2. Introduction
• Carbohydrates are most abundant organic
molecules in nature.
• They are primarily composed of the elements
1. Carbon
2. Hydrogen
3. Oxygen
• Carbohydrates may be defined as polyhydroxy
aldehydes or ketones or compounds which
produce them on hydrolysis.
3. Functions of carbohydrates
• The term ‘sugar’ is applied to carbohydrates
soluble in water and sweet to taste.
• Carbohydrates are precursors for many
organic compounds.
• They are most abundant dietary source of
energy (4 Cal/g)for all organisms.
4. Continued ………………
• Carbohydrates also serve as storage form of
energy (glycogen) to meet the immediate
energy demands of the body.
• Carbohydrates participate in the structure of
cell membrane and cellular function such as
cell growth, adhesion and fertilization , such
as
1. Glycoprotein
2. glycolipids
5. Classification of carbohydrates
• Carbohydrates are often referred to as
saccharides.
• They are broadly classified into 3 groups.
1. Monosaccharides
2. Oligosaccharides
3. Polysaccharides
• This categorization is based on the number
of sugar unit.
6. Monosaccharide
• Monosaccharides are the simplest group of
carbohydrates and often referred to as simple
sugars.
• They cannot be further hydrolysed.
• Monosaccharides further classified:-
1. Based on their functional group
2. Based on the number of carbon atoms
7. Based on their functional group
• Aldoses : when the functional group in
monosaccharide is aldehyde, they are known
as aldoses e.g. glyceraldehyde, glucose.
• Ketoses : when the functional group is a keto
or carbonyl group, they are referred to as
ketoses e.g. dihydroxyacetone, fructose.
8. Based on their no. of carbon atoms
1. Trioses(3C)
2. Tetroses(4C)
3. Pentoses(5C)
4. Hexoses(6C)
5. Heptoses (7C)
• The term along with functional groups are used
while naming monosaccharides.
• For instance glucose is a aldohexose while
fructose is a ketohexose.
9. Oligosaccharide
• Oligosahharide contain 2-10 monosaccharide
molecules which are liberated on hydrolysis.
• Based on number of monosachheride units
present , the oligosaccharides are subdivided
to disaccharides , trisaccharides etc
10. Polysaccharides
• Polysaccahrides are polymers of
monosaccharides units with high molecular
weight .
• They are tasteless and form colloids with
water.
• Polysaccharides are two types
1. Homopolysaccharides
2. heteropolysaccahrides
