2 marksFig. 1 shows the process of active transport.
Fig. 1
State two differences between active transport and diffusion.
1 markMolecule X in Fig. 1 enters the cell by active transport.
Give one example of molecule X.
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10 marksTable 1 shows some of their measurements.
Table 1
| closed stomata | open stomata | |
| ion concentration in guard cells /pmol | 0.3 | 2.5 |
| guard cell volume/μm3 | 4000.0 | 6500.0 |
| turgor pressure in the guard cells /MPa | 2.0 | 4.8 |
| width of stomatal opening/μm | 0.0 | 8.0 |
Ions move into guard cells by active transport.
Describe how the ions move into the guard cells.
[2]
Describe and explain how the change in ion concentration causes the guard cell volume to change.
Use the information in Table 1 in your answer.
(iii)
The botanists left the broad bean plants unattended for three days. During this time the broad bean plants wilted.
Suggest two environmental factors that can cause plants to wilt.
[2]
2 marksTable 2 shows the concentrations of four mineral ions in the roots of a plant and in the surrounding soil.
These minerals are all essential to the health of the plant.
Table 2
| mineral ion | concentration in millimoles per gram | |
| plant root | soil | |
| calcium | 0.15 | 0.03 |
| magnesium | 0.06 | 0.02 |
| nitrate | 0.68 | 0.53 |
| potassium | 0.26 | 0.01 |
Based on the information in Table 2, explain why the plant roots cannot absorb these mineral ions by diffusion.
2 marksCalcium ions play a structural role in cell walls and membranes of the plant cell.
Calculate the percentage difference between the concentration of calcium ions inside and outside the plant root, using the data from Table 1.
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3 marksA group of scientists investigated the rates of absorption of different sugars using two pieces of the intestine.
One of these pieces were treated with cyanide, which is a toxin that prevents cellular respiration from occurring.
The results of the investigation are shown in Table 1.
Table 1
|
sugar |
absorption rate / arbitrary units | |
| healthy intestine | intestine treated with cyanide | |
| A | 121 | 62 |
| B | 47 | 45 |
| C | 68 | 67 |
| D | 89 | 35 |
Suggest the method by which sugar A, B and C are absorbed by the intestine.
3 marksThe scientists concluded that sugar D is absorbed by active transport.
Explain how they came to this conclusion by using evidence from Table 1.
2 marksOne of the scientists states that 'All four of the sugars investigated could be absorbed by diffusion'.
Determine whether this statement is correct by using the information in Table 1 and your knowledge of diffusion.
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The diagram shows a root hair cell from a lemon tree and some soil particles.
The lemon tree has grown in the same soil for many years so the soil now lacks magnesium.
Describe and explain the effect on the lemon tree of a lack of magnesium.
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