Enzymes part 01 l l Biomolecules LEC 05 l l class 11 biology

Enzymes
In tertiary structure of protein the
backbone of the protein chain folds
upon itself, the chain criss- cross itself
and hence , many cravices or pockets are
made. One such pocket is the active site.
Active site = crevice / pocket into which
substrate fits .
● Enzymes catalyse reactions at a
high rate .
Difference between inorganic
catalyst and enzymes
1. Inorganic catalysts work
efficiently at high temperatures
nd high pressure, while
enzymes get damaged at high
temperatures and pressure (
approximately above 40 °c ) .[
Exception enzymes isolated
from organisms like hot vents
and sulphur springs e.g. taq
polymerase] are stable and
retain their catalytic power
even at high temperatures (
upto 80-90°c ) . It is an
important quality of such
enzymes isolated from
thermophilic organisms.

How enzymes works
Chemical compounds undergo two
types of changes.
1. Physical change = change in shape
without breaking bonds / change in
state of matter e.g.  ➡water 
➡water vapour.
2. Chemical reaction: bond breaking
and bond formation occurs. E.g. CO2+ H20=H2Co3
Rate of reaction:
Amount of product formed per unit
time .
Rate = dp/ dt
Rate is also called velocity if direction
is specified.
The factors that influenced rate of
physical and chemical processes:
1. Temperature ( rate double or
decrease by half for every 10°c
change in either direction.)
2. Enzymes catalysed reaction rate
is higher than uncatalysed
reaction.
How do enzymes bring about
such high rates of chemical
conversions ?
1. Substrate: the chemical which
is converted into a product.
2. Products: the chemical that is
formed after enzymatic
reactions.
Steps of an enzymatic reactions
:
1 . Binding of substrate to the
active site of enzymes.
2.formation of enzyme-
substrate complex .
3. Formation of enzyme-
product complex .
4. Products
Factors affecting enzyme
activity:
1. Temperature: enzymes
generally function in a
narrow range of temperature. Enzyme show
its highest activity at a
particular temperature
called as optimum
temperature. Extreme high
and low temp both destroy
enzymatic activity.
2. pH : same as temperature.
3. Concentration of
substrate
4. Competitive inhibitors :
when the binding of the

chemicals shuts off enzyme
activity, the process is called
inhibition and the chemical
is called an inhibitor.
When the inhibitor closely
resembles the substrate in its
molecular structure and
inhibits the activity of the
enzyme it is known as
competitive inhibitor.
E.g.inhibition of succinate
dehydrogenase by malonate
which closely resembles the substrate succinate in
structure.
Competitive inhibitors are
often use in control of
bacterial pathogens.





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