BIOMOLECULES

CHAPTER – 14

FIITJEE – DPS MIS

DOHA, QATAR
 CONTENTS
1. Introduction

2. Carbohydrates

3. Proteins

4. Enzymes

5. Vitamins

6. Nucleic Acids
 INTRODUCTION

All living systems undergoes changes each and every second through various Biological and
Chemical reactions. Such changes/ reactions are known as Biochemical Reactions and the
science that deals with such changes is Biochemistry.
In terms of chemistry, the compounds that brings about all these changes can be classified into
different types based on chemical structures of the molecules such as Carbohydrates, Fats,
Lipids, Proteins, Amino acids, Enzymes, Vitamins and Minerals, Nucleic Acids etc.
Out of many such compounds, the following few compounds shall be seen:
Carbohydrates – Energy producing Chemicals
Proteins – Body Building/ Repairing Chemicals
Enzymes – Biological Catalysts
Vitamins – Key Functional Chemicals
Nucleic Acids – Hereditary Repeating Chemicals

CARBOHYDRATES

In early times, Carbohydrates are considered as the “Molecules in which most of the Carbon
atoms formally having a molecule of water attached in the form of H and OH, for hydrated
Carbon”. The general chemical formulae of Carbohydrates is Cx(H2O)y.
Though Formaldehyde and Acetic acid fits into this specific chemical formula, are actually not
Carbohydrates.
Hence, chemically Carbohydrates are “Optically Active Polyhydroxy Aldehydes or Ketones
or substances that hydrolyze to yield Polyhydroxy Aldehydes or Ketones”. Carbohydrates
generally exist in Hemi – Acetals and Acetals form and are also called as Saccharides.
BASED ON NUMBER OF UNITS PRODUCED ON HYDROLYSIS
1. Monosaccharides: The carbohydrates, those CANNOT be further hydrolysed into
simpler carbohydrates are Monosaccharides.
Example: Glucose and Fructose.

2. Disaccharides: The carbohydrates, those that yield ONLY Two Monosaccharides on

hydrolysis are Disaccharides.
Example: Sucrose yields Glucose and Fructose. Maltose yields Two Glucose molecules.
 3. Trisaccharide’s: The carbohydrates, those that yield EXACTLY Three
Monosaccharides on hydrolysis are Trisaccharide’s.

Carbohydrates that yield 2 – 10 Monosaccharides on Hydrolysis are Oligosaccharides.

4. Polysaccharides: The carbohydrates, those that yield large number of

Monosaccharides (>10) on hydrolysis are Polysaccharides.
Example: Starch, Cellulose, Glycogen, Gums.
BASED ON REDUCING NATURE
1. Reducing Sugars: The carbohydrates those which REDUCE Fehling’s Solution and
Tollens Solution are Reducing Sugars.

Example: All Monosaccharides (Aldose or Ketose) are Reducing Sugars.

In Disaccharides, Maltose and Lactose are Reducing Sugars.

2. Non – Reducing Sugars: The carbohydrates those which DO NOT REDUCE

Fehling’s Solution and Tollens Solution are NON – Reducing Sugars.

Example: In Disaccharides, Sucrose is Non – Reducing Sugar.

