Active Transport (Cambridge O Level Biology)

Exam Questions

33 mins5 questions
1a
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2 marks

Fig. 1 shows the process of active transport.

active transport

Fig. 1

State two differences between active transport and diffusion.

1b
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1 mark

Molecule X in Fig. 1 enters the cell by active transport.

Give one example of molecule X.

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1a
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10 marks
More than 40 years ago, botanists studied the leaves of broad bean plants and discovered that guard cells control the opening and closing of stomata. They found that stomata were open when the guard cells were turgid.

Table 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

(i)

Ions move into guard cells by active transport.

Describe how the ions move into the guard cells.

[2]

(ii)

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.

[6]

(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]

1b
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2 marks

Table 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.

1c
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2 marks

Calcium 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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2a
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3 marks

A 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.

2b
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3 marks

The scientists concluded that sugar D is absorbed by active transport.

Explain how they came to this conclusion by using evidence from Table 1.

2c
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2 marks

One 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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3a5 marks

The diagram shows a root hair cell from a lemon tree and some soil particles.

q3a-3-2-active-immunity-medium-sq-cie-o-level-biology

(i)
State one feature, visible in the diagram, which shows that a root hair cell is a plant cell.
[1]

(ii)
Describe how mineral ions pass from the soil into the root hair cell.
[4]
3b2 marks

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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