Carbohydrates

Carbohydrates are the plants primary metabolism product. Carbohydrates are divide into two classes mainly : Saccharides also known as sugars and polysaccharides. They consist of mainly carbon, hydrogen and oxygen elements. Carbohydrates present in plants one of the abundant available chemical compound. Plants cell wall is made up of cellulose. Sugars can form complex with non-sugar moiety one of the example of this is glycoside. Some of carbohydrates are crystalline, sweet in taste and soluble in water as well as low molecular weight. Eg fructose, sucrose and glucose whereas some carbohydrates are high molecular weight less soluble n water, tasteless and amorphous in nature also called as polymer eg. Pectin, gum, cellulose, starch. Saccharides are classify into monosaccharides, disaccharides and trisaccharides based upon chemical structure.

Monosaccharides

Monosaccharides are sugars contain three to nine carbon atom in which five and six carbon containing sugars are abundantly available. Sugars containing aldehyde group known as aldose sugar examples is glucose and ketone group known as ketoses examples is fructose. Sugars are undergoes oxidation to give acid as a product eg. Uronic acid ( galactouronic, glucouronic acid).

Monosaccharides are known as simple sugars since they do not further hydrolysed. They are classified depend upon sugar molecule containing number of carbon atom.

1. Two carbon atoms containing sugar is known as bioses they are not available free form in nature

2. Three carbon containing sugars are known as trioses mainly available inform og esters of phosphoric acid.

3. Four carbon containing sugars are known as tetrose eg. D-erythrose, D-Threose (C₄H₈O₄)

4. (C₅H₁₀O₅) empirical formula sugars are present commonly in plants and polysaccharides ( hemicelluloses, gums and mucilage on hydrolysis giving sugars known as pentose eg. Ribose, xylose and arabinose.

5. (C₆H₁₂O₆) sugars are containg six carbon atoms and are available in plants known as Hexoses. They further divided into ketoses and aldoses. They are products of hydrolysis of polysaccharides like starch and inulin.

6. Some sugars are containing 7 carbon atoms known as heptoses having values in photosynthesis of plants and metabolism of glucose in animals and stored in some plants eg. Mannoheptoses and glucoheptoses

Disaccharides

It gives two monosaccharides molecules on hydrolysis thus called as disaccharides.

Sucrose Hydrolysis .

(Cane-sugar) glucose + fructose

Trisaccharides

It gives three monosaccharides molecule on hydrolysis thus called as trisaccharides.

Hydrolysis

Raffinose glucose + fructose + galactose (in beet and manna)

Hydrolysis

Gentianose glucose + glucose + fructose (gentian roots)

Scillatriose (squill), mannotriose (manna) and phanteose (psyllium)

TETRASACCHARIDES

This gives four sugars on hydrolysis thus called as tetrasaccharides. Examples are as follows:

Hydrolysis

Stachyose (manneotetrose) glucose + fructose + galactose + galactose

plants containing tetrasaccharides are Stachys japonic and manna Fraxinus-urnus.

Polysaccharides

Polysaccharides are carbohydrates which on hydrolysis giving imprecise number of monosaccharides. Monosaccharides undergoes condensation and evolution of water molecule to produce polysaccharides. Petosans and hexosans are two classes of polysaccharides depending upon hydrolysis. Cellulose, inulin and starch is hexosans whereas xylan is pentosans. Cellulase is an enzyme found in animals hydrolysed cellulose which is made up of glucose units joined by β -1,4 linkages, whereas α-1, 4; α-1, 6 units linked glucose is known as starch. Polysaccharide derivatives important pharmaceutically are polyuronides ( i.e. Alginic acid, pectin, mucilage and gums. Polyuronides are the complex substances with calcium, magnesium and potassium salts and pathological product known as Gums.

It will give mixtures of sugars and uronic acid after . On long time boiling with dilute acids, Sulphuric acid esters derivative complex polysaccharides are physiological product known as Mucilage. Cellulose decomposed product known as gum and mucilage. Aldobionic acid a-pectic acid esters of neutral methoxy esters is known as Pectin as a water soluble compound from the inner portion of the rind of citrus fruits. Gums and mucilages are closely related to hemicelluloses in composition, except that the sugars produced by hemicelluloses are glucose, mannose and xylose, instead of galactose and arabinose. Gums having colloidal properties and high molecular weight compound and hydrophilic and hydrophobic compound. In appropriate solvent or swelling agent. They produce gels, highly viscous suspensions 'or solutions.