Page 2 of 29
2. On the basis of molecular structure and hydrolysis, carbohydrates have been classified into the following three groups-
(i) Monosaccharides
(ii) Oligosaccharides
(iii) Polysaccharides
(1) Monosaccharides: The carbohydrates which do no hydrolyse, are called monosaccharide. They are itself a polyhydroxy carbonyl compounds. They are also called as simple sugars. E.g. glucose, fructose, mannose, ribose etc.
(ii) Oligosaccharides: The carbohydrates which on hydrolysis give two to ten monosaccharide units, are called oligosaccharides. The monosaccharide units obtained on hydrolysis may be same or different.
They are classified on the basis of number or monosaccharide units obtained on hydrolysis-
(A) Disaccharides: If two monosaccharide units are obtained on hydrolysis then it is called disaccharides. The formula of disaccharides is C12H22O11. E.g. Sucrose, Lactose and Maltose.
(B) Trisaccharides: If three monosaccharide units are obtained on hydrolysis then it is called trisaccharides. The formula of trisaccharides is C18H32016. E.g. Raffinose.
(C) Tetrasaccharides: If four monosaccharide units are obtained on hydrolysis then it is called tetrasaccharides. The formula of tetrasaccharides is C24H42021. E.g. stachyose.
(iii) Polysaccharides: The carbohydrates which on hydrolysis give more than ten monosaccharide units are called polysaccharides. Their molecular mass is very high and uncertain. Thus the number of monosaccharide units present in their molecules is also not certain. The general molecular formula, of polysaccharide starch and cellulose found in nature, is (C6H10O5).
On the basis of types of constituents units polysaccharides can further classified into two parts-
(A) Homopolysaccharides: Those polysaccharides which have similar type of constituents units are termed as homopolysaccharides. E.g. Starch and Cellulose.
(B) Heteropolysaccharides: Those polysaccharides which have different type of constituents units are termed as heteropolysaccharides. E.g. Heparin and gamma globulin.
# Nomenclature and classification of monosaccharides: The name of every simple sugars ends with
'ose'. If aldehyde group is present in the monosaccharide then it is called aldose and if ketone group is present then it is called ketose. The number of carbon atoms present in the molecule is expressed as prefix. E.g. glucose is an aldose and fructose is a ketose and six carbon atoms are present in both of them. Thus glucose is an aldohexose and fructose is a ketohexose.
# Structure of Monosaccharides:
1. Structure of Pentose and Hexose: All carbohydrates are either monosaccharides or give monosaccharides on hydrolysis. Among monosaccharides pentose and hexose are most important and widely found. Their general structures are as follows:
BHARDWAJ COACHING CLASSES 595-VINOBA BASTI, SRI GANGANAGAR #94145-06101, 97997-29101
(HARSH BHARDWAJ)
0 Comments