General Veterinary Biochemistry

CLASSIFICATION OF CARBOHYDRATES

• Based on the sugar units they contain, carbohydrates are classified into four groups, as
  • Monosaccharides
  • Disaccharides,
  • Oligosaccharides  ( a small polymer of sugar)
  • Polysaccharides
• Monosaccharides are simple sugars, consisting of single polyhydroxy aldehyde or ketone unit. They cannot be hydrolyzed to yield simpler forms of sugar.
• They can be subdivided into trioses, tetroses, pentoses, hexoses, heptoses and octoses, depending upon the number of carbon atoms they possess.
• Carbohydrates with an aldehyde as their functional group are called as Aldoses. Those with keto as functional group are called as ketoses.

Name	Empirical Formula	Aldoses	Ketoses
Trioses	C3H6O3	Glycerose	Dihydroxy acetone
Tetroses	C4H8O4	Erythrose	Erythrulose
Pentoses	C5H10O5	Ribose	Ribulose
Hexoses	C6H12O6	Glucose	Fructose

• Disaccharides Yield two  molecules of the same or different monosaccharides when hydrolyzed. Examples are sucrose, lactose, and maltose.
• Oligosaccharides Yield 3–6 monosaccharide units on hydrolysis. Eg. maltotriose and raffinose
• Polysaccharides Yield more than 6 molecules of monosaccharide on hydrolysis. Examples of polysaccharides are starch, cellulose, glycogen and dextrins.
• The polysaccharides may be linear or branched eg. Cellulose is a linear polysaccharide and starch is a branched polysaccharide.
• Polysaccharides are sometimes called as hexosans or pentosans, depending upon the type of the monosaccharides they yield on hydrolysis eg., glycogen -hexosan