Student Worksheet
Investigating the action of pH on catalase activity
P5: Investigate the factors which affect the enzyme rate of reaction
D3: Explain why enzyme activity is affected by pH
Objective
 To determine the effect of pH on the rate of catalase
activity
Safety
 Eye protection must be worn.
Procedure
1. Set up nine inverted 100 cm3 measuring cylinders by
filling with water and inverting in a large beaker.
2. Insert the delivery tube into the open end of the
measuring cylinder under water.
3. Label five tubes with the pH buffers 3, 4, 5, 6, 7, 8, 9,
10 and 11 and add 1 cm3 of pH buffer to the
appropriately-labelled tube using a clean1 cm3 syringe
each time.
4. Now add 10 cm3 of hydrogen peroxide to each tube.
5. Using a clean 10 cm3 syringe, quickly add 1 cm3 of the
enzyme (catalase) to each tube and insert the rubber
bung and side-arm delivery tube. Start the stopwatch. It
is important to do this step as quickly as possible.
6. The other end of each delivery tube should be
completely under the inverted measuring cylinder.
7. Time the gas given off for 15 minutes and then read the
volume of gas collected for each tube.
8. Record your results in a table.
9. Plot a suitable graph of rate of reaction against pH.
From the examiner
 pH is a measure of the concentration of hydrogen ions
present in a solution.
 Enzymes are affected by changes in pH since the
hydrogen ions disrupt the hydrogen bonds and ionic
bonds that hold the tertiary structure of the active site
in place. This causes the active site to change shape
and substrate molecules no longer fit.
Equipment/materials
 Catalase solution
 10 vol Hydrogen peroxide
 Distilled water
 Five test tubes with rubber bungs to fit with
connecting tubes to a delivery tube
 Nine 100 cm3 measuring cylinders
 Nine large beakers to act as water troughs
 Two 10 cm3 syringes
 Nine 1 cm3 syringes
 Stopwatch
 pH buffers
 Small beaker and paper towel for rinsing syringes
 Labels/Chinagraph pencil/OHP pen
Diagram
Results/conclusion
Questions
1. Explain why changes in pH alter the rate of an enzyme-controlled reaction.
2. Using your biological knowledge, explain why different enzymes are affected by pH changes in different ways.
3. Identify any anomalous results and explain why you have these anomalies.
4. What are the main limitations of this procedure and how will these affect the data?
5. How could you reduce the limitations and improve the accuracy of the data?
OBSERVATION RECORD
Learner name:
Qualification:
Unit number & title:
Assignment title
BTEC Level 3 Subsidiary Diploma in Applied Science
(Applied Biology)
Unit 13: Biochemistry and Biochemical Techniques
13.3: Factors affecting enzyme activity
Description of activity undertaken
Students to carry out an investigation using hydrogen peroxide and catalase to
investigate the effect of pH on the rate of an enzyme controlled reaction.
Assessment criteria targeted
Task 2
P5: Investigate the factors which affect the enzyme rate of reaction
D3: Explain why enzyme activity is affected by pH
How the activity covers the requirements of the assessment criteria (this does not
confirm achievement of assessment criteria or confer an assessment decision)
Learner correctly carries out the investigation.
Learner to correctly collect the oxygen gas.
Learner to correctly produce a graph of the results
Learner to correctly explain the effect of pH on the enzyme catalase.
Learner to answer the questions on the sheet
Learner to work safely at all times
Learner name:
Learner
signature:
Assessor name:
Assessor
signature:
Date:
Mrs N Turner-Smith
Date: