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Polysaccharides (in Hindi)
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Dr Praveen Kumar Agrawal is teaching live on Unacademy Plus

Dr Praveen Kumar Agrawal
Ex - Faculty, Allen Kota, 22 Yrs Experience. Author - 17 books Known for best explanation Youtube : biology by pkagrawal

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thankyou sir it's very helpful for making notes and understanding concepts
Sir please u upload ur video on youtube also
Best explanation sir. Thank you.
  1. COURSE BIOMOLECULES Lesson Polysaccharides Dr. Praveen Kumar Agrawal


  2. Polysaccharides Polysaccharides or glycans are the large macromolecules, which have structural and functional significance in all forms of life. Polysaccharides of biological importance are - starch, glycogen, cellulose, chitin, mucopolysaccharides. Polysaccharides are the polymers of monosaccharides. Monosaccharides are held together by glycosidic bonds to form polysaccharides, e.g., Glucose units give rise to starch and glycogen etc. n(CsH1 206) Glucose units n(C6H1206) n 1(H2O) Polysaccharide (Starch)


  3. Classification of polvsaccharides Type Example Monosaccharides involved Starch Glycogen Cellulose Xylan Fructan Araban Chitin Pectin Inulin Mucopolysaccharides Complex carbohydrates, containing amino sugars and uronic Glucose Glucose Glucose Xylose Fructose Arabinose N-acetyl-D-glucosamine units Pectic acid (polymer of Galactouronic acid), galactan and araban Mainly Fructan +very few glucose units Homopolysaccharides Heteropolysaccharides acids Mixture of polysaccharides of galactans, xylans, arabinogalac- tans, glucomannans etc. Hemicellulose


  4. 1. Starch .Starch or 'amylum' is the main reserve food of plants. .Starch is mainly stored in amyloplasts in plant cells. Starch is formed by the plants by photosynthesis. Starch is an important food source. It is found in cereals, potatoes, legumes and other vegetables. Chemistry . Chemically starch is a homo-polymer of glucose, which is formed by the union of two polymers of glucose (a) .amylose and (b) amylopectin . (a) Amylose It is an unbranched chain of about 300 to 1000 a-D-Glucose units, which are joined together by 1-4 glycosidic bonds (b) Amylopectin . It is a branched structure, containing a-D-Glucose units, with 1-4 glycosidic linkage in the chain and 1-6 glycosidic . linkage at branching. .Starch can be hydrolysed to smaller polysaccharides such as limit dextrin and disaccharides (maltose) by amylase enzymes


  5. Amylose Amylopectin Glycogen


  6. 2. Glycogen It is the main storage carbohydrate in CH2OH animals. Hence it is also called animal starch It is also a polymer of glucose. Its formation from glucose is called Glycogenesis. In man it occurs in liver under the effect of hormone insulin OH OH 1-6, Glycosidic bono Chemistry Its structure is similar to that of amylopectin CH2OH CHOH but it is a highly branched structure (than amylopectin). OH HO H H It also consists of a -D-glucose units, which OH OH 1-4 glycosidic linkage in the chain and 1-6 glycosidic linkage at branching. Maltose 1-4, Glycosidic bond


  7. 3. Cellulose It is the main and the most important structural polysaccharides. It is chiefly present in the cell walls of plant cells. Along with hemicellulose (a low Mol. Wt. cellulose like polysaccharide) and lignin, forms the structural material of woody plants. . Cotton fibres contain the largest amount (90%) of cellulose while wood contains 20-25% of cellulose. Chemistry I It is insoluble in water and consists of about 6000 b-D-glucopyranose units (hexagonal glucose units), which are linked together by b-(1-4) glycosidic bonds. Cellulose can not be digested by many mammals, including human because they lack enzyme that . attacks the b- linkages. I In the gut of ruminants and other herbivores, there are micro-organisms that can attack b linkages, making cellulose available as a major source of energy.


  8. -D-glucose B-D-glucose


  9. Importance of cellulose It forms the main pulp of wood, cell walls, fibres and other structures of plants .It is a major energy source for ruminants and herbivores . Cellulose rich wood is used in furniture and other items of commercial value .Cellulose is the chief constituent of cotton fibres. Cellulose products are used in the manufacturing of paper Artificially produced fibres such as Rayon etc. are made from cellulose Cellulosic fibres are used in the preparation of ropes and jute bags. I Cellulose nitrate is used as an explosive Carboxymethyl cellulose is used as an emulsifier to provide fine texture to ice-creams, cosmetics and also used in medicines . . 4. Chitin . It is an important structural polysaccharide of invertebrate animals, forming their exoskeleton. Structurally it is formed by N-acetyl-D glucosamine units, which are joined together by b- (1-4) glycosidic linkage. It is also called fungal cellulos (as it forms the major part of cell wall in fungi) .5. Pectin Along with cellulose, pectin is present in the cell wall of all living plant tissues and fruit sap. Chemically, it is a mixture of mainly three polysaccharides-galactosans (galactans), araban and peptic acid (polymer of galactouronic acid)