The table shows the concentration of potassium ions and sulfate ions inside a unicellular freshwater alga cell and in the pond water.
| Place | Ion concentration in mg per dm3\text{mg per dm}^3mg per dm3 (Potassium) | Ion concentration in mg per dm3\text{mg per dm}^3mg per dm3 (Sulfate) |
|---|---|---|
| In the alga cell | 3150 | 1568 |
| In the pond water | 45 | 14 |
The ratio for the concentration of potassium ions in the alga cell compared to the pond water is 70:170:170:1. Calculate the ratio for the concentration of sulfate ions in the alga cell compared to the pond water.
During a hot summer, a thick layer of floating duckweed covers the pond, reducing the concentration of dissolved oxygen in the water. Suggest why this prevents the alga cells from absorbing potassium or sulfate ions.
Complete the table below by naming a biological molecule that is made in plants using each of the mineral ions.
| Mineral ion | Molecule made using the mineral ion |
|---|---|
| phosphate | |
| magnesium |
23 exam-style questions on Edexcel IGCSE Biology Movement of substances into and out of cells. Each one has a worked solution and a mark scheme showing where the marks go.