In any Carbohydrate, if the Aldehydic or Ketonic group is NOT Bonded, then it would be a
Reducing Sugar.
In any Carbohydrate, if the Aldehydic or Ketonic group is Bonded, then it would be a
Non – Reducing Sugar.
MONOSACCHARIDES
Monosaccharides are further classified as (1) Aldose if contains an Aldehyde Group and
Ketose if contains a Ketone Group and (2) depending on number of Carbons present in the
Carbohydrate molecule.
Number of Carbons General Prefix Aldose Name Ketose Name
3 Triose Aldotriose Ketotriose
4 Tetrose Aldotetrose Ketotetrose
5 Pentose Aldopentose Ketopentose
6 Hexose Aldohexose Ketohexose
7 Heptose Aldoheptose Ketoheptose
Glucose
Glucose is a naturally occurring Monosaccharide and is an Aldohexose found in fruits, honey,
plants etc. It is prepared from Sucrose and Starch as:
Sucrose on reacting with water in presence of dil. HCl or H2SO4 produces Glucose and
Fructose in equal amounts.
𝐻+
𝐶12 𝐻22 𝑂11 + 𝐻2 𝑂 → 𝐶6 𝐻12 𝑂6 + 𝐶6 𝐻12 𝑂6
Starch on undergoing hydrolysis in presence of small amount of dil.H2SO4 at 393K under
pressure produces Only Glucose.
𝐻 + ,393𝐾,2−3𝑎𝑡𝑚
(𝐶6 𝐻10 𝑂5 )𝑛 + 𝑛𝐻2 𝑂 → 𝑛𝐶6 𝐻12 𝑂6
Glucose is the most common carbohydrate and a basic constituent. The structure of glucose is
very important as many enzymes and higher saccharides are derivatives of this primary basic
ingredient.
Linear Structure of Glucose: The structure was determined based on following few tests:
1. The molecular formulae is found to be C6H12O6.

2. Glucose on reacting with Hydrogen Iodide produced n – Hexane which implies that all
the 6 Carbon atoms are attached to each other forming a Linear Chain.

3. Glucose exhibited Addition Reactions with Hydrogen Cyanide and Hydroxylamine.

Such reactions are actually shown by Carbonyl Compounds which confirms the
presence of Carbonyl Group as Aldehyde or Ketone in Glucose.

4. Glucose formed Gluconic Acid on reacting with Bromine Water which confirms the
presence of Carbonyl Group in form of an Aldehyde.
 5. Glucose on reacting with Acetic Anhydride produced a Penta – Acetate compound
confirming the presence of Five Hydroxyl groups.

As, the compound is a stable one, it implies that all the five hydroxyl groups are present
on different carbon atoms.

6. Both Glucose and Gluconic Acid on reacting with Nitric acid produced Saccharic Acid
(consists two Carboxyl groups) indicating the presence of an Aldehyde and Primary
Alcohol Group.

Therefore, the exact structure of Glucose was given by Fischer after studying many properties
as:

To differentiate between different forms of Carbohydrates, we use the following two notations:
1. Based on Optical Activity: d – and l – or (+) and (-) notations are used.

2. Based on configuration with respect to Glyceraldehyde: D and L are used as:

Any carbohydrate having a configuration at the Last Asymmetric Carbon similar to D –
Glyceraldehyde and L – Glyceraldehyde are given D and L configurations respectively.

Cyclic Structure of Glucose: The Linear structure of Glucose explained most of its properties
but a few reactions aren’t showed by Glucose such as:
1. No reaction with 2, 4 DNP, Schiff’s Test and No Addition Reaction with Sodium
Hydrogen sulphate.

2. The Penta Acetate form of Glucose didn’t show any Addition Reaction with
Hydroxylamine indicating the Absence of Free Aldehyde.

3. Glucose existed in two different crystalline forms:

✓ α – Glucose existed at 303K. Obtained from crystallization of hot conc. sol. of

Glucose.

✓ β – Glucose existed at 371K. Obtained by crystallization of hot saturated sol. of

Glucose.
In order to explain the above observations, the linear form of Glucose is modified and
proposed to have a Cyclic Structure with one of the Hydroxyl groups reacting with
Aldehyde group forming a Cyclic Hemi – Acetal Structure.
Experimentally, it was determined that – OH on 5th Carbon reacts with the Aldehyde carbon
and forms the cyclic structure.
The two cyclic crystalline forms exist in equilibrium with each other as well as with the
open chain form.
The two Cyclic Hemiacetal forms differ in Configuration ONLY at the 1st Carbon called as
Anomeric Carbon (before Cyclic Structure is formed). Hence, α and β forms of Glucose are
called as “Anomers”.
The Cyclic Form of Glucose is also called Pyranose Structure
(Analogous to Pyran – 6 membered Cyclic Structure with one of the Atoms as Oxygen)
The Cyclic structure of Glucose is exactly represented by Haworth Structures as:

Fructose
Fructose is a naturally occurring Monosaccharide and is a Ketohexose. It is obtained along
with Glucose.
✓ Fructose also has a molecular formulae C6H12O6 and contains a Ketonic group on 2nd
Carbon with all the six carbons in straight chain similar to Glucose.

