Disachharides with structures and functions.pptx

carbohydrate

1. DISACCHARIDES: Definition: A disaccharide is a sugar consist of two Monosaccharides held together by gylcosidic bond. Properties: 1. Soluble in water 2. Crystalline 3. They are sweet in taste. Types: 1: Reducing disaccharides: Free aldehyde or keto group. E.g maltose, lactose 2.Non reducing disaccharides: No free aldehyde or keto group. E. g sucrose.

2. Maltose: Composed of two alpha-D- glucose unit held by alpha(1 - 4) gylcosidic bond. Free aldehyde group present on C1 of second glucose. Maltose can be break down into two molecules of glucose by hydrolysis.

3. Sucrose: Commonly known as cane sugar. Composed of alpha-D-glucose and beta-D- fructose. Held together by (alpha1 - beta2) gylcosidic bond between C1 of alpha glucose or C2 of beta fructose. Non reducing sugar or cannot form osazones . Important source of dietary carbohydrates. It is sweeter than others.

4. Inversion of sucrose: Sucrose is dextrorotatory. When hydrolyzed,sucrose becomes levorotatory. The process of change in optical rotation from dextrorotatory to levorotatory known as inversion. Hydrolysed mixture of glucose and fructose known as invert sugar.

5. Lactose: Commonly known as milk sugar. Composed of beta-D- glactose or beta-D-glucose. Held together by beta( 1 - 4 ) gylcosidic bond. Lactose exhibits Reducing properties or form asazones . Lactose of milk is most important carbohydrate in nutrition of young mammals.

6. Lactulose: It is a synthetic disaccharide contains g lactose or fructose. It is neither digested not absorbed in intestine. Lactulose is used in treatment of hepatic encephalopathy, disorder characterized by elevated plasma ammonium levels.

7. POLYSACCHARIDES: They are the polymers of Monosaccharides. Polysaccharide may be linear as well as branches polymers. TYPES: 1. Homopolysaccharides : On hydrolysis yield only single type of Monosaccharide. Glucans are the polymers of glucose or fructosans are the polymers of fructose. 2.Heterpolysaccharides: On hydrolysis yield a mixture of Monosaccharide or their derivatives.

8. Example of homo POLYSACCHARIDES: Strach Dextrins Dextrans Inulin Glycogen Cellulose Chitin

9. Starch: Carbohydrate reserve of plant, dietary source for higher animals including man. Starch found in cereals, roots, tubers, vegetables etc Composed of D-glucose units held by alpha- glycosidic bonds. Consist of amylopectin or amylose.

10. Amylose and amylopectin: Amylose: Linear chain 20percent of starch It has 1-4 glycosidic linkages. Amylopectin: Branched chain 80 percent of starch It has 1-6 glycosidic linkages.

11. Glycogen: 1. Carbohydrate reserve of animals 2. Often referred as animal starch. 3. High concentration in liver muscle or brain. 4. Found in plants but do not possess cholorphyll . 5. Structure of glycogen is similar to amylopectin with more number of branches.