Sections of small intestine are placed in solutions containing potassium ions. The concentration of potassium ions inside the cells lining the intestine is higher than the concentration in the solution outside the cells.
The sections are exposed to solutions with different oxygen concentrations. The mass of tissue, temperature, potassium-ion concentration and volume of solution are kept the same for each section.
Measurements of potassium-ion uptake are recorded below.
| Oxygen concentration in the solution in %\%% | Rate of potassium-ion uptake in arbitrary units |
|---|---|
| 0 | 0.0 |
| 4 | 6.4 |
| 8 | 12.7 |
| 16 | 12.9 |
Explain the pattern in the results and predict the rate of potassium-ion uptake if the oxygen concentration was 12 %.
114 exam-style questions on OCR GCSE Biology 2.2 The challenges of size, covering 2.2.1 Exchange surfaces and surface area : volume ratio, 2.2.2 Substances transported in organisms, 2.2.3 The human circulatory system, 2.2.4 The heart and blood vessels, 2.2.5 Red blood cells and plasma, 2.2.6 Uptake of water and mineral ions by plants, 2.2.7 Transpiration and translocation, 2.2.8 Xylem and phloem, 2.2.9 Environmental factors and water uptake, and 2.2.10 Using a potometer. Each one has a worked solution and a mark scheme showing where the marks go.