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
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.

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