✓ Fructose exists in D form and Laevorotatory in nature.

✓ Fructose also exists in Cyclic form as:

 ✓ The two Cyclic Hemiacetal forms differ in Configuration ONLY at the 2nd Carbon called
as Anomeric Carbon (before Cyclic Structure is formed). Hence, α and β forms of
Fructose are called as “Anomers”.
The Cyclic Form of Fructose is also called Furanose Structure
(Analogous to Furan – 5 membered Cyclic Structure with one of the Atoms as Oxygen)
The Cyclic structure of Fructose is exactly represented by Haworth Structures as:

DISACCHARIDES
Disaccharides are the “Carbohydrates formed when Two Monosaccharides are joined to each
other through Oxygen atom and such a linkage is called as Glycosidic Linkage”.
The Monosaccharides are joined to each other using Oxygen present on different Carbons
present in the Monosaccharides.
A few disaccharides in detail:
Sucrose
The most common disaccharide formed by equimolar mixture of D (+) Glucose and D (-)
Fructose through Glycosidic Linkage.
𝐻+
𝐶12 𝐻22 𝑂11 + 𝐻2 𝑂 → 𝐶6 𝐻12 𝑂6 + 𝐶6 𝐻12 𝑂6
✓ The two monosaccharides are joined through C1 of α – Glucose and C2 of β – Fructose.

✓ As the Reducing groups in both the compounds are bonded and NOT in free state,
Sucrose is a Non – Reducing Sugar.

✓ Sucrose is Dextrorotatory but after hydrolysis, Glucose and Fructose are produced
with Optical Rotation of +52.5 and –92.4 respectively. Hence, the mixture produced
will be Laevorotatory and this is called Invert Sugar.
Maltose
Maltose is a disaccharide formed by the Glycosidic Linkage between C1 of One D (+) Glucose
with C4 of another D (+) Glucose.
✓ The C1 of the second glucose molecule is free and NOT Bonded to anything, hence
Maltose is a Reducing Sugar.

Lactose
Lactose is found in Milk and hence, also known as Milk Sugar. It is a disaccharide formed by
the Glycosidic Linkage between C1 of β – D Galactose with C4 of β – D Glucose.
✓ The C1 of the Glucose molecule is free and NOT Bonded to anything, hence Lactose is
a Reducing Sugar.
POLYSACCHARIDES
Polysaccharides form major sources of Carbohydrates either as Food Storage or Structural
Materials. These contain a large number of Monosaccharides joined to each other through
Glycosidic Linkages.
A few Polysaccharides in detail:
Starch
The most common polysaccharide found in Plants. It is the most important dietary source for
human beings.
✓ It is a Polymer of Amylose and Amylopectin.

✓ Amylose is a water – soluble component constituting 15 – 20% of the total Starch.

✓ Amylose is long chain polymer with 200 – 1000 units of α – D Glucose held to each
other by C1 – C4 Glycosidic Linkages.

✓ Amylose is Water Insoluble component constituting 80 – 85% of total Starch and is a

Branched polymer of α – D Glucose with C1 – C4 Glycosidic Linkages in Linear Chain
and C1 – C6 Glycosidic Linkage in the Branching.
Cellulose
The most abundant organic substance that is exclusively found in Plants. It is a predominant
constituent of cell wall of plant cells.
✓ It is a Straight Chain Polymer composed of ONLY β – D Glucose.

