What are Carbohydrates? How are they Classified? with simple video

Definition: Carbohydrates are bio molecules which are polyhydroxy aldehydes or ketones made  up of Carbon C, Hydrogen H and Oxygen O in the ratio (1:2:1)

Classification of Carbohydrates

This is a simplified 8 minute video on different classification of carbohydrates

A. Based on No. of Carbohydrate Units

1. Monosaccharides

• Simplest carbohydrate unit or monomer
•  that cannot be hydrolysed further
• General formula (CH2O)n
• Minimum no of Carbon atom is 3
• Example: glucose, fructose

2. Disaccharides:

Two monosaccharide units joined by glycosidic bond

Example: Glucose + Glucose=Maltose (Disaccharide)

                   Glucose + fructose= Sucrose

Watch here What is glycosidic bond?

3. Oligosaccharides

Carbohydrates usually made up of 3-10 monosaccharide units joined by glycosydic bond

Eg: Raffinose

4. Polysaccharides

• Complex Carbohydrates made up of hundreds of monosaccharide unit s joined by glycosydic bond
• Structural Polysaccharides like Cellulose in plants
• Storage Polysaccharides like starch in plants and glycogen in animals

B. Based on functional group

• Aldoses: Carbohydrates with aldehyde(-CHO) functional group Eg: Glucose
• Ketoses: Carbohydrates with ketone (=C=O) functional group Eg: Fructose

C. Based on no. of carbon atoms

• Simplest monosaccharide has 3 carbon atom called as Triose. Eg: Glyceraldehyde
• Tetrose: Monosaccharide with 4 carbon atom Eg: erythrose
• Pentose: 5 carbon atom Eg: pentose
• Hexose: 6 carbon atom Eg: Glucose
• Heptose: 7 carbon atoms Eg: sedoheptulose

D. Based on Rotation (Dextro and Levo)

• Based on stereochemistry of the highest numbered chiral carbon of the Fischer projection.
• If the hydroxyl group of the highest numbered chiral carbon is pointing to the right, the sugar is designated as D (Dextro: Latin for on the right side). 
• If the hydroxyl group is pointing to the left, the sugar is  Levo (Levo: Latin for on the left)
• Most naturally occurring carbohydrates are of the D-configuration.