5 minute poster
• In your groups you need to produce a poster
that summarises everything we found about
enzymes last lesson WITHOUT looking in your
book.
Enzymes and pH
• Lesson Learning Outcomes:
Recall that
enzymes
speed up
biological
reactions.
Describe the
process of
denaturing
Increasing Difficulty
Explain the
effects of pH
on an
enzyme
activity.
Factors affecting Enzymes
Make a list of any
factors you can
think of that might
affect the rate of
enzyme controlled
reactions
Enzyme and pH
Enzyme
Lipase (pancreas)
Lipase (stomach)
Lipase (castor oil)
Pepsin
Trypsin
Urease
Invertase
Maltase
Amylase (pancreas)
Amylase (malt)
Catalase
pH Optimum
8.0
4.0 - 5.0
4.7
1.5 - 1.6
7.8 - 8.7
7.0
4.5
6.1 - 6.8
6.7 - 7.0
4.6 - 5.2
7.0
Factors affecting enzymes
The rate of enzyme–catalyzed reactions depends on several factors. What are some
of these?
Factors that affect the rate of a reaction include:
 temperature
 substrate concentration
 pH
 surface area
 enzyme concentration
 pressure.
All enzymes work best at only one particular temperature and pH: this is called the
optimum.
Different enzymes have different optimum temperatures and pH values.
What happens at the active site?
In the same way that a key fits into a lock, so a substrate is thought to fit into an
enzyme’s active site. The enzyme is the lock, and the reactant is the key.
+
↔
enzyme
+
reactant
↔
↔
enzyme-reactant
complex
+
enzyme
↔
+
products
Glossary definition
Denaturing: When shape of an active
site changes as a result of bonds
within the enzyme breaking. This can
be caused by extreme temperatures or
pH’s
heat
pH
normal
denatured
Collect a mean
pH buffer in H2O2
3
4
5
7
8
9
Volume of foam
produced (cm3)
Analysis
• Can you draw a line graph of your
average results you have collected
for the catalase rate of reaction.
• Can you explain your graph in terms
of pH.
Past Questions
Anna is investigating the affect of temperature on enzyme activity.
1. Describe the lock and key model [2 marks]
2. Anna plots a graph to show the results of her experiment. Describe
what is happening at stages A, B, C and D. [4 marks]
3. What is the optimum temperature of the enzyme? [1 marks]
4. Explain the meaning of the term “denature” [2 marks]
5. Name two factors that can lead to an enzyme being denatured. [2
marks]
Question time
• In your groups of four each person needs to
come up with a question to ask another group
about enzymes and write it on your square of
your placemat.