Biomolecules – chemicals or molecules present in the living organisms

 Biomolecules is a compound of carbon (carbon is the most versatile and the most predominant of
life).
Cellular pool – the sum total of different types of biomolecules, compounds, and ions present in a cell

BIOMOLECULES
Inorganic Organic Micro molecules
Minerals, Gases,
Minerals Carbohydrates  Small sized , low mol wt Water, Sugars,
Gases Lipids  Between 18 and 800 daltons Amino Acids,
 Found in the acid soluble Nucleotides
Water Amino Acid pool
Proteins Macro molecules
Enzymes Carbohydrates,
 large sized , high mol wt
 Above 10000 daltons Lipids, Proteins,
Nucleotides Nucleic Acid
 Found in the acid insoluble
Nucleic Acid pool

Vitamins

THE MAJOR COMPLEX BIOMOLECULES OF CELL

Biomolecule Building block Major functions

Protein Amino acid Basic structure and function of
cell
DNA Deoxyribonucleotide Hereditary information
RNA Ribonucleotide Protein synthesis
Polysaccharide Monosaccharide Storage form of energy
Lipid Fatty acids & glycerol Storage form of energy to meet
long term demands

CARBOHYDATES
 are the most abundant organic molecules in nature.
 The term “carbohydrate” is derived from the French term “hydrate de carbone,” which means it is
a hydrate of carbon or Cn(H2O)n. 
 Carbohydrates are defined as organic substances having C, H & O, wherein H and O are in the
ratio 2:1 as found in H2O.

Functions of Carbohydrates
Energy Source: Carbohydrates are the Precursors for Organic
most abundant source of energy, Compounds: They serve as
providing approximately 4 calories per precursors for the synthesis of Energy Storage:
gram. other organic compounds, Glycogen, a type of
including fats and amino acids. carbohydrate,
serves as a storage
form of energy to
Cell Membrane Components: meet the body’s
Carbohydrates are present as Structural Components: Some demands.
glycoproteins and glycolipids in the carbohydrates, like cellulose in
cell membrane, contributing to plants, form structural components
functions such as cell growth and such as cell walls and the
fertilization. exoskeleton of certain insects.

CARBOHYDATES
Monosaccharides Oligosaccharide
Polysaccharide
 Basic unit of  They can be further
carbohydrates, hydrolyzed  Non crystalline, non-
cannot be hydrolyzed o Disaccharide soluble in water,
into smaller unit o Trisaccharide tasteless, on
o Based on the no. o Tetrasaccharide hydrolysis gives mol
of C- atoms of monosaccharides.
o Based on the Eg. Starch and
type of cellulose
functional group

DERIVATIVES OF MONOSACCHARIDES

Deoxy Sugars: Amino Sugars: When one or Sugar Acid: Oxidation of –CHO
Deoxygenation of ribose more –OH groups of or –OH groups forms sugar
produces deoxyribose, monosaccharides are replaced acids. Ascorbic acid (vitamin C) is
which is a structural by –NH₂ (amino group), it an example of a sugar acid.
component of DNA. forms an amino sugar. For
example, Glucosamine forms
chitin, fungal cellulose, and Sugar Alcohols: Reduction of
hyaluronic acid. aldoses or ketoses leads to sugar
alcohols. Examples
include glycerol and mannitol.
 OLIGOSACCHARIDE

Depending on the number of

Disaccharides: Trisaccharides: Comprising
monosaccharide molecules they
.  These
contain, they are categorized as consist of two three monosaccharide
Oligosaccharides follows: monosaccharide units. units, raffinose is an example.
are formed by the  Examples:
condensation of 2 sucrose (table sugar)
to 9 and lactose (found in
Tetrasaccharides: These
monosaccharides milk).
contain four monosaccharide
 smallest and most
units. An example
common
is stachyose.
oligosaccharides

Disaccharide
A disaccharide
consists of two monosaccharide units (similar or dissimilar) held together by a glycosidic bond.

These compounds exhibit the following characteristics:

Maltose: Lactose: Sucrose:

 Also known as malt  Referred to as milk  Also called cane
sugar. sugar because it is sugar.
 Composed of two naturally found in  Most abundant among
glucose molecules. milk. naturally occurring
 Crystalline, water-  Composed of glucose sugars.
soluble, and sweet to and galactose.  An important source
taste.  The souring of milk is of dietary
due to the conversion carbohydrates.
of lactose to lactic  Composed of glucose
acid. and fructose.

