3. What are Biomolecules?
Every living matter is composed of mainly six elements - carbon,
hydrogen, oxygen, nitrogen, phosphorus and sulfur.
Other elements may also include in living matter functionalities like-
Ca, K, Na, Cl, Mg, Fe, Cu, Co, l, Zn, F, Mo and Se.
These elements form molecules with each other and many molecules
form macromolecules with each others.
These molecules and macromolecules in living matters are termed as
Biomolecules (Chemical entities for life).
6. Introduction
Carbohydrates are the most abundant biomolecules on earth.
Carbohydrates are primarily produced by plants and form a very large
group of naturally occurring organic compounds.
Carbohydrates are the rich source of energy for living organisms.
Carbohydrates are polyhydroxy aldehydes or ketones, or substances that
yield such compounds on hydrolysis.
Carbohydrates have empirical formula (CH2O)n ; some also contains
nitrogen, phosphorous, or sulfur.
7. Classification of Carbohydrates
There are major size of classes of carbohydrates;
o Monosaccharides,
o Oligosaccharides, and
o Polysaccharides
• The word “saccharide” is derived form the Greek “sakcharon” , meaning
“sugar”.
8. 1. Monosaccharides
Monosaccharides (Greek : mono-one) are the simplest group of
carbohydrates and are often referred to as simple sugars.
They have the general formula Cn(H20)n, and they cannot be further
hydrolyzed.
Monosaccharides are further classified on the basis of number of carbon
atoms present in the molecule. E.g.
9.
10. 2. Oligosaccharides
Oligosaccharides (Creek: oligo-few) contain 2-1O monosaccharide
molecules which are liberated on hydrolysis.
Based on the number of monosaccharide units present, the
oligosaccharides are further subdivided to disaccharides, trisaccharides
etc.
a) Disaccharides - Which yield two monosaccharides’ molecules on hydrolysis.
Which have molecular formula is C12H22O11. e.g., Sucrose, maltose etc.
11. b). Trisaccharides - Which yield three monosaccharides’ molecules on
hydrolysis and have molecular formula is C18H32O16.
c). Tetrasaccharides - Which yield four monosaccharides molecules
on hydrolysis and have molecular formula is C22H42O21
12.
13. 2. Polysaccharides
Polysacchari6ls (Creek: poly-many) are polymers of monosaccharide units
with high molecular weight (up to a million).
They are usually tasteless (non-sugars) and form colloids with water.
The polysaccharides are of two types - homopolysaccharides and
heteropolysaccharide.
14.
15. Elucidation of chemical nature of carbohydrates
Glucose………
Glucose is an aldohexose and is also known
as dextrose.
It is the monomer of many of the larger
carbohydrates, namely starch, cellulose.
It is probably the most abundant organic
compound on earth.
On the basis of glucose properties and
structure, we can elucidate the chemical
nature of carbohydrates.
16. 1. Oxidation
Glucose gets oxidized to six carbon carboxylic acid (gluconic acid) on
reaction with a mild oxidizing agent like bromine water.
This indicates that the carbonyl group is present as an aldehydic group.
17. 1. Oxidation
On oxidation with strong oxidizing agents like nitric acid, glucose as well
as gluconic acid both yield a dicarboxylic acid, saccharic acid.
This indicates the presence of a primary alcoholic (–OH) group in glucose.
18. 2. Reduction
On the treatment with reducing agents like sodium amalgam, aldehyde or
ketone group reduces to corresponding alcohols.
C
O H
C
C
C
C
CH2OH
HO
H
H
H
H
H
H
H
D-glucose
+ HgNa
Reduction
CH
HO H
C
C
C
C
CH2OH
HO
H
H
H
H
H
H
H
D-sorbitol
19. 3. Acetylation
Acetylation of glucose with acetic anhydride gives glucose pentaacetate
which confirms the presence of five –OH groups.
20. 4. Dehydration (Molisch Reagent Test)
on treatment with H2SO4, carbohydrates eliminate 3 molecules of water
and form furfurals.
C
O H
C
C
C
C
CH2OH
HO
H
H
H
H
H
H
H
D-glucose
Conc.
C
O H
C
C
C
C
CH2OH
H
H
Furfural
O
H2SO4
-3H2O
21. HYGIA GROUP OF INSTITUTIONS
GHAILA ROAD, GAAZIPUR BALRAM,
FAIZULLAHGANJ, LUCKNOW
