Biology 5090/31 — May/June 2019
Cambridge O-Level · Practical Test · worked solutions for every part, with the mark scheme
Topics Observations and Measurements · Analysis, Conclusions and Evaluation · Planning Experiments and Investigations · Microscopy and Biological Drawing · Experimental Contexts · Use of Techniques, Apparatus and Materials
Catalase is an enzyme found in living cells. This enzyme catalyses the breakdown of hydrogen peroxide into oxygen and water. A suspension of yeast cells in water can be used as a source of catalase.
The oxygen produced is given off as gas and causes foam to form as shown in the diagram. The larger the volume of foam produced, the greater the activity of the catalase.
You are going to investigate the activity of the enzyme catalase.
You are provided with a suspension of yeast cells in water as your source of catalase, and some hydrogen peroxide solution.
Use the following method:
- use a stirring rod to stir the yeast suspension in the beaker
- use a syringe to add of yeast suspension to the measuring cylinder
- use a clean syringe to add of hydrogen peroxide solution to the measuring cylinder
- immediately start timing
- after 1 minute measure the total volume of the suspension, including any foam formed on top, and record this in the table
- repeat the measurement after every minute for 5 minutes, recording the results in the table.
| time / minutes | total volume of suspension and foam / |
|---|---|
| 0 | 10 |
| 1 | |
| 2 | |
| 3 | |
| 4 | |
| 5 |
On the grid provided, plot a line graph of the data in the table. Join the points with ruled lines.
Use the results to state the time period during which catalase activity was the greatest.
______
Describe the shape of the graph.
______
Suggest reasons for
- stirring the yeast suspension at the start of the experiment
______
- using different syringes for measuring the yeast suspension and the hydrogen peroxide solution.
______
Suggest a source of inaccuracy in the method for this experiment.
______
Design an experiment based on the method already described (see page 2) to investigate the effect of increasing temperature on the activity of catalase. Give full experimental details.
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