A student measured the time taken for all of the starch in a mixture to be broken down by amylase at pH 7. The student repeated the measurement three times.
Table shows the student's results.
Table: The time taken for all of the starch in a mixture to be broken down by amylase at pH 7, in three repeats
| Repeat | Time taken for all of the starch to be broken down in s |
|---|---|
| 1 | 84 |
| 2 | 90 |
| 3 | 96 |
Calculate the mean time taken.
At pH 4, the mean time taken was 180 s.
Suggest why amylase breaks down starch more slowly at pH 4 than at pH 7.
Give one reason why the student repeated the measurement three times.
The student used the same volume and concentration of starch solution in every test.
Explain why.
179 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.