BIOMOLECULES

BIOMOLECULES

Carbohydrate

Amino acid &

Protein

Enzyme
Biomolecules
Vitamin

Nucleic Acid

Hormone
CARBOHYDRATES
 CARBOHYDRATES

 Carbohydrates:

Chemically, the carbohydrates may be defined as optically active

polyhydroxy aldehydes or ketones or the compounds which produce
such units on hydrolysis.

Carbohydrates are also called saccharides.

Carbohydrates, which are sweet in taste, are also called sugars.

First classification

Mannose
  Types of Carbohydrates:

Monosaccharides : Simplest carbohydrate

Oligosaccharides : Which consists two to ten monosaccharides

If two units then it is called as Disaccharides
If three units then it is called as Trisaccharides

Polysaccharides : Which consists more than ten monosaccharides

Monosaccharides can not be
broken-down hence not hydrolysed

Disaccharides can be
broken-down hence hydrolysed

Polysaccharides can be
broken-down hence hydrolysed
 Second classification

Give Fehlings & Tollens test Not Give Fehlings & Tollens test

Contain free aldehyde or keto group Not Contain free aldehyde or keto group
Or contain hemiacetal linkage Or Not contain hemiacetal linkage

Example:
Example:
1. All monosaccharides
Ex: glucose, fructose etc 1. All Polysaccharides
2. All disaccharide ( except sucrose) 2. Sucrose
Ex Maltose and lactose etc

 All reducing sugar show mutarotation.

Monosaccharides
NCERT Glucose Fructose
Monosaccharides :

A simplest carbohydrate that can not be further hydrolysed is called

monosaccharides.

If a monosaccharides contain:
(a) an aldehyde group- Aldose
(b) a keto group- Ketose

If a monosaccharides contain:

(i) Three carbons - Aldotriose Ketotriose

(ii) Four carbons - Aldotetrose Ketotetrose
(iii) Five carbons - Aldopentose Ketopentose
(iv) Six carbons - Aldohexose Ketohexose
Glucose Other name: Dextrose Grape sugar

D-(+)-Glucose

(Relative configuration) (dextrorotatory) means rotation of PPL light

 (Aldhexose) (Aldhexose) (Aldhexose)

D-Mannose D-Glucose D-Galactose

Epimers: “Epimers are diastereomers that differ in configuration at

only one chiral center.”
Note :
(1) D-Glucose & D-Mannose are C-2 Epimer
(2) D-Glucose & D-Galactose are C-4 Epimer
“All epimers are diastereomers”
 ?
Q. D-Erythrose and D-Threose are ….…. Epimers.

D-Erythrose D-Threose

Ans. D-Erythrose and D-Threose are C-2 Epimers.

 (NEET-II 2016)

D-Threose L-Threose
Enantiomers
 CHEMICAL REACTIONS OF GLUCOSE
Chemical reactions of glucose :-
Oxidation:

Fructose does
not react with
Br2 water.
 CHEMICAL REACTIONS OF GLUCOSE

Reduction:
 CHEMICAL REACTIONS OF GLUCOSE
Reaction with hydroxyl amine and hydrogen cyanide:
 CHEMICAL REACTIONS OF GLUCOSE

Acetylation:
 CHEMICAL REACTIONS OF GLUCOSE
Important point about Glucose:

Reason: due to cyclic structure of glucose,

these reagents can’t break ring.

 Pentaacetate of glucose does not react with hydroxylamine.

 CYCLIC STRUCTURE OF GLUCOSE

α-D-(+)-Glucose D-(+)- Glucose β-D-(+)-Glucose

m.p. 419 K m.p. 423 K

Anomer: α-Glucose and β-Glucose are diastereomers that differ in configuration at

functional group carbon.” Hence α-Glucose and β-Glucose both are Anomer to
each other.
 Haworth Structure of Glucose

Pyran

Pyranose ring
(Haworth structure)
α-D-(+)-Glucopyranose β-D-(+)-Glucopyranose
Mutarotation:

The α-Glucose and β-Glucose have different specific rotations.

When either is dissolved in water, their specific rotation changes to
reach a certain fixed value (+52.5°). This is called Mutarotation.

 All reducing sugar show mutarotation.

Q. Which of the following does not exhibit the phenomenon of
mutarotation ? (AIPMT 2010)

(1) (-) Fructose

(2) (+) Sucrose
(3) (+) Lactose
(4) (+) Maltose

 All reducing sugar show mutarotation.

