Carbohydrates by Dr.U.Srinivasa, Professor and HOD,

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CARBOHYDRATES AND RELATED PRODUCTS:

CARBOHYDRATES AND RELATED PRODUCTS Dr.U.Srinivasa , M. Pharm., M.Phil., Ph.D. Professor and Head, (Dept. of pharmacognosy ) Srinivas college of pharmacy, Mangalore. Email. usreenivas1966@rediffmail.com

Carbohydrates:

Carbohydrates Carbohydrates are first or primary products of photosynthesis. Functions : They are the reserve materials of plants (starch) and of animals (glycogen) They supply energy and are structural or skeletal substances of plants (cellulose)

Definition:

Definition Carbohydrates were defined as a group of compounds composed of carbon (C), Hydrogen (H) and Oxygen (O ). They are expressed by formula ( CH 2 O) n i.e. is hydrates of carbon.

Definition:

Definition They are also defined as polyhydroxy aldehydes or polyhydroxy ketones or compounds that on hydrolysis produce either of the above

Classification::

Classification: Carbohydrates are mainly classified into two groups Sugars or saccharides and Polysaccharides

Sugars or saccharides:

Sugars or saccharides They are also called as “Saccharides” ( Sakcharon in Greek meaning sugar), chemically a simple sugar is a ketonic or aldehydic substitution product of a polyhydroxy alcohol.

Sugars or Saccharides :

Sugars or Saccharides Monosaccharides Disaccharides Trisaccharides Tetrasccharides

Sugars or saccharides:

Sugars or saccharides Monosaccharide are sugars, which cannot be further hydrolyzed to simple sugars. However, they are classified according to the number of carbon atoms in sugar molecules

Types:

Types i) Bioses : They contain two carbon atoms. They do not occur in free in nature ii)Trioses: They contain three carbon atoms, but in the form of phosphoric esters, eg Glyceraldehyde

Types:

Types iii) Tetroses : They contain four carbon atoms, eg : Erythrose iv) Pentoses : They are very common in plants and are the products of hydrolysis of polysaccharides like hemicelluloses,mucilages and gums. (Contain five carbon atoms ) Eg : Arabinose, Ribose, xylose

Types:

Types V. Hexoses : They contain 6 carbon atoms and are abundantly available carbohydrates of plant kingdom. They are further divided into 2 types - Aldoses : They contain an aldehyde group, eg : Glucose, manose , galactose Ketoses: They contain ketone group, eg : Fructose and sorbose

Types:

Types VI) Heptoses : They contain seven carbon atoms, eg : Glucoheptose and monoheptose

Disaccharides:

Disaccharides Carbohydrates which on hydrolysis yield two molecules of monosaccharides are called as disaccharides Eg : Sucrose - on hydrolysis - Glucose + Fructose (Sugarcane) Eg : Lactose - on hydrolysis - Glucose - Galactose (Cow’s milk)

Trisaccharides::

Trisaccharides: Carbohydrates , which on hydrolysis yield three molecules of monosaccharide’s are called as trisaccharides . Eg : Raffinose – on hydrolysis - Glucose + Fructose + Galactose Eg : Gentianose - on hydrolysis - Glucose + Glucose + Fructose (Gentian roots)

Tetrasaccharides:

Tetrasaccharides On hydrolysis yields 4 molecules of monosaccharide's, eg : Stachyose

II. Polysaccharides:

II . Polysaccharides On hydrolysis yields an indefinite number of monosaccharide. Eg starch, cellulose

Difference between Gums and Mucilage:

Difference between Gums and Mucilage Gums Mucilage They are the pathological products consisting of ca , mg, k, salts of complex substances They are the physiological products related to gums On prolong heating with dilute acids forms sugars and uronic acids They are sulphonic acid esters They are not normal products of plant metabolism but as a result of injury / in abnormal / in unfavourable condition the gums are produced Mucilage are the normal products and are produced without injury to the plant They are plant exudates They are not exudates of plant Gums are used in dental and other adhesives and as bulk laxatives. Eg : Acacia, tragacanth , Mucilage are used as demulcents , bulk laxatives Eg , Isapghula , linseed, agar

Identification of carbohydrates:

Identification of carbohydrates Molisch’s test: The test is positive with soluble, as well as insoluble carbohydrate. Solution of carbohydrate and few drops of Molisch’s reagent and few drops of concentrated sulphuric acid - Purple colour or violet ring at the junction of the two liquids Fehling’s test: Solution of carbohydrate and few drops of Fehling’s solution A and Fehling’s solution B. Heat the mixture -- Brick red ppt.

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