Two enzymes, X and Y, catalyse the breakdown of the same substrate. Equal enzyme concentrations are tested with excess substrate.
Table
| pH | Temperature / ∘C^{\circ}\mathrm{C}∘C | Initial rate with X / arbitrary units | Initial rate with Y / arbitrary units |
|---|---|---|---|
| 5 | 20 | 4 | 7 |
| 5 | 40 | 12 | 3 |
| 8 | 20 | 2 | 9 |
| 8 | 40 | 6 | 5 |
Which conclusion applies at both pH values tested?
Warming from 20 ∘C20\,^{\circ}\mathrm{C}20∘C to 40 ∘C40\,^{\circ}\mathrm{C}40∘C decreases X activity but increases Y activity.
Warming from 20 ∘C20\,^{\circ}\mathrm{C}20∘C to 40 ∘C40\,^{\circ}\mathrm{C}40∘C increases both activities by the same proportion.
Warming from 20 ∘C20\,^{\circ}\mathrm{C}20∘C to 40 ∘C40\,^{\circ}\mathrm{C}40∘C decreases both activities by the same proportion.
Warming from 20 ∘C20\,^{\circ}\mathrm{C}20∘C to 40 ∘C40\,^{\circ}\mathrm{C}40∘C increases X activity but decreases Y activity.
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.