Basic Biological Reactions
Presented by :
Meenakshi Das
M.Sc. 1st Semester
Department of Life Science and Bioinformatics
Assam University, Silchar

Introduction
Living Organisms and Chemical reactions
• Biological processes are the processes vital for
a living organism to live.
• Biological processes are made up of many
chemical reactions that give rise to chemical
transformation.
• Metabolism is the example.

Metabolism
• Metabolism is the sum total of
all the biochemical reactions.
• Functions of metabolism are:
1. Synthesis of biomolecules.
2. Transport of ions and
molecules across cell
membranes.
3. Production of force and
movement.
4. Removal of metabolic wastes
and other toxic substances.
Metabolism = Anabolism + Catabolism

Biochemical Reactions
• Chemical reactions associated with biological
processes are of following main types:
Neutralization Reaction
Condensation Reaction
Oxidation-Reduction Reaction
Group transfer Reaction
Hydrolysis Reaction
Reactions involved in formation or removal of a double bond
with group transfer
Isomerization Reaction
Reactions involved in single bond formation by eliminating
the elements of water

Biological Reactions and Enzymes
ENZYME is a Biological CATALYST
Enzyme speeds up a biological reaction by
lowering activation energy
Enzymes are not used up during a reaction and can
be used over and over again
Enzymes are proteinaceous in nature (except –
Ribozyme)
 Enzymatic reactions are reversible
Enzymes are specific that is they control only one
reaction

Neutralization Reaction
• It is the interaction of an acid and a base to
form a salt and water.
• This reaction is important for maintaining a
constant pH in the body.
• Buffers helps in maintaining pH.
 It releases H+ ions when the fluid is too basic
 It takes up H+ ions when fluid is too acidic

Carbonic acid-hydrogen bicarbonate buffer
system
• This is an important buffer system in the body.
• The pairing of carbonic acid and hydrogen bicarbonate ion
allows a reaction which occurs in both directions.
• It allows hydrogen to be released or taken up depending upon
the conditions in the blood.

Oxidation-Reduction reaction
• This reaction involves the transfer of electrons
 Oxidation = loss of electrons
 Reduction = gain of electrons
• Electrons are very reactive
• If oxidation occurs to one molecule, reduction
must also immediately occurs to the other
molecule
• This reaction is called a REDOX Reaction

Redox reactions in biology
Cellular respiration is an example of redox
reaction
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
In this reaction
Glucose molecule is oxidised to carbondioxide
Oxygen is reduced to water.

Condensation Reaction
• This reaction is also called Dehydration synthesis.
• This reaction is involved in the formation of all
the four types of macromolecles.
• In this reaction,
H-atom is removed from a functional group of one
molecule and an OH group is removed from another
molecule
This reaction releases water along with the formation
of product

Condensation reaction in Biology
• Two amino acids form peptide bond by condensation reaction
• In this reaction,
 Peptide bond is formed which is represented in red colour
 Water molecule is also released which is represented in
blue colour

Hydrolysis Reaction
• This reaction helps in the breakdown of
macromolecules into their monomers.
Water is added to break the bonds between
monomers.
WATER gets IN, MONOMER gets OUT
Hydrogen from the water is added to one
monomer, and the OH group is added to the
adjacent monomer.
Covalent bond between the macromolecule breaks
down to form two monomers.

Hydrolysis reaction in biology
• Phosphatases break the oxygen‐phosphorus bond of
phosphate esters:
• Other hydrolases function as digestive enzymes, for
example, by breaking the peptide bonds in proteins.

Group transfer reactions
• In this reactions functional groups move from one molecule to another.
• The enzymes involved are called transferases
• For example, alanine aminotransferase shuffles the alpha‐amino group
between alanine and aspartate:
• Other transferases move phosphate groups between ATP and other
compounds, sugar residues to form disaccharides, and so on.

Reactions involved in formation or removal
of a double bond with group transfer
• The functional groups are transferred by the
lyase enzymes which include amino groups,
water, and ammonia.
• For example - Deaminases remove ammonia in
the process of removal of amino groups from
amino acids.

Isomerization Reaction
• In this reaction, the position of a functional group is
changed within a molecule.
• Here, the molecule itself contains the same number
and kind of atoms that it did in the beginning.
• The enzyme, isomerases carry out these
rearrangements.
• Example –
(Enzyme – triose phosphate
isomerase)

Reactions involved in single bond formation
by eliminating the elements of water
• In this reactions, water
molecule is removed from
two functional groups to form
a single bond.
• The enzyme, ligases carry out
the reactions.
• For example,
aminoacyl‐transfer RNA
synthetases join amino acids
to their respective transfer
RNAs in preparation for
protein synthesis

Conclusion
• Trillions of chemical reactions happen simultaneously in the
body. They lead the processes that keep a human body
‘alive’.
• They are collectively known as metabolism.
• Metabolism is made up of numerous metabolic pathways.
• A metabolic pathway is a sequence of chemical reactions
that follow a set of ‘instructions’ contained in the body’s
DNA.
• Enzymes are biochemical catalysts that alter the rate of
reactions. However, unlike most chemical catalysts,
enzymes are highly selective and only promote specific
reactions.