Equal enzyme samples are kept at different pH values for five minutes. Each sample is then adjusted to pH 7 and tested with fresh substrate at the same temperature.
Table
| pH during the five-minute treatment | Initial rate when tested at pH 7 / arbitrary units |
|---|---|
| 2 | 1 |
| 7 | 10 |
| 12 | 0 |
Which conclusion is best supported?
Extreme pH treatments caused a loss of activity that was not fully reversed at pH 7.
Extreme pH treatments used up the fresh substrate before the activity tests began.
The enzyme has its optimum pH at 2 because some activity remained after treatment.
The enzyme has its optimum pH at 12 because no activity remained after treatment.
44 exam-style questions on Edexcel GCSE Biology 1.3 Enzymes, covering 1.3.1 Mechanism of enzyme action, 1.3.2 Denaturation of enzymes, 1.3.3 Factors affecting enzyme activity, and 1.3.4 Measuring energy in food by calorimetry. Each one has a worked solution and a mark scheme showing where the marks go.