Carbohydrate and its classification

Carbohydrate

Polyhydroxy aldehyde and ketone and their derivative.

• Carbohydrates are composed of carbon hydrogen and oxygen possessing a common empirical formula 

Occurance

carbohydrate are most abundant of all biochemical compound and constitutes more than 50% of total biochemical matter.

 they are widely distributed in plant, animal and microbes.

• Synthesized in green plant and algae from water and CO2 using solar energy.

Physiological role and biological importance

The carbohydrate have many function in the living organisms

1. Chief source of energy
2. Reserve or storage form of energy in plant (starch, inulin) and animals(glycogen)
3. Structural element in plant cell wall (cellulose), exoskelton of some insect and crustacea (chitin), cell wall of certain microorganism (peptidoglycans), skin and connective tissue of animal (mucopolysaccharides)
4. Important component of nucleic acid, co-enzyme and flavoprotein (some example Ribose)
5. They involve in cell recognition, contact inhibition and also have antigenic.

Classification of carbohydrate

Based on number of monomeric sugar unit present.

Carbohydrate can be classified into three main group 

1. monosaccharide, 
2. oligosaccharides, and 
3. polysaccharide.

Monosaccharide

Monosaccharide are simple sugar.

 consists of single polyhydroxy aldehyde or ketone group that cannot be hydrolysed into smaller units.

 they serve as the building block of the more complex sugar.

Monosaccharide also known as simple sugar.

• Carbonyl group is  aldehyde the sugar is called Aldose..(name ends ose)
• Carbonyl group content ketone called ketose(name ends ulose)

the simplest monosaccharide are 3 carbon trioses glycerylaldehyde and dihydroxyacetone.

• Glucose is  most abundant monosaccharide,

 major fuel for most organisms and the basic building block of many oligosaccharides and polysaccharide.

General property of monosaccharide

• Monosaccharide are polyhydroxy aldehyde and ketone and their derivatives.
• Simplest form of carbohydrate which cannot be hydrolysed to other sugar unit.
• generally monosaccharide are white crystalline solid.
• Most of them have a sweet taste
• free aldehyde aur ketone group are able to reduce metal ions under alkaline condition ,they are excellent reducing agent

Oligosaccharides

sugar consists of a short chain of 2 to 10 monosaccharide unit linked by the glycosidic bond  with elimination of water molecule.

depending on the number of monosaccharide units  are linked , the oligosaccharides are further classified

•  disaccharide (two sugar unit),
• trisaccharide (3 sugar unit),
• tetrasaccharide (4 sugar unit) etc.

Disaccharide

two monosaccharide linked  by the glycosidic bond with the elimination of one molecule of water.

General properties of disaccharide

• free aldehyde group or ketone group can reduce fehling solution, hence are called reducing disaccharide.
• Disaccharide can be hydrolysed into their constituent monosaccharide
• Disaccharide  may exist in white crystalline solid , soluble in water and sweet in taste.
• Disaccharide are not fermented by yeast directly but they are first hydrolysed to constituent monosaccharide which in turn are fermented.

most abundant disaccharide in nature are maltose ,sucrose and lactose.

Maltose

Maltose is a disaccharide formed linking two unit of a alpha-D -glucose through Alpha 1 4 glycosidic bond with the elimination of one molecule of water.

• Maltose is a reducing sugar.
• Maltose is prepared from sprouting Barley is an excellent source of maltose.

Sucrose

• Sucrose is known as cane sugar or beet sugar or saccharose or invert sugar .

Sucrose is disaccharide made up of one molecule of each of alpha- d -glucose and beta- d- Glucose ,

The linkage involving the potential aldehyde group of a carbon atom 1 of  glucose and the ketonic group of the carbon atom 2 of fructose linkage.

• It is non reducing sugar.
• it is hydrolysed by acid or enzymes sucrase(invertase) into glucose and fructose.
• Sucrose is most abundant oligosaccharide and ubiquitous in plant.

Sucrose is manufacture from sugarcane and sugar beet.

Lactose

• Lactose is milk sugar.
• It is reducing sugar.
• It reduce fehling solution.
• Lactose is hydrolysed by the enzyme lactase into its constituent hexose.
• Lactose is not produce in plants.

Trehalose

Trehalose are made up two glucose unit link through two anomeric carbon atom.

• Trehalose is non reducing sugar.

Trehalose carbohydrate present in insect and fungi serve as storage carbohydrate.

Polysaccharide or glycans

Carbohydrate which are polymerized anhydride

Number of simple sugar which are join by glycosidic bond.

General properties

Polysaccharide are tasteless, apparently amorphous, some crystalline.

• Mostly insoluble in cold water but form sticky or gelatinous solution.
• Hydrolysed by acid or enzymes, they are broken down into various intermediate product.

High molecular weight And complex form.

Pectin contain arabinose, galactose and glacturonic acid.

Hemicelluloses are homopolymers of D-xylose linked by beta 1,4- bonds.

Cellulose are cotton fibre (98 percentage)

Jute(50-70 percentage)

• cellulose and its derivatives are widely used in textiles, films, and plastics.

Chitin

Chitin is Structure homopolysaccharide.

• Chitin made up of N-acetyl glucoamine residue in beta- 1,4 linkage.

Chitin present in the skeleton of  crustaceous insects, earthworms and mollusks

• Chitin is second most abundant organic substance on earth.