POLYSACCHARIDE

Polysaccharides, also known as glycans, are composed of repeating units of monosaccharides held
together by glycosidic bonds. Key characteristics of polysaccharides include:
Formation and Water Release:
 During their formation, a water molecule is released in each condensation step.
 This reduction in bulk makes them almost insoluble, minimizing their impact on
the water potential or osmotic potential of the cell.
Sweetness and Solubility:
 Unlike sugars, polysaccharides are not sweet.
 They are ideal for both storage and as structural components.
 Types of Polysaccharide

Homoglycans: Heteroglycans:
 Composed of only one type of  Formed by the
monosaccharide monomers. condensation of two or
 Examples: Starch, glycogen, more types of
cellulose. monosaccharides.
 Subtypes: Glucan (made up of  Examples: Hyaluronic
glucose), Fructan (made up of acid, agar, chitin,
fructose), Galactan (made up of peptidoglycans.
galactose).

Storage of Polysaccharide

Starch Glycogen

 Carbohydrate reserve  Carbohydrate reserve in animals (referred to

of plants and the most as animal starch).
important dietary  High concentration in the liver, muscles, and
source for animals. brain.
 High content of starch  Also found in non-chlorophyll-containing
in cereals, roots, plants (such as yeast and fungi).
tubers, and vegetables.  The repeating unit is glucose.
 A homopolymer made
up of glucose Inulin
units (also
called glucan).  A polymer of fructose (referred to
 Starch consists of two as fructosan).
components: Amylose  Found in plants like Dahlia, bulbs, garlic,
and Amylopectin. and onion.
 Easily soluble in water.
 Not readily metabolized in the human body,
making it useful for testing kidney function
(glomerular filtration rate - GFR).

Structural of Polysaccharide
 Cellulose: Chitin:
 Occurs exclusively in plants and  The second most abundant
is the most abundant organic organic substance.
substance in the plant kingdom.  A complex carbohydrate of the
 Predominant constituent of the heteropolysaccharide type.
plant cell wall.  Found in the exoskeletons of
 Absent in animals. some invertebrates, such as
insects and crustaceans. It
provides both strength and
elasticity.
 Becomes hard when impregnated
with calcium carbonate

AMINO ACID
 Amino acids are a group of organic compounds having two functional groups: -
NH₂ (amino group) and -COOH (carboxyl group).
 The -NH₂ group is basic, whereas the -COOH group is acidic.
 The R group can be:
 H in glycine,
 CH₃ in alanine,
 Hydroxymethyl in serine,
 In others, it can be a hydrocarbon chain or a cyclic group.
 All amino acids contain C, H, O, and N, but some of them additionally contain S.
 The physical and chemical properties of amino acids are due to the amino, carboxyl,
and R functional groups.

Groups of Amino Acid

No. Nature Amino Acid

1 Neutral Amino Acids (1 amino and 1  Glycine (Gly)
carboxyl group)  Alanine (Ala)
 Valine (Val)
 Leucine (Leu)
 Isoleucine (Ile)

2 Acidic Amino Acids (1 extra carboxyl  Aspartic acid (Asp)

group)  Asparagine (Asn)
 Glutamic acid (Glu)
 Glutamine (Gln)

3 Basic Amino Acids (1 extra amino group)  Arginine (Arg)

 Lysine (Lys)

4 Sulfur-Containing Amino Acids  Cysteine (Cys)

  Methionine (Met)

5 Alcoholic Amino Acids (having -OH  Serine (Ser)

group)  Threonine (Thr)
 Tyrosine (Tyr)

6 Aromatic Amino Acids (having cyclic  Phenylalanine (Phe)

structure)  Tryptophan (Trp)

7 Heterocyclic Amino Acids (having N in  Histidine (His)

ring structure)  Proline (Pro)

Peptide Formation
 Amino acids are linked serially by peptide bonds (-CONH-) formed between the (-NH₂)
of one amino acid and the (-COOH) of the adjacent amino acid.
 A chain having two amino acids linked by a peptide bond is called a dipeptide.
 The sequence of amino acids present in a polypeptide is specific for a particular protein.