✓ Formed by Glycosidic Linkage between 1st Carbon of One Glucose with 4th Carbon of
2nd Glucose i.e. C1 – C4 Linkage.

Glycogen
It is the form of Carbohydrate stored in Animals. Hence, also known as Animal Starch as the
structure is similar to Amylopectin and also highly branched in nature.
✓ Present in Liver, Muscles and Brain.

✓ On requirement of Energy, body breaks Glycogen into Glucose using Enzymes and
utilize the Glucose.

✓ Also found in Yeast and Fungi.

APPLICATIONS
✓ As storage molecules in plants and animals.

✓ Cell wall of bacteria and plants is made up of cellulose.

✓ Cellulose fibres are used in Textiles.

✓ Few Sugars are exclusively present in Nucleic Acids which carry Hereditary
Information over Generations.
 PROTEINS

Proteins are “Polymers made up of α – Amino Acids joined to one another through Peptide
bonds”. “Proteins are Polyamides consisting of more than 20 different amino acids in one
monomeric unit”.
Proteins perform various functions such as:
✓ Enzymes and Hormones, Catalysing many Chemical Reactions

✓ Muscles and Tendons, helps in Movement of Muscles

✓ Skin and Hair, providing Covering and giving Protection

✓ Antibodies helping Immune System in Fighting against Diseases

✓ Providing Structural support to the body.

Proteins exist in Various Shapes and Sizes with complex Globular Structures to simple Helical
structure having molecular mass greater than 12,000amu even for small sized Proteins. For
example, Lysozyme a small protein has molecular mass of 14,600g/mol.
✓ Proteins are compounds composed of ONLY α – Amino Acids.

✓ Hydrolysis of Naturally occurring proteins, produces 22 α – Amino acids.

AMINO ACIDS
Amino acids are the compounds containing minimum One each of Amino group and Carboxyl
group. Depending on the position of the two groups relative to each other, compounds are
designated as α, β, γ, δ – Amino Acids etc.

L – Amino Acid D – Amino Acid

The “R” group present in the Amino Acid can be any other element or molecule.
In an Amino Acid, if the –NH2 is present on Left side of –COOH, it is considered as “L – Amino
Acid” and if present on right side, as “D – Amino Acid”.
Most of the naturally occurring Amino Acids are L – configured.
If “R” is any molecule other than –H, –NH2, –COOH, Amino Acid becomes “Optically Active
as the Carbon becomes Asymmetric”.
PROPERTIES OF AMINO ACIDS
✓ Are Colourless

✓ Highly soluble in water due to formation of Dipolar ion as well as due to High
Intermolecular Hydrogen Bonding.

✓ Have High Melting points as they behave like Ionic Salts rather than Covalent
compounds due to presence of both Acidic as well as Basic Groups.

✓ Amino Acids exist as Zwitter ions in Dry Solid State. i.e. Carboxyl group loses H+ ion
whereas Amino group accepts H+ ion making the molecule Dipolar but Electrically
Neutral in Nature.

✓ Amino Acids when dissolved in aqueous media forms Zwitter ions which exists in
equilibrium with both the Cationic and Anionic forms of Amino Acid.

✓ Zwitter ion is Amphoteric and hence, can react with both Acids as well as Bases.

✓ In Strongly Acidic medium, Cationic form exists predominantly.

✓ In Strongly Basic medium, Anionic form exists predominantly.

✓ Isoelectric Point is “the pH at which the concentration of Dipolar ion is Maximum and
the concentration of both Anionic and Cationic forms are equal”.

✓ At Isoelectric Point, there would be complete Electrical Neutrality in the solution.

✓ Isoelectric Point in Amino acids containing only Hydrocarbons in attached group, is

calculated as:
𝑝𝐼 = 𝑝𝐾𝑎1 + 𝑝𝐾𝑎2
where, pKa1 & pKa2 are the pH values at which H+ ion is lost from Carboxyl & Amino groups respectively.
FORMATION OF PROTEINS
✓ Individual Protein strands (Primary Proteins) are formed when the Amino Acids are
joined to each other using Carbon – Nitrogen bond.

