Carbohydrate Chemistry PDF - Lecture Notes

 II. Disaccharides: Maltose, a cleavage product of starch (e.g., amylose), is a disaccharide with an (1→ 4) glycosidic link between C1 - C4 OH of 2 glucoses. It is the  anomer (C1 O points down). 6 CH2OH 6 CH2OH 5 O...

 II. Disaccharides: Maltose, a cleavage product of starch (e.g., amylose), is a disaccharide with an (1→ 4) glycosidic link between C1 - C4 OH of 2 glucoses. It is the  anomer (C1 O points down). 6 CH2OH 6 CH2OH 5 O 5 O H H H H H H 1 4 1 4 OH H OH H OH O OH 3 2 3 2 H OH H OH maltose 1 2  6 CH2OH 6 CH 2OH 5 O 5 H H O OH H H 4 1 O 4 1 OH H OH H OH H H 3 2 3 2 H OH H OH cellobiose Cellobiose, a product of cellulose breakdown, with (1→ 4) glycosidic linkage, is  anomer (O on C1 points up).  Polysaccharides are composed of more than 10 monosaccharide units linked by glycosidic bond.  It include two type - Homopolysaccharide - Heteropolysaccharide  Starch Starch is the chief storage form of carbohydrates in plants. e.g. rice, potatoes. Hydrolysis by amylase in to maltose and isomaltose Starch granules contain parts, amylose in the inner part (15-20%) and amylopectin in the outer(80-85%) 1- Amylose is composed of 300-1000 of αD-glucose connected by (1→4) glycosidic linkage forming an unbranched chain. CH2OH 6CH OH CH2OH CH2OH CH2OH 2 O 5 O H O O H H O H H H H H H H H H H H H OH H 1 4 OH H 1 OH H OH H OH H O O O O OH OH 2 3 H OH H OH H OH H OH H OH amylose  2- Amylopectin is a branched polysaccharide; each branch is formed 24-30 αD-glucose connected by (1→4) glycosidic linkage within the branches and (1→6) glycosidic linkage at the branching points. CH2OH CH2OH H O H H O H amylopectin H H OH H OH H 1 O OH O H OH H OH CH2OH CH2OH 6 CH2 CH2OH CH2OH H O H H O H H 5 O H H O H H O H H H H H H OH H OH H OH H 1 4 OH H OH H 4 O O O O OH OH 2 3 H OH H OH H OH H OH H OH  CH2OH CH2OH H O O glycogen H H H H H OH H OH H 1 O OH O H OH H OH CH2OH CH2OH 6 CH2 CH2OH CH2OH H O H H O H H 5 O H H O H H O H H H H H H OH H OH H OH H 1 4 OH H OH H 4 O O O O OH OH 3 2 H OH H OH H OH H OH H OH Glycogen, is the storage form of glucose in animals. It is mainly present in skeletal muscles and liver. It is highly branched chain. Each branch is composed of 12-14 αD-glucose connected by (1→4) glycosidic linkage within the branches and (1→6) glycosidic linkage at the branching points. The highly branched structure permits rapid glucose release from glycogen stores, e.g., in muscle during exercise.  CH2OH 6CH OH CH2OH CH2OH CH2OH 2 O 5 O O H O H O OH H H H H H H H H OH H 1 O 4 OH H 1 O OH H O OH H O OH H OH H H H H 2 H 3 H OH H OH H OH H OH H OH cellulose Cellulose, a major constituent of plant cell walls. It is formed of long unbranched chains of  D glucose connected together with (1→4) linkages. The presence of cellulose in diet is important as it increase the bulk of food, which stimulates intestinal contraction and prevent constipation.  Most of the GAGs are conjugated to a protein core, the product is termed proteoglycan.  They are composed of core of protein (5 %) to which long chain of GAGs are attached(95%).  Proteoglycan monomer is formed of a core protein to which long linear carbohydrate chains are attached.  Proteoglycan monemer is a polyanion due to the coo- SO3- groups so:- 1. The chains of repeating disacchride units remain separated by repulsion between –ve charges giving the proteoglycan monomer its bottle brush appearance. 2. The chains bind cations as Na and K so attract water, by osmotic pressure, into ECM giving it a gel-like consistency  They are important constituents of extracellular matrix. The proteoglycan interact with a variety of protein in such as collagen and elastin, and these interaction are important in determining the structural organization of the matrix  Hyaluronic acid proteoglycans Involved in wound healing (repair). Hyaluronidase enzyme (spreading factor): This enzyme can hydrolyse hyaluronic acid in the ground substance of connective tissue. ▪ It secreted by some bacteria helps in spread of infection. ▪ It is also present in sperms (head) and help the process of ovum fertilization.  Heparin proteoglycan;- - Is an important anticoagulant (prevent thrombus formation). Activate antithrombin and inactivates coagulation factor. - It bind to lipoprotein lipase enzyme and increases its release from the capillary wall to the plasma. Keratan sulfate proteoglycan important for transparency of the cornea. Heparan sulfate proteoglycan Associated with plasma membrane of cell (receptors and cell-cell interaction)  Proteoglycans form huge aggregate by the association of proteoglycan monomers with a molecule of hyaluronic acid.  Present in cartilage  They are protein to which oligosacchride chain are bound.  The carbohydrate contents of glycoprotein are less relative to proteoglycan.  8 monosacchride are commonly present in oligosacchride chain:- (galactose, glucose, masnnose, xylose, fucose, N acetylglucosamine, N acetylgalactosamine and N acetylneuraminic acid)  Site:- mucous fluids, blood and cell membrane.  The carbohydrate content of glycoproteins is variable, it is 1% in collagen, 4% in IgG, 50% in mucins and 85% in ABO.  The products of hydrolysis of lactose are: 1. α-glucose and α-fructose 2. α-glucose and α-galactose 3. α-galactose and α-ribose 4. α-fructose and α-galactose  Starch is a polymer made from the following monomer: 1. β-glucose 2. α-glucose 3. α-galactose 4. α-fructose