This covers the enzyme section of Edexcel IGCSE Biology course section 1.1 Life processes

1. IGCSE Biology – 4BI0
MAKING SENSE OF
Copyright©2015HenryExham
Icons CC – The Pink Group
Copyright©2017HenryExham
Icons CC – The Pink Group

2. Copyright © 2015 Henry Exham
• Can you explain the role of enzymes as
biological catalysts and how they are used in
metabolic reactions?
• How can enzyme function be affected by
temperature?
• Can you describe a simple controlled
experiment to show how enzyme activity is
affected by temperature?
• How are enzymes affected by pH? (Separate science only)
1.1 Life Processes - Enzymes
Objectives
2

3. Copyright © 2015 Henry Exham
• All chemical reactions that happen in a cell are
controlled by enzymes.
• Enzymes are biological catalysts.
• This means they speed up the reaction and do
not get used up in the reaction.
• They are all proteins which are coded for by
genes.
• The function of enzymes is to catalyse
metabolic reactions.
3
1.1 Life Processes - Enzymes
What are enzymes?

4. Copyright © 2015 Henry Exham
4
1.1 Life Processes - Enzymes
What are enzymes?
• Our body temperature is 37oC
• This is quite a low temperature for reactions
to take place.
• Without enzymes the reactions in our bodies
would occur too slowly to support our body’s
needs.

5. Copyright © 2015 Henry Exham
5
1.1 Life Processes - Enzymes
How do enzymes work?
• Each enzyme has an active site.
• The molecule that it wants to help change is called
the substrate.
• The active site fits the substrate like a lock and a key.
SubstrateActive site

6. Copyright © 2015 Henry Exham
6
1.1 Life Processes - Enzymes
How do enzymes work?
Substrate enters active site1

7. Copyright © 2015 Henry Exham
7
1.1 Life Processes - Enzymes
How do enzymes work?
Substrate enters active site An enzyme-substrate complex forms1 2

8. Copyright © 2015 Henry Exham
8
1.1 Life Processes - Enzymes
How do enzymes work?
Substrate enters active site1 2
3

9. Copyright © 2015 Henry Exham
9
1.1 Life Processes - Enzymes
How do enzymes work?
Products form and leave active site
Reaction occurs
Substrate enters active site An enzyme-substrate complex forms1 2
34

10. Copyright © 2015 Henry Exham
10
1.1 Life Processes - Enzymes
Factors affecting enzymes
• Each enzyme has an optimum
temperature at which it works
best.
• Above this temp the shape of the
enzyme’s active site is changed
by the heat.
• The enzyme becomes
DENATURED and stops working.
0 1
0
2
0
3
0
4
0
5
0
6
0
7
0
Temperature (oC)
Rateofreaction

11. Copyright © 2015 Henry Exham
11
1.1 Life Processes - Enzymes
Factors affecting enzymes
• The optimum pH for most
enzymes is pH 7.
• Although enzymes in the
stomach can work at pH 2.
pH
5 6 7 8 9
Rateofreaction
This slide is for separate
science only

12. Copyright © 2015 Henry Exham
12
1.1 Life Processes - Enzymes
Factors affecting enzymes
Can you describe a simple controlled experiment to
show how enzyme activity is affected by
temperature?
• Amylase is a good enzyme to investigate.
• It is used in digestion to breakdown the starch
you eat into sugar.
• You can test for starch using iodine.
• If there is starch present the solution will
change colour from the initial brown/yellow
colour to blue/black.

13. Copyright © 2015 Henry Exham
13
1.1 Life Processes - Enzymes
Factors affecting enzymes

14. Copyright © 2015 Henry Exham
14
1.1 Life Processes - Enzymes
Factors affecting enzymes

15. Copyright © 2015 Henry Exham
15
1.1 Life Processes - Enzymes
Factors affecting enzymes
• Choose five temperatures to investigate in the range of 10oC to
80oC.
• Repeat the same procedure for each temperature making sure
that all other variables are kept constant between each
experiment.
• For a control experiment you could use boiled amylase instead
of normal amylase.
• To make the experiment more reliable repeat each temperature
3 - 5 times and take the average time.
• Plot the results as a graph of temperature on the x-axis against
time on the y-axis.

16. This PowerPoint is protected under copyright.
It is designed for educational use. Either personal study or to be
presented to a class. It may be edited or duplicated for these
purposes only.
It must not be shared or distributed online in any format.
Some images used are under a separate creative commons license,
these are clearly marked.
Copyright © 2017 Henry Exham
Brought to you by MrExham.com
TERMS AND CONDITIONS
16