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
- Simplest carbohydrate unit or monomer
- that cannot be hydrolysed further
- General formula (CH2O)n
- Minimum no of Carbon atom is 3
- Example: glucose, fructose
Two monosaccharide units joined by glycosidic bond
Example: Glucose + Glucose=Maltose (Disaccharide)
Glucose + fructose= Sucrose
Watch here What is glycosidic bond?
Carbohydrates usually made up of 3-10 monosaccharide units joined by glycosydic bond
- 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.