A scientist investigates the uptake of mineral ion Q by a freshwater single-celled organism.
At the start of each investigation, the concentration of ion Q is 1.2 mmol dm-3 in the surrounding water and 6.0 mmol dm-3 in the cytoplasm.
The table shows the results for three samples of the organism.
| Sample | Treatment | Oxygen concentration during measurement in %\%% | Rate of uptake of ion Q in arbitrary units |
|---|---|---|---|
| A | Kept at 20% oxygen | 20 | 14 |
| B | Kept at 0% oxygen for 30 minutes | 0 | 0 |
| C | Kept at 0% oxygen for 30 minutes, then returned to 20% oxygen | 20 | 13 |
Explain what the results suggest about how the cells take up ion Q.
A fourth sample has a concentration of ion Q of 6.0 mmol dm-3 in its cytoplasm. It is placed in water containing 8.0 mmol dm-3 of ion Q at 0% oxygen. The cell membrane contains open protein channels for ion Q.
Predict whether there will be net uptake of ion Q. Explain your answer.
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.