Quick revision and question

DAY THIRTY FOUR

Biomolecules
Learning & Revision for the Day

u Carbohydrates u Enzymes u Vitamins
u Proteins u Hormones u Nucleic Acids


Biomolecules are the complex, lifeless organic substances. These build up living
organisms and are required for their growth and maintenance. Carbohydrates, proteins,
nucleic acids, lipids etc., are the examples of biomolecules. Vitamins and mineral salts
also play an important role in functions of organisms.

Carbohydrates
Carbohydrates are optically active polyhydroxy aldehydes or ketones or compounds which
produce such units on hydrolysis.


Classification of Carbohydrates
Carbohydrates are also known as saccharides and classified according to their behaviour

Carbohydrates
Depending upon the units
produced after hydrolysis

Monosaccharides Oligosaccharides Polysaccharides
Named systematically (Oligos-few) Yield 2-9 Hydrolysed to
according to the monosaccharides more than
number of on hydrolysis. 9 monosaccharides.
carbon atoms they contain.
Crystalline solids, soluble in water and Amorphous solids, insoluble in
sweet in taste and collectively called water and tasteless and thus are
sugars. called non-sugars.
Except sucrose, all are reducing sugars. All polysaccharides are
non-reducing sugars.

towards hydrolysis.
l
D, L - configuration ‘D’ or ‘L’ letter before the name of any compound indicates the
relative configuration of particular stereoisomer in relation to two enantiomeric forms
of glyceraldehyde.
CHO D-means CHO
—OH on right
H OH HO H
CH2OH L-means
CH 2OH
D-glyceraldehyde —OH on left

, l
The monosaccharides having configuration identical to Following reactions give evidences in favour of open chain
D-glyceraldehyde are assigned D-configuration whereas structure of glucose :
those having configuration identical to L-glyceraldehyde CHO
are assigned L-configuration. | HI, ∆
(i) (CHOH)4 → CH3 — ( CH2— )4 CH3
| n -hexane
Monosaccharides CH2OH
A carbohydrate that cannot be hydrolysed further to give
CH O CH NOH
simpler unit of polyhydroxy aldehyde or ketone is called
N H2 OH
monosaccharide. (ii) (CHOH)4 (CHOH)4
_
H2O
If a monosaccharide contains an aldehydic group, it is
CH2 OH CH2OH
known as an aldose and if it contains a keto group, it is Glucose oxime
known as a ketose. OH
e.g. glucose, fructose, galactose, are hexose, while ribose and CHO CH
arabinose are pentose. | | CN
(iii) (CHOH)4 →
HCN
(CHOH )4
| |
1. Glucose (C6H12O6 ) CH2OH CH2 —OH
Glucose cyanohydrin
It occurs freely in nature as well as in the combined form. It
is present in sweet fruits and honey. Ripe grapes also CHO COOH
contains glucose in large amount. | Br2 / water
|
(iv) (CHOH)4 → (CHOH)4
l
It is an aldohexose and also known as dextrose (grape | |
sugar). CH2OH CH2OH
l
It is prepared as follows Gluconic acid

H
+ CHO CHO
C 12H22O 11 + H2O → C 6H 12O 6 + C 6H 12O 6 | (CH3CO) 2O
|
Sucrose or invertase
Glucose Fructose (v) (CHOH)4 → (CHOCOCH3 )4
+ |  O
H
(C 6H 10O 5) n + nH2O → nC 6H 12O 6 CH2OH  ||
Starch
393 K, 2 -3 atm Glucose CH2 —O—C — C H3
Two types of structure have been suggested for glucose Glucose pentaacetate
molecule.
CHO COOH COOH
Open Chain Structure | HNO3
| O xidation
|
(vi) (CHOH)4 → (CHOH)4 ← (CHOH)4
Oxidation |
The open chain structure of glucose can be represented by | |
using Fisher projection. CH2OH COOH CH2 —OH
Glucaric acid or G luconic acid
O saccharic acid

1 a 1
H C OH H C CHO CH N⋅NHPh
H
2
OH O H
2
OH | |
(vii) –H2O
3 3 (CHOH)4 + H2N⋅NH⋅C6H5 H—C —OH
HO H HO H |
4 4 |
H OH H OH CH2OH (CHOH)3
5 5
H H OH |
6 6 CH2OH
CH2OH CH2—OH Glucose
α-D-(+)-glucose Glucose phenylhydrazone


1 β C H N⋅NHPh
HO C H | 2H2N⋅NHPh
2 PhNH2 + NH3 + C N⋅NHPh
H OH O |
3 (CHOH)3
HO H
4 |
H OH
5 CH2OH
H Glucosazone
6
CH2OH Glycolysis is the anaerobic degradation of glucose into two
β-D-(+)-glucose molecules of pyruvic acid.