Living organisms are living only because of the uncountable number of chemical reactions that are continuously going on in them for keeping them alive and active. These chemical reactions are of various types and all these have been presented in this presentation.

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

2. 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.

3. 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

4. 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

5. 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

6. 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

7. 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.

8. 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

9. 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.

10. 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

11. 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

12. 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.

13. 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.

14. 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.

15. 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.

16. 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)

17. 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

18. 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.