Proteins made
in cells and may
be intracellular
or extracellular.
Biological Catalysts that speed up the Rate of
Reaction. They are not used up in the
process. Particular Enzymes only catalysis a
particular reaction, so they are very specific.
They are Tertiary structure
Globular Proteins and
dependent on binds
formed between R groups.
Energy required to start a reaction is
called Activation Energy. Enzymes
lower this energy for a biological
reaction to proceed.
They don't always
break things
down, they can
put Substrates
together.
LOCK AND KEY HYPOTHESIS
The Active Site region on the Enzyme has a
complementary shape to the Substrate.
The Subsrate binds to
the Enzyme's Active
Site forming an
Enzymes-Substrate
Complex. The
reaction then takes
place and Products
are formed. Then the
Enzyme is used again
as it collides with an
other Substrate.
INDUCED FIT MODEL
The Substrate alters
the shape of the
Active Site on the
Enzyme when it binds.
IMMOBILISED ENZYMES
Fixed,
bound or
trapped
Enzymes in
an inert
Matrix
such as a
gel capsule.
Using Immobilised
Lactase to Hydrolise
Lactose in milk to
produce Glucose
and Galactose
(Lactose free Milk).
Used in Fermentation and Washing
Powders (encapsulate Enzyme in wax
if people are allergic).
Used also in making Baby
Food, Pectinases break down
Pectin in the cell walls of
fruit and vegetables.
Biosensors are Medical Devices that
measure concentration of a Specific
Metabolite within a mixture. When a mixture
is passed over the Enzymes, a reaction
occurs. Because Enzymes are specific to a
given Substarte, Glucose Biosensor is highly
accurate ast detecting Glucose levels, even
at low concentrations. Diabetics can use a
Glucose Biosensor to test blood sugar levels.
Immobilised Enzymes can be re-used so are
cheaper than Free Enzymes. They can
tolerate a wide range of Conditions, like
higher temperatures and pHs. They can be
easily removed and added so there is more
control over the Rates of Reaction. More
than one Enzyme with a different Optima
can be used together. Product can be easily
recovered without contamination.
They have a slower Rate of
Reaction and Substrate
can only penetrate beads -
maybe surface Enzymes
only Catalyse reactions.
RATE OF REACTION
The Higher the Enzyme
Concentration, the more
likely for a successful
collision with a Substrate
(provided there is a high
concentration of
Substrate). Until all
Substrate is used up and
the rate stays the same.
Higher the
Concentration of
Substrate, the more
successful collisions will
take place. Rate of
Enzyme Catalysed
reaction increases as
the concentration of
the Substrate increases
up to a maximum point
where the
concentration of
Enzymes is limiting, the
rate will then Plateau.
At low temperatures, Enzymes
are inactive so are few
Enzyme-Substrate Complexes. At
high temperatures, there is an
increase in kinetic energy so are
more successful collisions. This
occurs up until the Optimum
temperature has been reached.
Over the optimum temperature
of the Enzyme breaks the
Hydrogen bonds and the tertiary
structure changes, the Active
Site then changes as the Enzyme
has denatured and the
Substrate can no longer fit .
Most Enzymes are effective in a narrow pH range,
within this range, one particular pH will be the
optimum where the Enzyme works best. Any
change in pH decreases the rate of reaction.
Changes affect Ionic and Hydrogen bonds holding
the Enzyme's Tertiary Structre. Large changes
from the Optimum causes the Active Site to
change shape and denature and small changes
cause reversible changes in structure.
Competitive Inhibitors of a particular Enzyme is
complimentary to its Active Site so can block
the Substrate from binding. It can be overcome
by increasing the Concentration of Substrate. If
there is a higher Concentration of Inhibitor, the
rate will be reduced as more successful
collisions would occur between the Enzymes
and Inhibitor as it binds to the Active Site.
Non-Competitive Inhibitors is not
complimentary and doesn't bind to
the Active Site. It binds to the
Allosteric Site, but as it does, it
causes the Enzyme's Active Site to
change. So Substrates can no longer
fit. Even if Substrate Concentration
is high, the Inhibitor will still have
affect on the rate as the Optimum
rate will never be reached. The
Inhibitor can still successfully bind
to the Enzyme as it isn't competing
for the same site as the Substrate.