 CYCLIC STRUCTURE OF FRUCTOSE

Ketohexose: Fructose Laevulose (laevorotatory)

α-D-(-)-Fructose D-(-)- Fructose β-D-(-)-Fructose

 Anomeric carbon means FG carbon

Anomeric carbon in Glucose : C1
Anomeric carbon in Fructose : C2
 Haworth Structure of Fructose

Furan

Furanose ring
(Haworth structure)
α-D-(-)-Fructofuranose β-D-(-)-Fructofuranose
In alkaline solution, fructose change into glucose & fructose and vice versa

This conversion is called as

Lobry de Bruyn van Eikenstein rearrangement

 Lobry de Bruyn van Eikenstein rearrangement

 Alkaline solution of fructose contain glucose, fructose and mannose.

 Fructose reduces Tollen’s reagent due to :- (AIPMT Main 2010)

Enolisation of fructose followed by conversion to aldehyde by base
Remember = Fructose don’t have aldehyde or hemiacetal group but still reducing sugar
due to change in glucose or mannose.
 OSAZONE

(Phenyl
hydrazine)

(D-Glucose/D-Mannose) (Osazone)

Important = During osazone formation top two carbons participate hence those molecules
having same configuration at C-3, C-4, C-5 will give same osazone.
Q. Which of the following carbohydrate give same osazone :
(1) D-Glucose (2) D-Mannose (3) D-Fructose (4) D-Galactose

D-Glucose D-Mannose D-Fructose D-Galactose

Explanation = During osazone formation top two carbons participate hence those molecules
having same configuration at C-3, C-4, C-5 will give same osazone.

Hence D-Glucose , D-Mannose , D-Fructose give same osazone.

Disaccharides
Sucrose
Maltose

Lactose
 OLIGOSACCHARIDES
Oligosaccharides:
 Carbohydrates that yield two to ten monosaccharide units, on
hydrolysis, are called oligosaccharides.
 Example disaccharides, trisaccharides, tetrasaccharides, etc.,
depending upon the number of monosaccharides, they provide on
hydrolysis.

Carbohydrates that yield two monosaccharide units, on hydrolysis.

Example : sucrose, maltose, lactose
 Sucrose Maltose Lactose

Glucose Fructose Glucose Glucose Galactose Glucose

α- Pyranose β- Furanose α - Pyranose α - Pyranose β - Pyranose β - Pyranose

1,2- glycosidic link 1,4- glycosidic link 1,4- glycosidic link

(NEET-2020)
 DISACCHARIDES

Invert Sugar

“Hydrolysis of sucrose brings about a change in the sign of rotation,

from dextro (+) to laevo ( ) and the product is named as invert sugar.”
 Maltose

 Anomeric carbon means FG carbon

Anomeric carbon in Glucose : C1
Anomeric carbon in Fructose : C2
α-D-Glucose α-D-Glucose

Reducing sugar

C1 of α-D- Glucose + C4 of α-D- Glucose (AIIMS 2011, 2014)

 Lactose

β -D-Galactose β -D-Glucose

Reducing sugar

C1 of β -D- Galactose + C4 of β -D- Glucose

 Sucrose:

 Anomeric carbon means FG carbon

Anomeric carbon in Glucose : C1
Anomeric carbon in Fructose : C2 α-D-Glucose β -D-Fructose

Non reducing sugar

Glycosidic
linkage

C1 of α-D- Glucose + C2 of β -D- Fructose (NEET-2020)

Q Which of the following is non-reducing sugar :-
 POLYSACCHARIDES
Polysaccharides :
Carbohydrates which yield a large number of monosaccharide units on
hydrolysis are called polysaccharides. Examples are starch, cellulose,
glycogen, gums, etc.
Polysaccharides are non-reducing and not sweet in taste (non-sugars).

Starch (Polymer of α-D-glucose)

Amylose Amylopectin
• α-D-(+)-glucose • α-D-(+)-glucose
• Water soluble • Water insoluble
• 15-20 % of starch • 80-85 % of starch
• Long unbranched chain • Branched chain polymer
• C1-C4 glycosidic linkage • C1-C4 glycosidic linkage
C1-C6 glycosidic linkage
 POLYSACCHARIDES

