A freshwater alga takes in nitrate ions from the water through its cell membrane.
At the start of an investigation, the nitrate ion concentration inside the algal cells was 6.0 mmol dm-3. The nitrate ion concentration in the surrounding water was 0.40 mmol dm-3.
The mean rate of nitrate ion uptake was measured under two conditions.
| Condition | Mean rate of nitrate ion uptake in pmol per 106 cells per minute\text{pmol per }10^6\text{ cells per minute}pmol per 106 cells per minute |
|---|---|
| Oxygen available | 36 |
| Oxygen unavailable | 0 |
Explain how the alga takes in nitrate ions. Use the data in your answer.
Oxygen remains available and nitrate ion uptake is initially occurring at the rate shown in the table.
A chemical is added. Nitrate ions can still bind to the membrane proteins involved in uptake, but the chemical prevents these proteins from changing shape.
Predict the effect of the chemical on nitrate ion uptake. 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.