Surface area, gas exchange and digestionAQA A-Level Biology: Topic test

20 questions, 54 marks

AQA A-Level Biology

Surface area, gas exchange and digestion topic test

Total 54 marks

Name

Class

Date

1
A flatworm has no specialised gas exchange system. A student models its body as a cuboid 10 mm long, 4 mm wide and 1 mm thick.
(a)
What is the surface area to volume ratio of the model flatworm?
[1 mark]
A1.35 : 1
B2.7 : 1
C5.4 : 1
D0.37 : 1
(b)
Why can the flatworm exchange gases by diffusion across its body surface alone?
[1 mark]
AIt has a small surface area to volume ratio.
BIt has a thick, waterproof body covering.
CIt has a high metabolic rate that needs a large oxygen supply.
DIts large surface area to volume ratio and thin body mean that oxygen reaches all of its cells quickly by diffusion.
(c)
A second flatworm has the same shape but every dimension is twice as large. Calculate its surface area to volume ratio.
[2 marks]
Total for question 1: 4 marks
2
A desert beetle spends much of the day with its spiracles closed, opening them only briefly. Its tracheal system carries air to all of its tissues.
(a)
Which sequence shows the path taken by oxygen into the beetle's cells?
[1 mark]
ASpiracles, tracheae, tracheoles, body cells.
BTracheae, spiracles, tracheoles, body cells.
CSpiracles, tracheoles, tracheae, body cells.
DTracheoles, tracheae, spiracles, body cells.
(b)
Why is closing the spiracles described as a compromise?
[1 mark]
AIt increases water loss but increases oxygen uptake.
BIt prevents any carbon dioxide from being produced.
CIt reduces water loss by evaporation but also reduces the exchange of gases.
DIt increases the surface area for gas exchange but reduces the diffusion distance.
(c)
Explain how the structure of the tracheoles makes gas exchange with the beetle's muscle cells rapid.
[2 marks]
Total for question 2: 4 marks
3
A runner's breathing was measured at rest and during exercise. At rest, her tidal volume was 0.50 dm³ and her breathing rate was 14 breaths per minute. During exercise, her tidal volume rose to 2.2 dm³ and her pulmonary ventilation rate was 52.8 dm³ min⁻¹.
(a)
Calculate her pulmonary ventilation rate at rest, her breathing rate during exercise, and the percentage increase in her pulmonary ventilation rate during exercise.
[3 marks]
(b)
Describe how the diaphragm and the intercostal muscles cause air to be taken in and forced out of her lungs during exercise.
[4 marks]
Total for question 3: 7 marks
4
A man has a condition in which the cells lining his ileum produce very little of the membrane-bound enzyme lactase. After drinking milk, which contains the disaccharide lactose, he suffers abdominal pain, gas and watery diarrhoea.
(a)
Explain these symptoms.
[6 marks]
(b)
In a person with normal lactase production, the glucose and galactose formed from lactose are absorbed rapidly. Explain how the structure of the ileum wall and the mechanism of absorption allow this.
[6 marks]
Total for question 4: 12 marks
5
In a dicotyledonous leaf, carbon dioxide diffuses from the air into the cells of the mesophyll through stomata. Each stoma is opened and closed by a pair of guard cells.
(a)
Which sequence shows the route taken by carbon dioxide into a mesophyll cell?
[1 mark]
AStoma, air spaces in the mesophyll, cell wall, cell.
BCell wall, stoma, air spaces in the mesophyll, cell.
CAir spaces in the mesophyll, stoma, cell wall, cell.
DStoma, cell wall, air spaces in the mesophyll, cell.
(b)
Why is the closing of stomata in hot, dry conditions a compromise?
[1 mark]
AIt increases the surface area for gas exchange but reduces the number of stomata.
BIt reduces carbon dioxide production but increases oxygen uptake.
CIt increases water loss but increases carbon dioxide uptake.
DIt reduces water loss by evaporation but also reduces the carbon dioxide entering the leaf.
(c)
Explain how the structure of the leaf is adapted for rapid gas exchange.
[2 marks]
Total for question 5: 4 marks
6
In emphysema, the walls between neighbouring alveoli break down, so the lungs contain fewer, larger air spaces. The alveolar walls also lose their elasticity.
(a)
Why does gas exchange become less efficient in a person with emphysema?
[1 mark]
AThe concentration of oxygen in the air in the alveoli increases.
BThe surface area of the gas exchange surface is reduced.
CThe diffusion distance between the air and the blood is increased because the alveolar walls become thicker.
DThe number of capillaries around each alveolus increases.
(b)
The loss of elasticity affects breathing. Which effect is expected?
[1 mark]
AThe tidal volume is greater than normal.
BInhalation becomes impossible.
CExhalation is less complete because the lungs recoil less.
DThe diaphragm can no longer contract.
(c)
Explain why a person with emphysema becomes breathless more easily during exercise.
[2 marks]
Total for question 6: 4 marks
7
Cell L is a spherical single-celled organism of diameter 2 μm. Cell M is a larger spherical single-celled organism of diameter 20 μm. Both exchange oxygen with the surrounding water across their surfaces.
(a)
For a sphere, surface area = 4πr² and volume = (4/3)πr³. Calculate the surface area to volume ratio for each cell and compare them.
[3 marks]
(b)
Use your answer to explain why large multicellular organisms need specialised gas exchange systems.
[4 marks]
Total for question 7: 7 marks
8
A study compared the incidence of a lung disease in children living within 100 m of a busy road with that in children living more than 5 km from any major road. Of 2000 children living near the road, 280 had the disease. Of 2000 children living far from major roads, 120 had the disease. The groups were similar in age and sex, but more families living near the road lived in rented flats.
(a)
Evaluate whether these data show that traffic pollution causes lung disease.
[6 marks]
(b)
Describe how the structure of the human gas exchange system allows oxygen to reach the blood efficiently.
[6 marks]
Total for question 8: 12 marks

End of questions

Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).