A seabird removes excess sodium ions using salt glands. Cells in each gland move sodium ions from the blood into fluid in a duct.
| Location | Sodium ion concentration in mmol dm⁻³ |
|---|---|
| Blood around the gland cells | 145 |
| Fluid in the duct | 510 |
Scientists changed the rate of respiration in samples of gland cells and measured the rate of sodium ion transfer.
| Sample | Energy released by respiration in J g⁻¹ h⁻¹ | Rate of sodium ion transfer in µmol g⁻¹ h⁻¹ |
|---|---|---|
| P | 245 | 22.0 |
| Q | 128 | 11.7 |
| R | 64 | 6.1 |
Use the data to explain which sub-cellular structure is likely to be especially numerous in the gland cells.
140 exam-style questions on AQA GCSE Biology 1.3 Transport in cells, covering 1.3.1 Diffusion, 1.3.2 Osmosis, and 1.3.3 Active transport. Each one has a worked solution and a mark scheme showing where the marks go.