ENZYME ACTION –
MEASURING RATE OF
REACTION – SUBSTRATE
CONCENTRATION
The effects of the following factors on the rate of
enzyme controlled reactions – enzyme
concentration, substrate concentration, concentration
of competitive and of noncompetitive inhibitors, pH
and temperature.
Do now: Exam Question
Explain the current model of
enzyme action and outline
how have models of enzyme
action developed.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how enzymes
catalyse reactions by
lowering activation
energy
- Outline a method for
measuring enzyme
action in a reaction.
- Analyse results from
the substrate rate
graph and explain
conclusions linking
back to the enzyme
substrate model.
Activation energy




Chemical reactions require a certain
amount of energy to start.
This is called the Activation energy.
Enzymes lower the activation energy
needed for a reaction to happen. This
means that a reaction can happen with
less energy input and so reactions will
happen quicker.
We call them biological catalysts
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how enzymes
catalyse reactions by
lowering activation
energy
- Outline a method for
measuring enzyme
action in a reaction.
- Analyse results from
the substrate rate
graph and explain
conclusions linking
back to the enzyme
substrate model.
How to measure reaction
speed?
Howcould
couldyou
you measure
measure the
How
the rate
progress
of afor
reaction?
of
reaction
these enzyme
 Record
the dependent
variable
controlled
reactions:

1) A reaction that breaks down
water into Hydrogen and
 How could you measure how fast
oxygen gases
a reaction
is that
happening?
2)A
reaction
produces heat
 Record
the dependent
variable
the more
products
made.
every-time
you change
3)
A reaction
that the
makes
independent
variable.
products
that
change colour.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how enzymes
catalyse reactions by
lowering activation
energy
- Outline a method for
measuring enzyme
action in a reaction.
- Analyse results from
the substrate rate
graph and explain
conclusions linking
back to the enzyme
substrate model.
Effect of enzyme concentration
on rate of reaction

What is the relationship shown
in the graph?
 Link
back to active sites?
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how enzymes
catalyse reactions by
lowering activation
energy
- Outline a method for
measuring enzyme
action in a reaction.
- Analyse results from
the substrate rate
graph and explain
conclusions linking
back to the enzyme
substrate model.
In which of these will the
rate of reaction be fastest?

Why would not adding anymore
substrate make the reaction
faster?
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how enzymes
catalyse reactions by
lowering activation
energy
- Outline a method for
measuring enzyme
action in a reaction.
- Analyse results from
the substrate rate
graph and explain
conclusions linking
back to the enzyme
substrate model.
Enzyme controlled reactions -Outcomes:
- Recall enzyme
substrate concentration
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how enzymes
catalyse reactions by
lowering activation
energy
- Outline a method for
measuring enzyme
action in a reaction.
- Analyse results from
the substrate rate
graph and explain
conclusions linking
back to the enzyme
substrate model.
ENZYME ACTION –
MEASURING RATE OF
REACTION – TEMPERATURE
AND PH
The effects of the following factors on the rate of
enzyme controlled reactions – enzyme
concentration, substrate concentration, concentration
of competitive and of noncompetitive inhibitors, pH
and temperature.
Do now: Enzyme rates and
temperature

Look at this enzyme rate graph.
Explain the different phases of
each part. Link this back to GCSE
knowledge and A-level knowledge
3
1
2
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Describe the term
denaturing relating
back to active site and
enzyme substrate
complexes.
- Analyse results from
the rate graph and
explain conclusions
linking back to the
protein structure and
the enzyme-substrate
model.
Effect of temperature on
rate of reaction.



Most enzyme controlled reactions
require an optimum temperature
of 37 degrees celsius.
If lower than this….. And so the
rate of these reactions is slower.
If higher than this…. And so the
rate of these reactions are slower.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Describe the term
denaturing relating
back to active site and
enzyme substrate
complexes.
- Analyse results from
the rate graph and
explain conclusions
linking back to the
protein structure and
the enzyme-substrate
model.
Denaturing of Enzymes

Why is the shape of the enzyme
so important to its function?
 The
substrate has a complimentary
shape that fits exactly into the
enzyme so the reaction can happen.

What determines the
enzymes/proteins specific shape?
 The
primary, secondary, tertiary
and quaternary structures.

