Classification Of Carbohydrates

• Carbohydrates are classified based on number of individual monosaccharides units into 4 groups-

1. Monosaccharides
2. Disaccharides
3. Oligosaccharides
4. Polysaccharides 

1. Monosaccharides-

• General formula is C_n (H₂O)_n
• Monosaccharides cannot be hydrolyzed further into simple carbohydrates and called as Simple sugars.
• If ring structure formed by cyclization is six sided called as pyranose ring (pyran)

• If ring structure is five sided it is furanose ring (furan)

• Monosaccharides are further divided into-

I)   According to the, number of carbon atoms-

• Trioses (3C)
• Tetroses (4C)
• Pentoses (5C)
• Hexoses (6C)
• Heptoses (7C)
• Nanoses (9C) 

II)  According to the functional group,

• Aldoses
• Ketoses

A) Aldoses- When the functional group in monosaccharides is an aldehyde group.

• Glyceraldehyde- 3C
• Erythrose- 4C
• Ribose, Xylose (Epimer of Ribose), Arbinose- 5C
• Glucose, galactose, mannose- 6C 

B)Ketoses- When the functional group in monosaccharide is an ketone group.

• Dihydroxyacetone (no asymmetric carbon atom)
• Erythrulose
• Ribulose, Xylulose (Epimer of Ribulose)
• Fructose
• Sedoheptulose

Significance of Monosaccharides-

• Glucose is an aldohexose.
• Most predominant sugar in human beings.
• Glucose is dextrorotatry, hence called Dextrose.
• Major energy source in organs is glucose-

1. Brain
2. Renal Medulla
3. Cornea
4. Retina
5. Testis
6. RBC

• The only metabolic fuel for mature erythrocytes in fed state and starving state is Glucose.
•  Fructose is a ketohexose.
  • Present in fruit juice, honey, sugarcane.
  • Present in Seminal fluid.
• Galactose is a constituent of lactose (milk sugar)
• Part of glycoprotein, glycosaminoglycan in proteoglycans and glycolipids.
• Mannose present in plants and occurs in Glycoproteins and Mucoproteins.
• Mannose is an epimer of glucose 

*All the hexoses are reducing sugars.    

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