Introduction to Biochemistry: Dr.
Shakeel Sheikh(LUMHS)
Introduction to Biochemistry
Dr.Shakeel Sheikh
Lecturer, Biochemistry,
LUMHS,Jamshoro
compujin@gmail.com
Definition: Biochemistry is defined as study of chemical reactions that occur in living organisms
which include smallest forms of life as bacteria and viruses as well as highly complex, organized
forms of life such as human beings.
-It is also known as chemistry of biology, physiological chemistry, or chemistry of life.
-Life is the perpetual existence of chemical reactions as a result of which we are able to think,
work, develop and reproduce. Life disappears when these reactions cease to occur. So study of
biochemistry means study of life, its origin, chemical composition as well as structure of living
organism and their functions.
-The major objective of biochemistry is complete understanding at molecular level of all the
chemical processes associated with living cells.
-Because life depends on biochemical reactions, biochemistry can be called as basic language of
all biological sciences.
-It attempts to describe in molecular terms, the structures, mechanisms and chemical processes
shared by all living organisms.
-Biochemistry is a relatively young science in Pakistan but in the developed countries of the
world it has established its place in scientific, medical education and research.
Impact of Biochemistry on Medicine:
Biochemistry influences medicine in three ways:
A. It explains the cause of most of disease: for example consider the normal utilization of
glucose by the human beings.
Normally, GlucoseCO2 + H2O
Abnormal Condition
{Diabetes Mellitus}
Glucose in Urine
In normal conditions the glucose in converted to CO 2, H2O & energy in presence of
enzymes. But because of inactivation or inhibition of enzymes d/t any reason, man is
unable to metabolize glucose & an abnormal condition called diabetes mellitus results.
This whole process is only understandable by acquiring proper knowledge of
biochemistry. Today, by an expanding knowledge of biochemistry, we are able to
explain the cause of several diseases on molecular level.
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Introduction to Biochemistry: Dr.Shakeel Sheikh(LUMHS)
B. Diagnosis of a Disease: Diagnosis of a disease is a first step in the management of
disease. The applied part of the knowledge of biochemistry constitutes the major part of
diagnostic techniques & tests. These tests are in practical use in clinical laboratories to
determine abnormal metabolic products in blood, urine & other biological fluids. Other
biochemical tests like liver function tests (LFTs), renal function tests (RFTs),
determination of cardiac enzymes etc give valuable information to ascertain a disease &
to assess the function of various organs & their recovery rate from diseases.
C. Treatment of a Disease: The structural formulae of various biomolecules are thought to
be unwanted assignment by medical students. Here only one example of its importance
is mentioned. We study structural formulae of biomolecules to know how various atoms
in a molecule are arranged & linked to each other. One of such compounds is Xanthine
which is formed from adenosine & guanosine in our body. Normally xanthine is
converted to uric acid, but in abnormal conditions more uric acid is formed than normal
& it gets deposited in joints causing painful condition known as Gouty Arthritis. By
studying the structure of xanthine, an artificial compound (Allupurinol) resembling to
the structure of xanthine has been synthesized. When this compound is given to the
patient of gouty arthritis, an enzyme known as xanthine oxidase combines with
allupurinol, so xanthine is saved from conversion to uric acid & symptoms of gouty
arthritis. Only the study of structure of xanthine leads to the synthesis of a similar
compound i.e. allupurinol had made it possible to treat the disease on molecular basis.
In this way biochemistry directly influences medicine & numerous disease have been
successfully treated.
Biochemical compounds:
Living organisms should be able to transform matter and energy into different forms, show
response to changes in their environment and show growth and reproduction. All living
organisms undergo changes due to large organic compounds called macromolecules. Four main
types of macromolecules control all activities.There are four major classes of biochemical
compounds:
1. Carbohydrates They are polyhydroxy aldehydes or ketones or can be converted to
such compounds on appropriate treatment. They are also known as saccharides and a
general formula Cn(H2O)n represents most of the carbohydrates.
2. Lipids They are organic non-polar compounds that are totally or nearly insoluble in
water but quite soluble in organic solvents like ether, chloroform or benzene. They are
esters of fatty acids or substances capable of forming such esters. They are present in
plans as well as in animals.
3. Proteins They are most abundant & functionally diverse molecules in living systems.
Virtually every life process depends on this class of molecules. For example, enzymes &
polypeptide hormones direct & regulate metabolism in the body where as contractile
proteins in muscle permit movement. All proteins are composed of amino acids which
are connected by a peptide bond.
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Introduction to Biochemistry: Dr.Shakeel Sheikh(LUMHS)
4. Nucleic acids 2 types; DNA & RNA. They are basically required for the transmission,
storage & expression of genetic information.
Major types of Biochemical Reactions:
The major biochemical reactions are:
1. Oxidation: Oxidation is the loss of electrons.
2. Reduction: Reduction is the gain of electrons.
3. Hydrolysis: It is a chemical process in which a molecule is cleaved into two parts by the
addition of a water molecule.
4. Phosphorylation: Addition of phosphate group to a molecule.
5. Phosphorolysis: Splitting of a bond by the addition of phosphoric acid to a compound.
6. Decarboxylation: It is the loss of carbon dioxide.
7. Deamination: It is the removal of amino group.
8. Transamination: It is the transfer of amino group from one molecule to another.
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