Amylose

Amylopectin
Q. The difference between amylose and amylopectin is :-
NEET (UG) 2018
(1) Amylopectin have 1→ 4 α-linkage and 1→ 6 β-linkage
(2) Amylose have 1→ 4 β-linkage and 1→ 6 β -linkage
(3) Amylopectin have 1→ 4 α-linkage and 1→ 6 α-linkage
(4) Amylose is made up of glucose and galactose
 POLYSACCHARIDES
Cellulose Glycogen (Animal Starch)
• Polymer of β-D-glucose • Polymer of β-D-glucose
alpha-D-glucose
• C1-C4 glycosidic linkage • Similar to amylopectin but more
branched
• Most abundant organic substance • Present in liver, muscle and brain,
in plant kingdom also found in yeast and fungi

(Cellulose)
 AMINO ACIDS AND PROTEINS
Amino Acids:
Amino acids contain amino (–NH2) and carboxyl (–COOH) functional
group.
There are 20 amino acids (α- amino acids) which are obtained on
hydrolysis of proteins.
Most of them have 1o amino group (-NH2), however proline has 2o
amino group.

α- Amino acid

(Proline)
 AMINO ACIDS AND PROTEINS
Amino acids are usually colourless, crystalline solids. These are water-soluble,
high melting solids and behave like salts (Zwitter ion) rather than simple
amines or carboxylic acids.

Isoelectric point (pI) = The pH

at which the amino acid exists
(Zwitter ion) only as a dipolar ion with net
Neutral dipolar ion charge zero (does not migrate
(Amphoteric behaviour) to either electrode).

Most naturally occurring amino acids have L-configuration.

(Enantiomers)

D-Alanine L-Alanine
 AMINO ACIDS AND PROTEINS
Classification of Amino acids:
(1) On the basis of requirement:-
(a) Essential Amino acids :-
Amino acids which can not be synthesised in human body so must
be taken through diet, are known as essential amino acids.
(b) Non-essential Amino acids :-
Amino acids which can be synthesised in body, are known as non-
essential amino acids.

(c) Semi-essential Amino acids :-

Amino acids which can be synthesised in body but required in diet
during growing stages, are known as semi-essential amino acids.
 AMINO ACIDS AND PROTEINS

Essential Amino Acid Non-essential Amino Acid

1. Threonine (Thr) 1. Alanine (Ala)
2. Tryptophan (Trp) 2. Aspartic acid (Asp)
3. Histidine (His) Semi-essential 3. Asparagine (Asn)
Amino Acid
4. Arginine (Arg) 4. Glycine (Gly)
5. Lysine (Lys) 5. Glutamic acid (Glu)
6. Leucine (Leu) 6. Glutamine (Gln)
7. Methionine (Met) 7. Cysteine (Cys)
8. Valine (Val) 8. Tyrosine (Tyr)
9. Isoleucine (Ile) 9. Serine (Ser)
10. Phenylalanine (Phe) 10. Proline (Pro)
 AMINO ACIDS AND PROTEINS

Classification of Amino acids:

(2) On the basis of chemical nature:-

(a) Neutral Amino acids: α- Amino acid

No. of –COOH groups = No. of –NH2 groups

(Glycine)
(Alanine)

(Phenylalanine) (Valine)
 AMINO ACIDS AND PROTEINS
(b) Acidic Amino acids:
No. of –COOH groups > No. of –NH2 or basic groups

(Aspartic acid) (Glutamic acid)

(c) Basic Amino acids:

No. of –COOH groups < No. of –NH2 or basic groups

(Lysine) (Arginine) (Histidine)

Q. Which of the following is most basic amino acid ? (AIIMS 2016)
(1) Lysine (Lys) (2) Histidine (His)
(3) Arginine (Arg) (4) Aspartic acid (Asp)

Basic Strength order :- Arginine > Lysine > Histidine > Aspartic acid
 AMINO ACIDS AND PROTEINS
Proteins:
Proteins are the polymers of α-amino acids and they are connected to each
other by peptide bond or peptide linkage (Amide linkage).

Glycine Alanine
(Gly) (Ala)

Peptide linkage
Glycylalanine (Gly-Ala)
(Dipeptide)
 AMINO ACIDS AND PROTEINS

Q. The number of peptide bonds in a tripeptide is :

(1) Three (2) Four (3) Two (4) One

 A tripeptide contains three amino acids linked by two peptide linkages.

Gly-Ala-Phe
 AMINO ACIDS AND PROTEINS

 Some Important Points about Proteins :- NCERT

(1) Proteins may have one or more polypeptide chains. Each polypeptide chain
in a protein has amino acids linked with each other in a specific sequence, this
sequence of amino acid called primary structure of that protein..