PROTEINS
 Most abundant organic molecules in living systems.
 Form about 50% of the dry weight of the cell.
 Crucial for the architecture and functioning of the cell.
Proteins are polymers of amino acids:
 Complete hydrolysis of proteins yields amino acids.
 There are 20 standard amino acids that are repeatedly found in the structure of proteins
(animal, plant, or microbial).
 Collagen is the most abundant animal protein, and Rubisco is the most abundant plant
protein.
 Protein synthesis is controlled by DNA.

Protein Structure

Primary Structure:
 Refers to the number and linear sequence of amino acids in the polypeptide chain.
 Determines the function of the protein.
 The N-terminal amino acid is written on the left side, while the C-terminal amino acid is
written on the right side.
 Protein Functional Classification

Structural Proteins: Enzymatic Proteins: Transport Proteins:

 Examples:  Example: Pepsin  Example:
Keratin, Collagen  Function: Act as Hemoglobin
 Function: Provide biological catalysts,  Function: Carry
support and shape speeding up molecules (e.g.,
to tissues and chemical reactions. oxygen) within the
organs. body.

Hormonal Proteins: Contractile Proteins: Storage Proteins:

 Examples:  Examples: Actin,  Example: Ovalbumin
Insulin, Growth Myosin  Function: Store
hormone  Function: Enable amino acids for
 Function: muscle contraction future use.
Regulate and movement.
physiological
processes and
communication
between cells.
Defence Proteins: Receptor Proteins:
 Example:  Example: Receptors
Genetic Proteins: Immunoglobulins for hormones and
 Example: (antibodies) viruses
Nucleoproteins  Function: Protect  Function: Receive
 Function: Play a against pathogens signals and transmit
role in DNA and foreign them into the cell.
replication and substances.
gene expression.

Classification of Proteins Based on Chemical Nature and Solubility

Simple Proteins: Conjugated Proteins: Derived Proteins:

 Composed only of  Along with amino acids, there  Denatured or
amino acid is a non-protein prosthetic degraded products
residues. group. of the above two
 Examples:  Examples: Hemoglobin  Examples: Peptides,
Albumins, (contains heme), Lipoproteins Polypeptides.
Globulins.
(contain lipids), Glycoproteins  With Primary and
 Is Globular and
(contain carbohydrates). Secondary
Fibrous
 LIPIDS
Lipids are the chief concentrated storage form of energy forming about 3.5% of the cell content.
Lipids are organic substances relatively insoluble in water but soluble in organic solvents (alcohol, ether).
Functions:
1. They are the concentrated fuel reserve of the body.
2. Lipids are constituents of membrane structure and regulate the membrane permeability.
3. They serve as a source of fat-soluble vitamins.
4. Lipids are important cellular metabolic regulators.
5. Lipids protect the internal organs and serve as insulating materials."

Simple Lipids

Simple lipids are esters of fatty acids with alcohol. They can be categorized into two main types:
1. Neutral or True Fats: These are esters of fatty acids with glycerol.
2. Waxes: These are esters of fatty acids with alcohol other than glycerol.

Neutral/True Fats: Waxes

 True fats are composed Glycerol: A Waxes are lipids composed of long-chain
of carbon ©, hydrogen glycerol molecule saturated fatty acids and a long-chain saturated
(H), and oxygen (O), has 3 carbons, each alcohol of high molecular weight other than
but oxygen is present in bearing an –OH glycerol. Let’s explore some examples of
smaller quantities. group. waxes:
 A fat molecule consists 1. Beeswax: This is the secretion of
of two main abdominal glands in worker honey
components: bees.
 Glycerol: The Fatty acid: A fatty 2. Lanolin (Wool Fat): Obtained from
backbone of acid molecule is an the wool of sheep, lanolin is a
the fat unbranched chain of secretion of cutaneous glands.
molecule. carbon atoms. It has 3. Sebum: Sebum is the secretion of
 Fatty Acids: a –COOH group at sebaceous glands in the skin.
One to three one end and a 4. Cerumen (Earwax): A soft and
molecules of hydrogen atom brownish waxy secretion produced by
fatty acids, bonded to almost all glands in the external auditory canal.
which can be of the carbon atoms. 5. Plant Wax: Coating formed on plant
the same or Fatty acids may be organs to prevent transpiration.
different chain saturated or 6. Paraffin Wax: A translucent waxy
lengths. unsaturated. substance obtained from petroleum.

Complex Lipids

Complex lipids are derivatives of simple lipids and contain additional groups such as phosphate,
nitrogen bases, or proteins. They can be further categorized into three main types:

Phospholipids:
 Derived Lipids

Derived lipids are obtained from the hydrolysis of simple and complex lipids. They
include compounds like steroids, terpenes, and prostaglandins.

Steroids:
 Steroids are a class of derived lipids.
 Unlike other lipids, steroids do not contain fatty acids.
 ENZYMES
 Enzymes are a group of catalysts that function in biological systems.
 They are usually proteinaceous substances produced by living cells.
 Enzymes enhance the rate of chemical reactions without being consumed themselves.
 These catalysts are formed within cells based on instructions from genes.
 Enzymes exist in a colloidal state.
 They are often produced in an inactive form called proenzymes (or zymogens).
 Specific factors like pH and substrate convert proenzymes into their active forms.
 Enzymes can be categorized as:
o Endoenzymes: Produced within a cell for metabolic activities.
o Exo-enzymes: Act away from the site of synthesis.
Enzymology:
o Enzymology is the branch of science that deals with the study of enzymes.
o It encompasses aspects such as nomenclature, reactions, and functions of enzymes

General Properties of Enzymes and Factors Affecting Their Activity

Enzymes Accelerate
Reactions: Enzymes
facilitate chemical
reactions by speeding
up the rate of reaction.
 Enzymes Remain Active Site: Enzymes have a Amphoteric Nature: Most
Unchanged: Enzymes specific part called the enzymes are proteins and
do not actively “active site.” During a exhibit amphoteric behavior.
participate in the reaction, this active site They can react with both
reaction; they remain interacts with the substrate acidic and alkaline
unchanged at the end of molecule. Enzymes are substances.
the process. Due to this larger than substrate
property, enzymes are molecules.
required in small
quantities.

Specificity: Most enzymes exhibit specificity in their action. Colloidal Nature: Enzymes are colloidal in
Each enzyme acts upon a single substrate or a closely related nature. This property provides them with a
group of substrates. large surface area for reactions to occur.
o For example: Colloids consist of dispersed particles and a
o Urease specifically acts on urea. dispersion medium. The size of the dispersed
particles (enzymes) is larger than that of the
o Invertase specifically acts on sucrose.
dispersion medium.
o Even a slight change in the substrate’s configuration
requires a different enzyme for action.

Enzyme Optima:
o Enzymes function optimally under specific conditions, often referred to as “optima.”
o These conditions include the appropriate temperature and pH.
a) Temperature Sensitivity:
o Enzymes are proteins, and their activity is affected by temperature changes.
o Up to around 40°C, enzyme activity increases with rising temperature.
o However, at temperatures above 60°C, proteins undergo denaturation or even complete
breakdown.
o Enzymes become inactivated when the temperature drops to freezing point or below,
but they are not destroyed.
o The rate of reaction is highest at the optimum temperature.
b) pH Sensitivity:
o Most enzymes exhibit specificity to a particular pH range.
o Strong acids or bases can denature enzymes.
o Intracellular enzymes typically function best around neutral pH.

Concentration of Enzyme and Substrate: Enzyme Inhibitors:

o The rate of reaction is directly o Enzyme inhibitors are specific
proportional to the concentration of the products that hinder enzyme
reacting molecules. activity.
o When substrate concentration increases, o During a reaction, if an inhibitor
enzyme activity also increases up to a occupies the enzyme’s active
certain limit. site instead of the substrate
o Beyond that concentration, enzyme molecule, enzyme activity is
molecules become saturated with lost.
substrate molecules, and the activity o Competitive inhibitors have a
levels off. similar structure to substrate
molecules.
 Group of enzymes Reaction catalyzed Examples
Oxidoreductases: These enzymes facilitate the Dehydrogenases and oxidases
transfer of oxygen or
hydrogen atoms or electrons
from one substrate to another.

Transferases: Transferases move specific Transaminases.

groups from one substrate to
another.

Hydrolases Hydrolases catalyze the Commonly found in digestive

hydrolysis of substrates. enzymes.

Isomerases Isomerases alter the Phosphohexoisomerase

molecular form of the
substrate

Lyases Lyases perform non- Decarboxylases and aldolases

hydrolytic removal or
addition of groups to
substrates

Ligases Ligases join two molecules Citric acid synthetase

by forming new chemical
bonds