Molecules, Transport and HealthEdexcel International A Level Biology: Topic test

1. 1
   Bees make honey from nectar, which is rich in the disaccharide sucrose. An enzyme in the bee's saliva, invertase, hydrolyses the sucrose in the nectar into monosaccharides.

   (a)

   Which pair of monosaccharides is released when sucrose is hydrolysed?

   [1 mark]

   • AGlucose and galactose
   • BGlucose and glucose
   • CGlucose and fructose
   • DFructose and galactose

   (b)

   Which statement correctly describes the hydrolysis of sucrose?

   [1 mark]

   • AA molecule of water is used to break a glycosidic bond
   • BA molecule of water is released as a glycosidic bond forms
   • CA molecule of water is used to form an ester bond
   • DA molecule of water is released as a glycosidic bond is broken

   (c)

   Describe how a molecule of sucrose is formed from its monosaccharides.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Varicose veins develop when the valves in the veins of the legs stop working properly. Blood then pools in the veins, which become swollen and twisted.

   (a)

   What is the normal function of the valves in a vein?

   [1 mark]

   • ATo pump blood towards the heart by contracting
   • BTo allow exchange of substances with the tissue fluid
   • CTo maintain a high blood pressure in the vein
   • DTo prevent the backflow of blood

   (b)

   Compared with an artery, which feature is found in a vein?

   [1 mark]

   • AA thick wall containing much elastic tissue
   • BA relatively wide lumen and a thin wall
   • CA narrow lumen to maintain pressure
   • DA wall made of a single layer of cells

   (c)

   Explain how blood is returned to the heart through the veins of the leg, even though the blood pressure in them is low.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Llamas live in the Andes at altitudes of up to 4,000 m, where the partial pressure of oxygen in the air is about 60% of that at sea level. The oxygen dissociation curve for llama haemoglobin lies to the left of the curve for human haemoglobin.

   (a)

   Explain the advantage to llamas of having haemoglobin with this dissociation curve.

   [3 marks]

   (b)

   During a hard climb, the muscle cells of a llama release more carbon dioxide. Explain how this increases the supply of oxygen to the muscle cells.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A 52-year-old taxi driver smokes 20 cigarettes a day, eats a diet high in saturated fat and has a blood pressure of 160/100 mmHg. His blood LDL cholesterol concentration is well above the recommended level. A coronary angiogram shows that one of his coronary arteries is almost blocked.

   (a)

   Describe how atherosclerosis develops and how it can lead to a heart attack.

   [6 marks]

   (b)

   Explain how the man's lifestyle has increased his risk of cardiovascular disease and how the risk could be reduced by changes in lifestyle and by drug treatment.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   In a healthy human heart, the pressure in the left ventricle rises to about 16 kPa during ventricular systole, whereas the pressure in the right ventricle rises to only about 4 kPa.

   (a)

   Which row describes the valves of the heart during ventricular systole?

   [1 mark]

   • AAtrioventricular valves closed and semilunar valves open
   • BAtrioventricular valves open and semilunar valves closed
   • CAtrioventricular valves open and semilunar valves open
   • DAtrioventricular valves closed and semilunar valves closed

   (b)

   Which blood vessel carries oxygenated blood into the left atrium?

   [1 mark]

   • AAorta
   • BVena cava
   • CPulmonary artery
   • DPulmonary vein

   (c)

   Explain why the pressure in the left ventricle is higher than that in the right ventricle.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A brown bear stores energy for winter hibernation as triglycerides in adipose tissue. Each triglyceride molecule contains one molecule of glycerol joined to three fatty acids.

   (a)

   How many molecules of water are released when one molecule of triglyceride is formed from glycerol and fatty acids?

   [1 mark]

   • A1
   • B3
   • C4
   • D6

   (b)

   Which type of bond joins a fatty acid to glycerol in a triglyceride?

   [1 mark]

   • AGlycosidic
   • BPeptide
   • CEster
   • DHydrogen

   (c)

   Distinguish between a saturated fatty acid and an unsaturated fatty acid.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A cohort study followed 8,000 women aged 40 to 50 for 15 years. At the start, 2,000 of the women were smokers and 6,000 were non-smokers. During the study, 160 of the smokers and 120 of the non-smokers had a heart attack.

   (a)

   Calculate the percentage of each group that had a heart attack and the number of times more likely a smoker was to have a heart attack than a non-smoker.

   [3 marks]

   (b)

   The researchers concluded that smoking causes heart attacks. Evaluate how far the data support this conclusion.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   An African elephant is a large mammal with a small surface area to volume ratio, and many of its cells lie deep inside its body. Its heart pumps blood through a closed circulatory system of arteries, capillaries and veins.

   (a)

   Describe how the structures of arteries, capillaries and veins are related to their functions.

   [6 marks]

   (b)

   Explain how the heart and haemoglobin together ensure that oxygen is supplied to the respiring cells of the elephant.

   [6 marks]

   Total for question 8: 12 marks

End of questions