Carbohydrates Classification , Structure , Sources With Example

                                         Carbohydrate        

Carbohydrate is one of the main biomolecules present in our body in the form of sugar ( glucose ), starch & fiber.  Besides providing energy to all over the body, carbohydrates play a significant role in many cellular activities. Carbohydrates are simply the combination of carbon, hydrogen, oxygen. They are also known as " the derivatives of aldehyde and ketone ." The general formula of carbohydrates is CN(H2O)N. In biochemistry the word carbohydrate is known by another name - Saccharide means sugar molecules. On the basis of the composition of sugar, molecules carbohydrate is divided into the following parts -

1. Monosaccharides - Here the word Mono means single& saccharide means sugar molecules & hence the term Monosaccharides. Monosaccharides are the molecules that have the involvement of only single sugar molecules.

Example - Glucose, Fructose.

Monosaccharide can further be divided into some different classes -


A. Triose - These are the smallest sugar molecules having a general formula  C3H6O3. Glyceraldehyde and dihydroxyacetone are examples of Triose.

B. Tetrose - The monosaccharides having four carbon atoms is known as  Tetrose. The general formula for tetrose is C4H8O4. e.g. Erytrose.

C. Pentose -  The monosaccharides having five carbon atoms in its chain and having a general formula   C5H10O5. Ribose, deoxyribose, and xylulose are the best example to explain pentose sugar.

D. Hexose -  The sugar molecules having six carbon atoms in its chain is known as Hexose.  The general formula for Hexose is C6H12O6.

 For Example - 

• Glucose - It is important for our bodies. Our body gets energy from it. It is present as a sugar in the blood. The normal level of glucose present in a healthy person is 80 - 120mg /ml.

Glycosuria - When glucose presents more than a normal level the disease is known as Glycosuria.

• Fructose - It is present in the fruits and honey. Fructose is changed into glucose in the intestine and supplied through the blood all over the body.

• Galactose - It is synthesized in the mammary glands and hydrolyzed to make lactose of the milk.

• Mannose - -Mannose is a nutritional supplement that can be found in cranberries, peaches, apples, other berries, and some plants.

E. Heptose -  The sugar molecules having seven carbon atoms in its chain is known as Heptose. The general formula for heptose is C7H14O7. E. g - Sedoheptulose.


2. Oligosaccharides - When more than two molecules of sugar involve forming a sugar then it is known as Oligosaccharides. In this water, molecules are eliminated and linkage is formed called Glycoside linkage. On the basis of the arrangement of carbon atom in the monosaccharide unit, the bond is known as alpha and beta bonds.

A. Disaccharides - The Disaccharides are composed of two same or different monosaccharides. The general formula for Disaccharides is Cn(H2O)n. 

For Example - 

• Maltose - It is also known as Malt Sugar. It is found in the germinating seeds. Generally 1, 4 linkages are found in Maltose. Maltose is used for beer production.

• Lactose - Lactose is composed of glucose and galactose. It is also called milk sugar. It is synthesized in the mammary glands.
  

• Sucrose - Glucose, and fructose are the building blocks for sucrose. Sucrose is also called table sugar or cane sugar. It is present in the fruits in varying amounts.

B. Trisaccharides -  The trisaccharides are composed of one or different monosaccharides. They are present in plants in small amounts. Their molecular formula is C18H32O16. For example - Raffinose.

C. Tetrasaccharides - The tetrasaccharides are sugar composed of four molecules of the same or different monosaccharides. Stachyose is an example of Tetrasaccharides. 



3. Poly Saccharides - It is a complex type of carbohydrate made up of several monosaccharides that are joined through a glycosidic bond. The general formula for Polysaccharide is (C6H10O5)n.


Types - Polysaccharide can be classified on the following basis


On the basis of Structure -

• Homopolysaccharides - The polysaccharide which is made up of similar kinds of monosaccharides, is known as Homopolysaccharides. Cellulose, glycogen is the example of Homopolysaccahrides.
• Heteropolysaccharides - The polysaccharide which is made up of more than two kinds of monosaccharides then it is known as Heteropolysaccharides. Agar, pectin is the example of heteropolysaccharides.

On the basis of functions -

• Food storage Polysaccharides - The types of sugar that are present in a reservation form and whenever there is a need for sugar it hydrolyzes into sugar and provides energy to the body. There are following polysaccharide which is used in this category -

Starch - It is present in the store form in the rice, cereals, potato, and serves as energy-storing material. It consists of two types of molecules Amylose and Amylopectin. Amylose is a single chain and Amylopectin is branched. Basically starch is a polymer of glucose unit linked together in an alpha 1,4 glycoside linkage.


Glycogen - Glycogen is also called animal starch. It is present in the muscles and liver of animals. It is composed of glucoside unit joined together through alpha 1,4 or 1,6 glycosidic linkage.

• Structural Polysaccharides - 

Cellulose - It is the important constituent of the cell wall part and provides support to the cell wall of the plant. It is a linear chain of glucose units joined together through beta 1,4 glycosidic linkage. Cellulose is rigid and insoluble in water.

Chitin - Chitin is found in the cell wall of fungi, algae and it is also present in the exoskeleton of arthropods as it is insoluble in water. It is a long-chain polymer of N - acetyl glucosamine.

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