An enzyme is tested at several substrate concentrations. Temperature and pH are constant.
Table
| Substrate concentration / arbitrary units | Initial rate with enzyme concentration E / arbitrary units | Initial rate with enzyme concentration 2E / arbitrary units |
|---|---|---|
| 1 | 3 | 6 |
| 2 | 6 | 12 |
| 4 | 10 | 20 |
| 8 | 10 | 20 |
Which explanation is best supported by the results at substrate concentrations 4 and 8?
Active-site availability limits rate; doubling enzyme concentration doubles the maximum rate.
Substrate availability limits rate; doubling enzyme concentration doubles the maximum rate.
Active-site availability limits rate; doubling substrate concentration doubles the maximum rate.
Substrate availability limits rate; doubling substrate concentration doubles the maximum rate.
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.