- glucose 0.6% as minor product.
Haworth methylation method:-
Cellulose is completely methylated in inert atmosphere then methylated cellulose is hydrolysed by dill. Acid to cleave the glycosidiclinkage.thenonreducing end will yield 2,3,4,6 tetra-O-methyl D- glucose whereas all other will undergo hydrolysis to yield 2,3, tri-O-methyl D- glucose. The two hydrolytic product are seprated by chromatographic tech.
Hence by knowing the % of tetra methyl derivative or ratio of tetra methyl- tri methyl derivative.
This method is known as the end-group assay.
the amount of formic acid is estimated by the titration method. This estimation gives the value of chain length.
Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol.
Enzymatic hydrolysis amylose give maltose. Maltose is 4-o-(α-glucopyranosyl) –D-glucopyranose, all the glucose unit in starch are linked through C1α and C4. hence amyloseposesses the foolowing str. Which explain the hydrolysis product.
The repeating unit consists of D-galactose (β 1 4)-linked to 3,6-anhydro-L-galactose (in which an ether ring connects C-3 and C-6). These units are joined by ((α1 3)-) glycosidic links to form a polymer 600 to 700 residues long. A small fraction of the 3,6-anhydrogalactose residues have a sulfate ester at
Polysaccharides (glycans) serve as stored fuel and as structural components of cell walls and extracellular matrix.
Homopolysaccharides fold in three dimensions. The chair form of the pyranose ring is essentially rigid, so the conformation of the polymers is determined by rotation about the bonds to the oxygen on the anomeric carbon.
Glycosaminoglycans are extracellular heteropolysacch- arides in which one of the two monosaccharide units is a uronic acid and the other an N-acetylated amino sugar. Sulfate esterson some of the hydroxyl groups give these polymers a high density of negative charge, forcing them to assume extended conformations. These polymers (hyaluronate, chondroitin sulfate, dermatan sulfate, keratan sulfate, and heparin) provide viscosity, adhesiveness, and tensile strength to the extracellular matrix.