(2) Secondary structure of proteins are found to exist in two different types of
structures namely α-helix and β -pleated sheet structure (due to hydrogen
bonding between >C=O and NH—groups of the peptide bond).

(3) Fibrous proteins are generally insoluble in water. Some common examples
are myosin (present in muscles) and keratin (present in hair, wool, silk), etc.

(4) Globular protein are usually soluble in water. Some common examples
are Insulin and albumins.
 AMINO ACIDS AND PROTEINS

 Some Important Points about Proteins :- NCERT

(4) Insulin has well defined conformation of a protein which contains

51 amino acids.

(5) Denaturation of protein causes loss of secondary and tertiary structures

of protein but primary structure remains intact.
 ENZYMES

 Some Important Points about Enzymes:- NCERT

(1) Enzymes (biocatalysts) helps in coordination of various chemical

reactions in living organisms like digestion of food, absorption of appropriate
molecules and ultimately production of energy.

(2) Almost all the enzymes are globular proteins.

(3) They are generally named after the compound or class of compounds
upon which they work.
 VITAMINS

 Some Important Points about Vitamins:- NCERT

(1) Vitamins are organic compounds required in the diet in small amounts to
perform specific biological functions for normal maintenance of optimum
growth and health of the organism.

(2) Fat soluble vitamins: Vitamins which are soluble in fat and oils but
insoluble in water. Examples A, D, E and K. They are stored in liver and
adipose (fat storing) tissues.

(3) Water soluble vitamins: B group vitamins and vitamin C are soluble in
water. They are readily excreted in urine and cannot be stored (except
vitamin B12) in our body.
 NUCLEIC ACIDS

 Nucleic Acids :-
Nucleic acids are long chain polymers of nucleotides, so they are also called
polynucleotides.
These are mainly of two types, the deoxyribonucleic acid (DNA) & ribonucleic
acid (RNA).
Nucleotide Base + Sugar + Phosphate

Nucleoside Base + Sugar

 NUCLEIC ACIDS
Nitrogenous Bases:
(a) Purine Nitrogenous Bases:

Adenine (A) Guanine (G)

(b) Pyrimidine Nitrogenous Bases:

Cytosine (C) Uracil (U) Thymine (T)

 NUCLEIC ACIDS
Q. Which of the following bases is not present in DNA? NCERT Exemplar
(1) Adenine (2) Thymine
DNA- A,G,C,T
(3) Cytosine (4) Uracil RNA- A,G,C,U
Sugar:

D-Ribose D-2-Deoxyribose
(RNA) (DNA)

 RNA and DNA are chiral molecules, their chirality is due to D-sugar
component. (AIPMT 2007)
 HORMONES
 Some Important Points about Hormones:- NCERT
(1) Peptide Hormone: Ex. Insulin, endorphins, glucagon, etc.
(2) Steroidal Hormone: Ex. Estrogens, androgens, etc.
(3) Amino acid derivative Hormone: Ex. Epinephrine, norepinephrine, etc.
Q. Which of the following hormone contains iodine ? (AIPMT 2009)
(1) Insulin (2) Testosterone
(3) Adrenaline (4) Thyroxine

 Thyroxine hormone produced in the thyroid gland is an iodinated

derivative of amino acid tyrosine.
 Thyroxine is an amine hormone. (AIPMT 2008)
 BIOMOLECULES
Test of Carbohydrates:
Molisch test:
This test is used for detection of all types of carbohydrates, i.e.,
monosaccharides, disaccharides and polysaccharides.
Molisch reagent (1% alcoholic solution of - naphthol) is added to the
aqueous solution of a carbohydrate followed by conc. H2SO4 along the sides of
the test tube. A violet ring is formed at the junction of the two layers.
 BIOMOLECULES
Test of Proteins:
Biuret test:
An alkaline solution of a protein when treated with a few drops of 1% CuSO4
solution, produces a violet colouration. The colour is due to the formation of
a coordination complex of Cu+2 with the peptide linkages. This test is used
for detecting the presence of peptide bonds.
 BIOMOLECULES
Q. Which of the following is a test of proteins ?
(1) Molisch’s test
(2) Biuret test
(3) Seliwanoff’s test
(4) Barfoed’s test

Molisch’s test : All carbohydrate give this test

Biuret test : This test is given by protein (used for detecting the presence of
peptide bonds).
Seliwanoff’s test : Ketohexose (fructose) and sucrose give this test.
Barfoed’s test : Only monosaccharides give this test.