✓ Protein strands on overlapping with one another forms complex and higher proteins.
The number of protein strands overlapping in the process gives the complexity.

✓ In living entities, Proteins are formed in presence of “Enzymes” that acts as Catalysts.

✓ In the bond formation, Hydrogen from Amino group and OH from Carboxyl group
reacts with each other resulting in an Amide formation whereas the two ions are lost
as a Water Molecule.

✓ The Amino Acids reacting can be same or different. The number of Amino acids
involved in and the way the bond formation is occurring determines the complexity.

✓ Hence, Proteins are also considered as Polyamides and the Amide bond is also called
as Peptide Bond or Peptide Linkage. Therefore, Proteins are even considered as
Polypeptides.

✓ Example:
• If 3 different Amino Acids combine with each other, 6 different sequences are possible.
• If 4 different Amino Acids combine with each other, 24 different sequences are possible.

Depending on the number of Amino Acids linked to each other, the product is called
accordingly as:
Dipeptide for Two Amino Acids Pentapeptide for Five Amino Acids
Tripeptide for Three Amino Acids Hexapeptide for Six Amino Acids
Tetrapeptide for Four Amino Acids Polypeptide for ≥ Ten Amino Acids

GENERAL INFORMATION:
If 20 Amino Acids react with each other and form a Single Residue chain, then 2100 different
sequences of Proteins are possible by different way of combining with each other.
2100 = 1.27 × 10130 number of combinations are possible whereas the total number estimated
atoms in universe is ONLY 9 × 1078 atoms.
CLASSIFICATION OF PROTEINS
1. Fibrous Proteins: The polypeptide strands (chains) when run parallel to each other
and are held close to each other through Hydrogen or Sulphide bonds forms Fibre like
structures. The fibres are known as Fibrous Proteins. Fibrous Proteins are Insoluble
in Water.
Example: Keratin and Myosin.

2. Globular Proteins: The polypeptide chains when runs around each other forming a
spiral or helical structure results in proteins known as Globular Proteins. Globular
Proteins are Soluble in Water.
Example: Egg Albumin and Insulin
Proteins are made up of many polypeptide chains/ strands. Each chain/ strand contains different
amino acids and different in number also.
3. Primary Structural Proteins: The individual polypeptide chain is considered as
Primary Protein. It is generally short in length.

Every Primary Protein contains a definite sequence of Amino Acids and even if the
sequence is altered with same amino acids, the new peptide chain resulting in will be
completely different having different functions altogether.

4. Secondary Structural Protein: The long polypeptide chains forms Intramolecular and
Intermolecular Hydrogen bonds between the Carbonyl Group and Amino Group.

Due to this bonding two different structures are formed as:

α – Helical Structure: The strand looks like a Helix (Right Hand Screw) having
extensive Intramolecular Hydrogen Bonding between the molecules on the adjacent
turns to each other in the helix.

β – Plated Sheet Structure: The strands are completely stretched out to maximum extent
and then laid side by side forming Intermolecular Hydrogen Bonding between the
stretched strands.

5. Tertiary Structural Proteins: The secondary structural proteins on folding with each
other forms Tertiary Structural Proteins.

Hydrogen Bonding, Disulphide Linkages, Vander wall’s and Electrostatic Forces of

Attraction stabilizes these complex proteins.

6. Quaternary Structural Proteins: The polypeptide strands that are completely inter –
tangled with each other in a complex way forms Quaternary Structural Proteins.

An Extensive Intermolecular as well as Intramolecular Hydrogen Bonding, Disulphide

Linkages, Vander wall’s and Electrostatic Forces of Attraction etc. stabilizes these
proteins.
PROPERTIES OF PROTEINS
✓ Proteins found in a biological system with a specific activity are considered as “Native
Proteins”.

