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Chemicals in Medicine
Chemical substances used for the treatment Definitions
of diseases and to reduce the suffering from pain
are called medicines or drugs. A medicine is a A medicine is a chemical
chemical substance that cures the disease and substance which cures the
is not only safe to use but also not cause any disease, is safe to use, has
addiction or much toxicity while a drug cures negligible toxicity and drug is a
disease and may cause side effects and creates chemical substance which also
addition etc. e.g., Penicillin is a medicine while cures the disease but is habit
Heroin is a drug. forming, causes addiction and
has serious side effects.
Drug — Target interaction
y Proteins which act as biological catalysts in
the body are called enzymes.
y Proteins which are crucial to communication
system in the body are called receptors.
y Proteins which carry polar molecules across
the membrances are called carrier proteins. Concept Ladder
(1) Enzymes as Drug Targets
The drugs in our body can
(i) Catalytic action of enzymes
be administrated by oral,
y The substrate molecules bind to the amino
intravenous injections
acid residues of the protein present on the
which is determined by
active site of the enzyme through a variety
the physical and chemical
of interactions such as hydrogen bonding,
properties and the site of
dipole-dipole interactions, van der Waals
desired action.
interactions and ionic bonding. These binding
forces should be strong enough to hold the
substrate long enough so that the enzyme
can catalyse the reaction, but weak enough
to allow the products to depart after their
formation.
Chemistry in Everyday Life
1.
, y The function of the enzyme is to provide
functional groups which will attack the
substrate to carry out the chemical reaction.
y This function is carie out by some other
amino acid residues of protein present on
the active site of the enzyme. These provide
free amino groups to attack the substrate and
bring about chemical reaction. Concept Ladder
y If the amino acid serine is present nearby the
substrate held on the active site, then its –
If the bond formed
OH group is free to act as a nucleophile in the
between an enzyme and
enzyme catalysed reaction.
the drug (inhibitor) is a
y Similarly, the functional groups such as –SH strong covalent bond
of L-cystein, –COOH of L-aspartic acid, phenyl which cannot be broken
ring of L-phenylalamine and heterocyclic ring easily, then the enzyme is
of L-histidine can participate as nucleophile blocked permanently. The
in enzyme catalysed reactions. body then degrades the
(ii) Drug-enzyme interaction enzyme drug (inhibitor)
Drugs which inhibit any of the two activities complex and synthesizes
of the enzymes are called enzyme inhibitors. the new enzyme.
Enzyme inhibitors can block the binding
site theregby preventing the binding of
the substrate to the active site and hence
inhibiting the catalytic activity of the enzyme.
y Drugs which compete with natural substrate
for their attachment on the acitve sites of
enzymes are called competitive inhibitors.
Chemistry in Everyday Life
2.
,y Some drugs, however, do not bind to the
active site but bind to a different site of the
Rack your Brain
enzyme which is called allosteric site. This
binding of the drug at allosteric site changes
the shape of the active site of the enzyme in Why do drugs reach Specific
such a way that the natural substrate cannot Targets?
recognize it. Such drugs are called non-
competitive inhibitors.
(2) Receptors as Drug Targets Concept Ladder
For communication system in the body,
The bond formed between
receptors are proteins which are crucial to
an enzyme and the drug
it. Majority of receptors are embedded in cell
(inhibitor) is a strong
membranes in such a wayOO that their small
covalent bond which
part possessing the active site projects out of
cannot be broken easily,
the surface of the membrane and opens on
then the enzyme is blocked
the outside region of the cell membrane.
permanently.
Chemistry in Everyday Life
3.
, Chemical Messengers
On the binding site of the receptor protein, Definitions
these chemical messengers are received. The
shape of the receptor protein changes a little for The message between two
accommodation of these chemical messengers, neurons or that between neurons
and it gives the message to the cell without and muscles is communicated
even entering the cell. After the transfer of the through certain chemical
message, the chemical messenger departs and substances called chemical
the active site of the receptor protein returns to messengers.
its original shape.
Types of chemical messengers
(i) Hormones
(ii) Neurotransmitters
(i) Hormones
They are the group of biomolecules which are
generated in the ductless (endocrine) glands.
These enter the blood stream and travel to
different parts of the body activating all the
receptors which recognise them for message Definitions
transfer. They are not deactivated very quickly.
Adrenaline (epinephrine) is an example of a The chemical substances which
Chemistry in Everyday Life
hormone. It is released from adrenal medulla suppress the action of hormones
in situations of stress or danger. It prepares that promote pregnancy are
the body (animals or humans) for physical called antifertility drug. These are
exercise to bear the stress. actually synthetic hormones.
4.
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