Biology 9700/51 — May/June 2020
Cambridge A-Level · Planning, Analysis and Evaluation · worked solutions for every part, with the mark scheme
Topics Planning · Analysis, Conclusions and Evaluation
Chlorella is a green, single-celled protoctist that is photosynthetic. Some students immobilised cells from a culture of this protoctist using the same method as used for immobilising enzymes.
Outline how the students could immobilise cells of Chlorella.
The students used the respirometer shown in Fig. 1.1 to measure oxygen uptake by the immobilised Chlorella cells.
The students used the respirometer to test the hypothesis:
The volume of oxygen taken up by respiration in immobilised Chlorella increases with an increase in temperature.
State the independent variable and the dependent variable in this investigation.
independent variable ______
dependent variable ______
The students decided to measure oxygen uptake for 5 minutes using a range of temperatures from to .
Discuss whether the range of temperatures used by the students was suitable for their investigation.
Describe a method by which the students could set up the respirometer and use it to test their hypothesis:
The volume of oxygen taken up by respiration in immobilised Chlorella increases with an increase in temperature.
Your method should be set out in a logical order and be detailed enough to let another person follow it.
Details of immobilising Chlorella are not required.
The students calculated the oxygen uptake for each temperature.
Their results are shown in Table 1.1.
Table 1.1
| temperature / | 10 | 20 | 30 | 40 | 50 |
|---|---|---|---|---|---|
| oxygen uptake / | 200 | 400 | 800 | 750 | 680 |
Outline how the students calculated the volume of oxygen uptake.
State and explain two conclusions about the trends shown by these results.
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