A technician kept equal samples of stomach protease for 10 minutes at different temperatures. The technician then brought every sample to 25 °C and added each one to an identical protein suspension at pH 2.
The suspension became clear when the protein had been digested.
| Temperature used before the test (°C) | Time taken for the suspension to become clear at 25 °C |
|---|---|
| 5 | 7.8 minutes |
| 40 | 8.0 minutes |
| 70 | Still cloudy after 30 minutes |
Which conclusion can be drawn from the results after all three samples were brought to 25 °C?
Keeping the protease at 5 °C permanently changed the shape of its active site.
Cooling the sample from 70 °C restored the original shape of its active site.
The protease works fastest when the reaction temperature is 40 °C.
Heating the sample to 70 °C denatured the protease by changing its active site.
304 exam-style questions on AQA GCSE Biology 2.2 Animal tissues, organs and organ systems, covering 2.2.1 The human digestive system, 2.2.2 The heart and blood vessels, 2.2.3 Blood, 2.2.4 Coronary heart disease: a non-communicable disease, 2.2.5 Health issues, 2.2.6 The effect of lifestyle on some non-communicable diseases, and 2.2.7 Cancer. Each one has a worked solution and a mark scheme showing where the marks go.