✓ The structure of Native proteins changes when subjected to change in pH, temperature
etc. due to disturbance or breaking in the Hydrogen Bonds, Disulphide bonds.

✓ As a result, higher proteins (Globular Proteins) start unfolding, forming Primary

proteins resulting in the loss of the Biological Activity of Proteins. The process is called
“Denaturation of Proteins”.

✓ Boiling of Egg, Curdling of Milk are examples of Denaturation of Proteins.

 Structure of Quaternary Proteins 

 ENZYMES

In all the biological systems, “Reactions occur continuously and most of the reactions are
catalysed by a few chemicals, required in very small quantity” which are known as Biological
Catalysts or Enzymes.
✓ The reactions of cellular metabolism are mediated by remarkable biological catalysts
called Enzymes.

✓ The Rate of Catalysed Reactions are 106 – 1012 times greater than those of Uncatalyzed
Reactions.

✓ Enzymes show remarkable specificity for their substrates and forms highly specific
products.

✓ In general, Enzymes follow Lock and Key Mechanism (seen in Surface Chemistry).
Enzyme + Substrate ↔ Enzyme – Substrate Complex ↔ Enzyme + Product
✓ Reactions catalysed by Enzymes are Stereospecific as Enzymes are Optically Active
Chemical substances.

✓ Oxidoreductase Enzymes are the “Enzymes which Oxidize One Substrate and Reduce
other Substrate simultaneously”.

✓ The Activation Energy for Acidic Hydrolysis of Sucrose is 6.22kJ mol-1 whereas the
Activation Energy for Sucrase Catalysed Hydrolysis of Sucrose is 2.5kJ mol-1.

✓ A compound that negatively effects the Enzyme or reduces the Functionality of Enzyme
is known as “Inhibitor”.

VITAMINS

In all the biological systems, “The reactions that take place requires certain Organic
substances in very small quantities whose deficiency leads to diseases”. Such substances are
considered as Vitamins.
Vitamins can also be defined as, “The organic compounds that are required in small amounts
to perform specific biological functions for normal maintenance of optimum growth and health
of the organism which are to be provided though daily diet”.
✓ Most of the Vitamins cannot be produced by Humans but Plants can produce all of them
and hence, are considered as “Essential Food Factors”.
 ✓ The classification of Vitamins Based on Structure is highly difficult and therefore are
classified Based on Solubility factor.

✓ Excess of Vitamins are Extremely harmful to the humans. Therefore, are not be
consumed without Doctors Consultation.

✓ The word “Vitamine” was used initially assuming it is “Vital + Amine” but later
changed to Vitamin understanding that Vitamins DO NOT CONTAIN AMINO
ACIDS.
CLASSIFICATION OF VITAMINS
1. Fat Soluble Vitamins: Vitamins which are Soluble ONLY in Fats and Oils but Insoluble
in Water are considered as such. Such Vitamins are stored in Liver and Adipose tissues.
Example: Vitamin A, D, E and K respectively.
2. Water Soluble Vitamins: Vitamins which are Soluble ONLY in Water but Insoluble in
Fats and Oil are considered as such. Such Vitamins are to be supplied through Diet on
regular basis as they get lost from the system during Excretion Process.
Example: Vitamins B (except B12) and Vitamin C.
As the deficiency of Vitamins causes diseases, the following table gives the list of Vitamins
whose deficiency causes diseases and foods to be consumed to prevent such diseases as:
Vitamin Disease Caused Disease Preventive Foods
Night Blindness Fish Liver Oil, Carrots,
A
Xerophthalmia Butter and Milk
Yeast Milk, Green
B1 Beri Beri (Loss of Weight)
Vegetables and Cereals
Digestive Disorders
Cheilosis (Fissuring at Milk, Egg White, Liver,
B2
Corners of Lips) Kidney
Burning Sensation on Skin
Yeast, Milk, Egg Yolk,
B6 Convulsions
Cereals
B12 Pernicious Anaemia Meat, Fish, Egg and Curd
Citrus Fruits, Amla and
C Scurvy (Bleeding Gums)
Green Leaf Vegetables
Rickets (Bone Deformations) Exposure to Sunlight, Fish
D
Osteomalacia (Joint Pains) and Egg Yolk
Increased Fragility in RBC
E Vegetables Oils
(Muscle Weakness)
K Delayed Clotting of Blood Green Leaf Vegetables
 NUCLEIC ACIDS