What would happen if the shape
of the enzyme changed?
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Describe the term
denaturing relating
back to active site and
enzyme substrate
complexes.
- Analyse results from
the rate graph and
explain conclusions
linking back to the
protein structure and
the enzyme-substrate
model.
Denaturing of Enzymes

Denaturisation – when the
enzymes active site changes
shape and deforms.
 The
substrate is no longer
complimentary
 The complex cannot form and the
reaction cannot happen

Why does rate of reaction not
just drop to zero after 37
degrees?
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Describe the term
denaturing relating
back to active site and
enzyme substrate
complexes.
- Analyse results from
the rate graph and
explain conclusions
linking back to the
protein structure and
the enzyme-substrate
model.
pH and rates of
reaction


Acids contain high amounts of
H+ ions
Alkalis have high amounts of
OH- ions
 These
can interfere with the
structure of the active site and
denature the enzymes
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Describe the
relationships between
temperature and rate
of reaction and pH.
- Describe the term
denaturing relating
back to active site and
enzyme substrate
complexes.
- Analyse results from
the rate graph and
explain conclusions
linking back to the
protein structure and
the enzyme-substrate
model.
ENZYME ACTION INHIBITORS
The effects of the following factors on the rate of
enzyme controlled reactions – enzyme
concentration, substrate concentration, concentration
of competitive and of noncompetitive inhibitors, pH
and temperature.
Do now:
Long answer question:
Explain the importance of protein
structure in enzyme function and
how different factors can affect this.

Mini – Practical:
1)
Add the catalase to the hydrogen
peroxide, measure how much oxygen
is produced in a minute.
2)
To the catalase, add 20mls of copper
sulphate solution, leave for 3 minutes.
Now add the hydrogen peroxide and
measure in a minute.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how
competitive inhibitors
decrease enzyme
action linking to
terms active site and
complementary
shape.
- Explain how noncompetitive inhibition
reduces enzyme
action by attachment
to allosteric site.
- Apply knowledge of
inhibition to explain
some negative
feedback mechanisms.
Inhibitors
Chemicals that bind to an enzyme
and reduce its activity.

Competitive Inhibitors
 Bind
to the active site just like a
substrate would

Non competitive inhibitors.
 Bind
to the allosteric site
permanantly and denature the
active site.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how
competitive inhibitors
decrease enzyme
action linking to
terms active site and
complementary
shape.
- Explain how noncompetitive inhibition
reduces enzyme
action by attachment
to allosteric site.
- Apply knowledge of
inhibition to explain
some negative
feedback mechanisms.
Competitive Inhibitors



Have a complimentary shape just like a
substrate.
‘compete’ with the substrate to bind with the
enzyme.
When substrate concentration increases, the
inhibitors are less effective.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how
competitive inhibitors
decrease enzyme
action linking to
terms active site and
complementary
shape.
- Explain how noncompetitive inhibition
reduces enzyme
action by attachment
to allosteric site.
- Apply knowledge of
inhibition to explain
some negative
feedback mechanisms.
Competitive Inhibitors

Vmax value is the same for
normal enzyme and an enzyme
inhibited competitively.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how
competitive inhibitors
decrease enzyme
action linking to
terms active site and
complementary
shape.
- Explain how noncompetitive inhibition
reduces enzyme
action by attachment
to allosteric site.
- Apply knowledge of
inhibition to explain
some negative
feedback mechanisms.
Non- Competitive Inhibitors



The inhibitors bind at the allosteric site,
not the active site!
They cause the shape of the active site to
change (denature)
Substrates cant bind anymore, no matter
how much substrate you add.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how
competitive inhibitors
decrease enzyme
action linking to
terms active site and
complementary
shape.
- Explain how noncompetitive inhibition
reduces enzyme
action by attachment
to allosteric site.
- Apply knowledge of
inhibition to explain
some negative
feedback mechanisms.
Non- Competitive Inhibitors

The vmax is half of what a
normal enzyme reaction
would be.
Outcomes:
- Recall enzyme
structure and the
mechanism of the
enzyme substrate
complex.
- Explain how
competitive inhibitors
decrease enzyme
action linking to
terms active site and
complementary
shape.
- Explain how noncompetitive inhibition
reduces enzyme
action by attachment
to allosteric site.
- Apply knowledge of
inhibition to explain
some negative
feedback mechanisms.
Outcomes:
- Recall enzyme
structure and the
Enzyme Inhibition
mechanism of the
enzyme substrate
complex.
 What does negative feedback mean?
- Explain how
 The products of an enzyme reaction feedback
competitive inhibitors
and act as inhibitors for the enzyme to stop too
much reaction happening
decrease enzyme
action linking to
terms active site and
complementary
shape.
- Explain how noncompetitive inhibition
reduces enzyme
action by attachment
to allosteric site.
- Apply knowledge of
inhibition to explain
 In what process do you think this is important?
some negative
feedback mechanisms.
Negative feedback of