A student investigates enzyme activity. Each reaction contains the same enzyme concentration and starts with the same substrate concentration.
Table
| Reaction | pH | Temperature / ∘C^{\circ}\mathrm{C}∘C | Initial rate / arbitrary units |
|---|---|---|---|
| P | 5 | 20 | 4 |
| Q | 5 | 30 | 8 |
| R | 7 | 30 | 12 |
| S | 7 | 40 | 10 |
Which conclusion is supported by a comparison in which only one variable changes?
Changing pH from 5 to 7 at 30 ∘C30\,^{\circ}\mathrm{C}30∘C increases rate by 50%50\%50%.
Changing pH from 5 to 7 at 20 ∘C20\,^{\circ}\mathrm{C}20∘C increases rate by 200%200\%200%.
Changing temperature from 20 ∘C20\,^{\circ}\mathrm{C}20∘C to 40 ∘C40\,^{\circ}\mathrm{C}40∘C doubles the rate at pH 5.
Changing temperature from 20 ∘C20\,^{\circ}\mathrm{C}20∘C to 30 ∘C30\,^{\circ}\mathrm{C}30∘C triples the rate at pH 7.
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.