The transfer of Information, Functions, Identicalities etc. from Parents to their off springs
occur due to the presence of Nucleic Acids known as RNA and DNA.
✓ RNA and DNA are the Genetic Information Carrying and Transferring Molecules in
the cells.

✓ DNA is the archive of instructions for the Protein Synthesis.

✓ RNA molecules transcribe and translates the information for protein synthesis.

✓ The storage of information, its passage from generation to generation and use of
genetic information to create proteins depends on the Molecular Structure of both DNA
as well as RNA.

✓ Each section of DNA that codes for a Protein is called as “Gene”.

✓ The set of all Genetic Information coded by DNA in an organism is called “Genome”.

✓ In a Human Genome, there are 30,000 – 35,000 Genes approximately.

We shall study ONLY about Nucleotides and Nucleosides present in DNA and RNA.
CHEMICAL COMPOSITION OF NUCLEIC ACIDS
RNA and DNA are made up of Nucleotides and Nucleosides which in turn are made up of:
Pentose Sugar, Phosphoric Acid and Heterocyclic Base containing Nitrogen

1. RNA: Nucleotides in RNA molecules consists of:

✓ Sugar base known as β – D Ribose

✓ Nitrogenous Bases such as Adenine, Guanine, Cytosine and Uracil

✓ Phosphate ion

2. DNA: Nucleotides in DNA molecules consists of:

✓ Sugar base known as β – D – 2 Deoxyribose

✓ Nitrogenous Bases such as Adenine, Guanine, Cytosine and Thymine

✓ Phosphate ion
CHEMICAL STRUCTURE OF NUCLEIC ACIDS
RNA and DNA are made up of 3 substituents attached to each other in a highly Specific manner.
Primary Structure of RNA and DNA:
✓ The Carbons in the Sugar are number as 1’, 2’, 3’, 4’, 5’ respectively.

✓ The Carbon at 1’ position in the Sugar reacts with the Nitrogenous Base forming
“Nucleoside”.

✓ The Hydroxyl Group present on 5’ Carbon in Nucleoside reacts with the Phosphoric
Acid forming “Nucleotide”.

✓ The Phosphoric acid joins two or more Nucleosides through 3’ and 5’ Carbons forming
Higher Nucleotides.

✓ The Nucleotides when joined forming a Linear Structure gives rise to Primary Nucleic
Acid.
Secondary Structure of DNA:
✓ Two primary chains wound about each other using Hydrogen Bonds give rise to
Secondary Nucleic Acids having Helical Structure.

✓ The two strands are Complimentary to each other as the Hydrogen Bonds are formed
only between specific bases.
Secondary Structure of RNA:
✓ The Single strands fold back onto themselves forming a Double Stranded Helix
Structure.
RNA is of three different types and all three performs different functions as:
✓ m – RNA: Messenger RNA

✓ r – RNA: Ribosomal RNA

✓ t – RNA: Transfer RNA

BIOLOGICAL FUNCTIONS OF NUCLEIC ACIDS
✓ Can Self – Duplicate itself and transfer the duplicate cells to the Daughter Cells

✓ Synthesize Proteins in the Cells.

✓ RNA synthesises the Protein Cells but the order for Synthesizing a particular type of
Protein is present in DNA.

✓ Hence, IFF DNA directs, RNA will synthesize Proteins and Nucleic Acids.
 Structures of Sugar Present in RNA (β – D Ribose) and DNA (β – D – 2 Deoxyribose)

Segment of DNA Strand with Four Different Bases Joined at 3’ and 5’ Position of Sugar