A researcher measured the concentration of iodide ions in seawater and inside the cells of the brown alga kelp (Laminaria digitata). The table below displays the results of this investigation.
| Location | Concentration of iodide ions (mmol/dm3mmol/dm^{3}mmol/dm3) |
|---|---|
| Surrounding seawater | 0.002 |
| Inside kelp cells | 34.0 |
Explain how iodide ions are absorbed by the cells of the kelp.
