Carbohydrates are polyhydroxyl aldose or ketose can be represented by the
molecular formula Cm(H2O)n.
Classification of carbohydrates:
1.According to functional group:
a. Aldose: Aldehyde groups are present as main functional groups.
b. Ketose: Ketone groups are present as main functional groups.
2.According to the number of C atoms present in the molecule:
a. Triose: 3 carbon atoms present. eg. glyceraldehyde C3H6O3
b. Tetrose: 4 carbon atoms present. eg. erythrose C4H8O4
c. Pentose: 5 carbon atoms present. eg. ribose C5 H10O
d. Hexose: 6 carbon atoms present. eg. glucose, fructose C6 H12O6
e. Heptose: 7 carbon atoms present. eg. C7H 14O
3.According to the number of sugar unit present:
a. Monosaccharides: Simple units of carbohydrates (polyhydroxyaldehydes or
polyhydroxyketones) that cannot be broken into simpler carbohydrates upon
hydrolysis. eg. glucose, fructose, galactose
b. Oligosaccharides: Made of 2 to 10 units of monosaccharides or simple sugar.
i. Disaccharides: Made of 2 units of monosaccharides or simple sugar.
sugars remain attached with each other by Glycosidic linkage. eg. sucrose
ii.Trisaccharides: Made of 3 units of monosaccharides or simple sugar.
c. Polysaccharides: Made of more than 10 units of monosaccharides or simple
sugar. eg. cellulose
N.B. All naturally occuring carbohydrates are generally dextrorotatory isomers or
The most important naturally occuring monosaccharides are pentoses and hexoses.
Of these glucose and fructose are the most important and typical.
1.Caloriefic value of carbohydrates is 4.1K.Cal/gm i.e. burning of 1 gm of
carbohydrates yields 4.1K.Cal of heat.
2.Carbohydrates act as the main component of living body.
3.It helps in general growth and repairing of body.
4.Carbohydrates stores as glycogen in the addipose tissue of muscle.
5.It helps in protein and lipid metabolism.