A student investigated the effect of temperature on the rate of urea breakdown by the enzyme urease. The reaction produces ammonia, which increases the pH of the solution.
The student used the following method:
Table 1 shows the student's results at 25 ∘C25\text{ }^{\circ}\text{C}25 ∘C:
| Time (hours) | 0 | 1 | 2 | 3 | 4 | 5 |
|---|---|---|---|---|---|---|
| pH | 6.0 | 6.2 | 6.9 | 7.8 | 8.3 | 8.4 |
How could the student keep the reaction mixture at a constant temperature for the duration of the 5-hour experiment?
Identify one variable, other than temperature, that the student should keep constant.
Use the data in Table 1 to calculate the mean rate of change in pH per hour between 1 hour1\text{ hour}1 hour and 4 hours4\text{ hours}4 hours. Show your working.
If the experiment is repeated at 35 ∘C35\text{ }^{\circ}\text{C}35 ∘C (which is below the enzyme's denaturation temperature), describe two expected features of the pH curve compared to the 25 ∘C25\text{ }^{\circ}\text{C}25 ∘C curve.
Practise AQA GCSE Biology Respiration with exam-style questions for Foundation and Higher tier. 16 questions covering Aerobic and anaerobic respiration, Response to exercise, and Metabolism, matched to the AQA GCSE Biology (8461) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.