Glycogen, cellulose and starch have the same monomer unit, but their physical and chemical properties differ because of their configuration difference. Why it is so?
Dear Anju,
the reason why the above mentioned biopolymers differ in their physical and chemical properties is simple:
Glycogene is present in liver, it is amorphous and easy to degrade via ezymatic processes at the consequent release of energy. Glycogene is built from 1,4 and 1,6 alpha D-glucopyranose units, it is amorphous and water soluble. Average molecular weight approx. 10 5.
Cellulose is present in plant species, linear chains of macromolecules are oriented and form elementary fibriles, then microfibriles and fibriles, thus creating supramolecular structure of this biopolymer. The cause of macromolecules orientation and aggregation are intermolecular hydrogen bonds. Characteristic for supramolecular cellulose is its contents of amorphous and highly oriented /cristalline/ portion. The building unit is 1,4 beta- D-anhydro-glucopyranose. DP of cell. varies within 102 - 104 according to the plant, age and the method of isolation. Cellulose is not soluble in ordinary solvents. It is soluble in various complex moieties, dissociated in polar media on large size complex anions or cations and their counter-ions /FETNa, Schweitzer solvent, Cuoxame, Cadoxene etc./. The principle of cellulose dissolution in this case is in gradual decomposition of supramolecular structure of cellulose, and formation of gelated systems of individual solvated macromolecules.
Starch consists of 1,4 alpha- D-anhydro-glucopyranose /respectively also of 1,6 alpha-D-anhydro-glucopyranose in the case of amylopectine/. Starch consists of branched amylopectine fraction and of linear-spirallike amylose fraction. The presence of alpha anameric D-glucose and space branching /amylopectine fraction of starch/ prevents macromolecules of starch from forming highly oriented fibrillous supramolecular structures. Starch is generally amorphous, in case of amylose the paterns of oriented supermolecular structures were sometimes observed. DP of starch is much lover then the same parameter of cellulose /approx. 102 - 103 /. Starch, on contrary to cellulose, is water soluble, or partly water soluble. It is present in parenchymaatic cells, roots and different fruits.
Regards,
R.S.
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