A scientist measures the rate of uptake of potassium ions by plant roots at different concentrations of oxygen.
The table shows the results.
Table
| Concentration of oxygen in %\%% | Rate of uptake of potassium ions in arbitrary units |
|---|---|
| 0 | 2 |
| 5 | 10 |
| 10 | 18 |
| 15 | 22 |
| 20 | 22 |
Which conclusion is supported by the data?
Potassium ions are taken up only by diffusion, because uptake continues at 0%0\%0% oxygen.
The rate of uptake is directly proportional to oxygen concentration across the whole range.
Potassium ions stop being taken up above 15%15\%15% oxygen, because the rate stops increasing.
Uptake increases with oxygen up to 15%15\%15%, suggesting it uses energy from aerobic respiration.
194 exam-style questions on OCR GCSE Biology 2.1 Supplying the cell, covering 2.1.1 Transport across cell membranes, 2.1.2 Mitosis and the cell cycle, 2.1.3 Importance of cell differentiation, and 2.1.4 Stem cells. Each one has a worked solution and a mark scheme showing where the marks go.