Mass transportAQA A-Level Biology: Topic test

20 questions, 54 marks

AQA A-Level Biology

Mass transport topic test

Total 54 marks

Name

Class

Date

1
A lugworm lives in a burrow in sand, where the concentration of oxygen in the water is low at low tide. Its haemoglobin has an oxyhaemoglobin dissociation curve that lies to the left of the curve for human haemoglobin.
(a)
What does it mean that the lugworm's curve lies to the left of the human curve?
[1 mark]
AIts haemoglobin has a lower affinity for oxygen than human haemoglobin.
BIts haemoglobin releases oxygen more readily than human haemoglobin at the same partial pressure of oxygen.
CIts haemoglobin has a higher affinity for oxygen and becomes saturated at a lower partial pressure of oxygen.
DIts haemoglobin does not show cooperative binding.
(b)
Which is an advantage of this haemoglobin for the lugworm?
[1 mark]
AIt can load oxygen at the low partial pressure of oxygen in the burrow.
BIt unloads all of its oxygen to the tissues at a high partial pressure of oxygen.
CIt is more saturated at the lungs than human haemoglobin.
DIt does not need to be inside red blood cells.
(c)
Explain why the oxyhaemoglobin dissociation curve is S-shaped rather than a straight line.
[2 marks]
Total for question 1: 4 marks
2
In a patient, the valve between the left atrium and the left ventricle does not close fully when the ventricle contracts, so some blood flows back into the atrium.
(a)
Which valve is faulty?
[1 mark]
AThe semilunar valve at the base of the aorta.
BThe valve between the right atrium and the right ventricle.
CThe semilunar valve at the base of the pulmonary artery.
DThe left atrioventricular (bicuspid) valve.
(b)
What is the effect of the fault during ventricular contraction?
[1 mark]
AMore blood than normal enters the aorta.
BSome blood returns to the left atrium, so less blood enters the aorta.
CBlood flows from the aorta back into the left ventricle.
DBlood flows from the right ventricle into the left ventricle.
(c)
The volume of blood leaving the patient's left ventricle each beat is 55 cm³ and her heart rate is 80 beats per minute. Calculate her cardiac output in dm³ per minute.
[2 marks]
Total for question 2: 4 marks
3
A child with severe protein deficiency has a swollen abdomen caused by the accumulation of tissue fluid. A blood test shows that the concentration of proteins in her blood plasma is very low.
(a)
Describe how tissue fluid is normally formed from blood plasma.
[3 marks]
(b)
Explain why her abdomen is swollen.
[4 marks]
Total for question 3: 7 marks
4
During a drought, trees in a woodland lose water from their leaves faster than their roots can absorb it. Scientists who fixed microphones to the trunks detected clicking sounds, which were caused by air bubbles forming in xylem vessels. The trees' leaves also produced less sucrose than usual.
(a)
Explain how water normally moves from the roots to the leaves in the xylem, and why an air bubble in a xylem vessel stops water moving through that vessel.
[6 marks]
(b)
Describe the mass flow hypothesis for the movement of sucrose from the leaves to the roots, and use it to suggest why translocation is slower during a drought.
[6 marks]
Total for question 4: 12 marks
5
Arterioles carry blood from arteries to capillary beds, and veins carry blood from capillary beds back to the heart. The wall of an arteriole contains a layer of smooth muscle, and veins contain valves.
(a)
What happens to the flow of blood to a capillary bed when the smooth muscle in the wall of its arteriole contracts?
[1 mark]
AIt increases, because the lumen of the arteriole widens.
BIt decreases, because the lumen of the arteriole narrows.
CIt is unchanged, because the pressure in the artery stays the same.
DIt increases, because the arteriole wall becomes thinner.
(b)
What is the function of the valves in veins?
[1 mark]
ATo increase the pressure of the blood.
BTo allow blood to flow in both directions.
CTo prevent the backflow of blood, so it flows in one direction towards the heart.
DTo control the amount of blood entering each capillary.
(c)
Suggest why the blood pressure in veins is much lower than in arteries.
[2 marks]
Total for question 5: 4 marks
6
A student supplied one leaf of a potted plant with carbon dioxide containing radioactive carbon-14 (¹⁴CO₂) in a sealed chamber in the light. After 24 hours, she cut the stem and roots into sections and tested each for radioactivity.
(a)
Why was ¹⁴CO₂ used?
[1 mark]
AThe ¹⁴C was incorporated into sugars made by photosynthesis, which are then transported and can be detected.
BThe ¹⁴C is absorbed by the roots and travels in the xylem.
CThe ¹⁴C blocks the stomata so that water cannot escape.
DThe ¹⁴C makes the plant photosynthesise more quickly.
(b)
Radioactivity was found in the roots after 24 hours. What does this show?
[1 mark]
AWater moves from the leaves to the roots in the xylem.
BThe roots absorbed ¹⁴CO₂ from the soil.
CThe radioactive carbon moved from the leaf to the root by diffusion only.
DOrganic substances made in the leaf are transported to the roots.
(c)
Explain why the radioactivity would be found in the phloem but not in the xylem.
[2 marks]
Total for question 6: 4 marks
7
A healthy person at rest has a cardiac output of 5.0 dm³ min⁻¹ and 150 g of haemoglobin per dm³ of blood. 1 g of haemoglobin can combine with 1.34 cm³ of oxygen. The blood leaving the lungs is 98% saturated with oxygen, and the blood returning from the tissues at rest is 75% saturated.
(a)
Calculate the volume of oxygen released to the tissues from each dm³ of blood.
[3 marks]
(b)
A patient with anaemia has only 90 g of haemoglobin per dm³ of blood, with the same saturations. Calculate the cardiac output she would need to release the same total volume of oxygen per minute as the healthy person, and state what this means for her heart.
[4 marks]
Total for question 7: 7 marks
8
A study followed 3000 adults aged 40 to 60 for ten years. Of 1200 adults with normal blood pressure, 36 had a heart attack. Of 1800 adults with raised blood pressure, 126 had a heart attack. A larger proportion of the adults with raised blood pressure were smokers.
(a)
Evaluate whether the data show that raised blood pressure causes heart attacks.
[6 marks]
(b)
Explain how a blockage in a coronary artery leads to a heart attack.
[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).