1.  Most abundant organic molecule in nature.
 Literally means ‘hydrates of carbon’ i.e. (C.H2O)n.
 When n is 3 it satisfies the definition of hydrates of
carbon.
 Several non-carbohydrates also satisfies the
definition of hydrates of carbon i.e. acetic
acid(C2H4O3), lactic acid (C3H6O3).
 Some of the genuine carbohydrates where n is
above 3 do not satisfy the general formula.
 Hence Carbohydrates cannot be always considered
as hydrates of carbon.

2. Carbohydrates may be
defined as polyhydroxy-
aldehydes or Ketones or
compounds which produce
them on hydrolysis.
The term ‘sugar’ is applied for carbohydrates
soluble in water and sweet in taste.

3. The most abundant dietary source of energy
(4cal/g) for all organism.
Precursors for many organic compounds
(fats, amino acids etc).
Carbohydrates ( as glycoprotein and
glycolipids) participate in the structure of cell
membranes and cellular functions such as cell
growth etc.

4. Structural components of many organisms like
the fiber (cellulose) of plants, exoskeleton of
some insects and the cell wall of
microorganisms.
Also serve as the storage form of
energy(glycogen) to meet the immediate
energy demands of the body.
They are utilized as raw materials for several
industries e.g. paper, plastic, textile alcohol
etc.

5. Carbohydrates are often referred to as
saccharides .
Broadly classified into 3 groups.
1. Monosaccharides
2. Oligosaccharides
3. polysaccharides

6.  Simplest form of carbohydrates and are
referred as simple sugars.
 Have general formula Cn(H2O)n.
 They cannot be further hydrolyzed.
 Further classified based on the functional
groups and the number of carbon atoms.
 Based on the functional groups they are
classified as
1. Aldoses: Aldehyde as functional group
2. Ketoses: ketone as functional group

7.  Based on the number of carbon atoms they are
classified as
1. Trioses: 3 carbon
2. Tetroses: 4 carbon
3. Pentoses: 5 carbon
4. Hexoses: 6 carbon
5. Heptoses: 7 carbon
These terms are used along with functional
groups while naming monosaccharides.
e.g. Glucose is Aldohexose and Fructose is
Ketohexose.

11.  Contains 2-10 monosaccharide molecules
which are liberated on hydrolysis.
 Based on the number of monosaccharides
units present they are subdivided as.
1. Disaccharides :
 On hydrolysis produce 2 molecules of the
same or different monosaccharide.
I. Maltose Glucose + Glucose
II. Sucrose Glucose + Fructose
III. Lactose Glucose + Galactose

12. 2. Trisaccharides :
 Contains 3 monosaccharide units .
Raffinose Fructose+Galactose+Glucose
3. Tetrasaccharides :
 Contains 4 monosaccharide units.
Stachyose 2(Galactose)+Glucose+Fructose
4. Pentasaccharides :
 Contains 5 monosaccharide units.
Verbascose 3(Galactose)+Glucoce+Fructose

13.  They are polymers of monosaccharides units
with high molecular weights(up to million).
 They are usually tasteless(non-sugars) and
form colloids with water.
 They are of 2 types.
1. Homopolysaccharides (Homoglycans):
 Contain monosaccharide units of a single
type. E.g. Starch,Glycogen,Inulin,Cellulose.
2. Heteropolysaccharides (Heteroglycans):
 Possess 2 or more different types of
monosaccharides units or their derivatives.
E.g. heparin, chondroitin sulfate.

14. 1) Asymmetric Carbon:
 When it is attached to 4 different atoms or
groups.
 The number of asymmetric carbons(n)
determines the possible isomers of a given
compound which is equal to 2n .
 Glucose contains 4 asymmetric carbons and
thus has 16 isomers.

15. 2) Stereoisomers:
 Stereoisomers are the compounds that have
same structural formulae but differ in their
spatial arrangement.
 Stereoisomerism is an important character of
monosaccharides.
 Glyceraldehyde has one asymmetric carbon
atom and hence exists as 2 Stereoisomers.
 Glyceraldehyde has been chosen as reference
carbohydrate to represent the structure of
all other carbohydrate.

17. 3) D and L isomers:
 D and L isomers are mirror images of each
other.
 The spatial arrangement of –H and –OH
groups on the carbon atom that is adjacent
to the terminal primary alcohol carbon
determines whether the sugar is D or L type.
 If the –OH group is on the right side the sugar
is of D series and if on the left side it belongs
to L series.

18. The naturally occurring monosaccharide
in mammalian tissues is mostly of D
series.
The enzyme machinery of cells is specific
to metabolize D series of
monosaccharide.

19. 4) Optical activity of sugars:
 Optical activity is characteristic of
compounds with Asymmetric carbon atom.
 When a beam of polarised light is passed
through a solution of an optical isomer it will
rotate either to the right or left.
 When it rotates to right it is called
Dextrorotatory and when it rotates to left it
is called Levorotatory.

20. 5) Racemic mixture:
 When D and L isomers are present in equal
concentration it is known as Racemic mixture
or DL mixture.
 Racemic mixture does not exhibit any
optical activity since the Dextro and
Levorotatory activities cancel each other .
 Optical activity of Racemix mixture is Zero.

21. 6) Epimers:
 If 2 monosaccharides differ from each other
in their configuration around a single specific
carbon (other than Anomeric carbon) they
are referred as Epimers of each others.
 Glucose and Galactose are Epimers with
regards to carbon 4 (C4 Epimers).
 Glucose and mannose are Epimers with
regards to Carbon 2 ( C2 Epimers).

22. •The interconversion of Epimers(glucose
to Galactose and vice versa) is known as
Epimerization.
•The enzyme which catalyze this
reactions are called as Epimerases.