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Classification Of Carbohydrates

Renu Maurya

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 Cn (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.    

Exam Important

  • Major source of energy for human beings is carbohydrates, as Glycogen (45-65%)
  • Glucose is dextrorotatory hence called as Dextrose.
  • The only metabolic fuel for mature erythrocytes in fed and starving state is glucose.
  • Galactose is the constituent of lactose (milk sugar) and part of glycosaminoglycan in proteoglycans  glycolipids.
  • Fructose is present in honey, seminal fluid.
  • Glycosaminoglycan with no uronic acid is Keratan sulphate.
  • General formula- Cn (H2O)n  (for monosaccharide)
  • If ring structure formed by cyclization is six sided called as pyranose ring (pyran) (seen in glucose)
  • Dihydroxyacetone (no asymmetric carbon atom)
  • Mannose is an epimer of glucose
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