Cambridge O Level Biology 5090: Transport in humans (5090) – Practice Questions

These are original questions written for Marlbridge, for revision and practice on this content. They are not reproduced past-paper questions, and they do not replicate the exam’s exact structure, question count or mark tariffs – examination boards hold copyright in their own papers. Use these alongside the official past papers from your board or school.

These questions cover Topic 11, Transport in humans, of the Cambridge O Level Biology 5090 syllabus for examination in 2026, 2027 and 2028: every learning outcome in sections 11.1 to 11.4, including the heart-rate investigation. The syllabus is not tiered, so every question applies to every candidate.

Revise first with the study guide and the revision notes. The course hub and the printable checklist list the other topics, and the free 10-minute diagnostics help you decide what to revise next. A calculator is useful for questions 5, 6 and 9.

Questions

1. Identify each structure of the heart from its description.

(a) The wall of muscle between the left and right sides. [1] (b) The type of valve between the left atrium and the left ventricle. [1] (c) Blood vessels on the outside of the heart that supply its muscle. [1] (d) The type of valve at the base of the pulmonary artery. [1]

2. Humans have a double circulation.

(a) Describe what is meant by a double circulation. [1] (b) Explain why it is an advantage to have a low pressure circulation to the lungs and a high pressure circulation to the body. [2]

3. Explain why:

(a) the wall of the left ventricle is thicker than the wall of the right ventricle [2] (b) the walls of the atria are thinner than the walls of the ventricles. [2]

4. Describe how the contraction of the heart muscle and the action of the valves move blood through the heart in one heartbeat, starting when the atria contract. [5]

5. A student measured his pulse for 30 s, three times at rest and three times straight after 2 minutes of skipping.

	Count 1	Count 2	Count 3
Beats in 30 s at rest	36	38	37
Beats in 30 s after skipping	62	64	63

(a) Calculate the mean resting heart rate in beats per minute. [2] (b) Calculate the percentage increase in heart rate after skipping. Give your answer to one decimal place. [2] (c) After skipping, his heart rate was 126, 104, 88, 74 and 74 beats per minute at 1, 2, 3, 4 and 5 minutes. State how long his heart rate took to return to the resting value. [1] (d) Explain why heart rate increases during physical activity. [3]

6. On an ECG trace, the peaks of successive heartbeats occur at 0.40 s, 1.15 s, 1.90 s, 2.65 s and 3.40 s.

(a) Calculate the heart rate in beats per minute. [2] (b) State two other ways of monitoring the activity of the heart. [2]

7. (a) Compare the structure of an artery with the structure of a vein. [3] (b) Explain how the structure of an artery is related to the pressure of the blood it carries. [2] (c) Explain how the wall of a capillary suits its function. [1]

8. Name the blood vessel that:

(a) carries blood from the lungs to the heart [1] (b) carries blood rich in absorbed amino acids from the small intestine to the liver [1] (c) carries blood from the aorta to a kidney [1] (d) carries blood from the liver towards the heart. [1]

9. A stained blood smear is viewed under a light microscope. Cell X has no nucleus. Cell Y has a lobed nucleus and much cytoplasm. Cell Z has a large, round nucleus that almost fills the cell.

(a) Identify cells X, Y and Z. [3] (b) State the function of cell Y and of cell Z. [2] (c) At ×2500, cell Y measures 30 mm on the image. Calculate its actual diameter in µm. [2]

10. (a) Describe the role of platelets when the skin is cut. [2] (b) Name four substances, other than proteins, transported in the plasma. [2] (c) Describe how glucose passes from the blood in a capillary to a muscle cell, and how carbon dioxide passes the other way. [4]

11. (a) Describe coronary heart disease and explain how it can damage the heart. [3] (b) Discuss the role of diet and exercise in reducing the risk of coronary heart disease. [4]

Answers

1. (a) Septum [1] (b) Atrioventricular valve [1] (c) Coronary arteries [1] (d) Semilunar valve [1] [4] Examiner insight: Use the syllabus term “atrioventricular” in (b); in (c), “coronary veins” or “aorta” names the wrong vessel and cannot be credited.

2. (a) Blood passes through the heart twice for each complete circuit of the body. [1] (b) Low pressure to the lungs avoids damaging the delicate lung capillaries. [1] High pressure delivers blood quickly to all the body tissues, supplying oxygen and glucose. [1] [3] Examiner insight: “Two circuits” alone is too vague for (a); the idea of passing through the heart twice per circuit is what earns the mark.

3. (a) The left ventricle pumps blood all round the body / over a longer distance [1], so it must produce a higher pressure, which needs more muscle; the right ventricle pumps only to the lungs. [1] (b) Atria pump blood only into the ventricles, a short distance, at low pressure [1]; ventricles pump blood out of the heart into the arteries, needing more force. [1] [4] Examiner insight: “Pumps more blood” is wrong, because both ventricles pump the same volume; the answer must be about pressure and distance.

4. Atria contract, pushing blood into the ventricles through the open atrioventricular valves. [1] Ventricles contract, raising pressure. [1] Atrioventricular valves close to prevent backflow into the atria. [1] Semilunar valves open, so blood is pushed into the aorta and pulmonary artery. [1] When the ventricles relax, the semilunar valves close, preventing backflow into the ventricles. [1] [5] Examiner insight: Sequence matters in a “describe” answer: each valve must be named and linked to the correct contraction, and “valves stop blood going backwards” without saying which valve and where is likely to earn little.

5. (a) Mean = (36 + 38 + 37) ÷ 3 = 37 beats per 30 s [1]; 37 × 2 = 74 beats per minute [1] (b) After skipping: mean 63 × 2 = 126 beats per minute; increase = 126 − 74 = 52 [1]; 52 ÷ 74 × 100 = 70.3% [1] (c) 4 minutes [1] (d) Muscles contract more, so they respire faster to release more energy. [1] They need more oxygen and glucose delivered. [1] More carbon dioxide must be removed, so the heart pumps blood faster. [1] [8] Examiner insight: An error carried forward from (a) into (b) is usually allowed, but the percentage must be calculated on the resting value, not the exercise value.

6. (a) Time per beat = 1.15 − 0.40 = 0.75 s [1]; heart rate = 60 ÷ 0.75 = 80 beats per minute [1] (b) Pulse rate [1]; listening to the sounds of the valves closing (with a stethoscope) [1] [4] Examiner insight: Use the interval between peaks, not the time of the first peak; 60 ÷ 0.40 gives 150, which scores nothing.

7. (a) Artery wall thicker than vein wall [1]; artery has more muscle and elastic tissue [1]; artery has a narrower lumen and no valves, vein a wider lumen with valves [1] (b) Blood is at high pressure, so a thick wall withstands it [1]; elastic tissue stretches and recoils with each surge, keeping blood flowing [1] (c) Wall one cell thick, giving a short diffusion distance for exchange [1] [6] Examiner insight: In a “compare” question each point needs both vessels, either stated or clearly implied with a comparative word such as “thicker”.

8. (a) Pulmonary vein [1] (b) Hepatic portal vein [1] (c) Renal artery [1] (d) Hepatic vein [1] [4] Examiner insight: Spelling that changes the vessel, such as “hepatic artery” for (d), cannot be credited; “vena cava” is wrong for (d) because the question asks for the vessel leaving the liver.

9. (a) X red blood cell [1]; Y phagocyte [1]; Z lymphocyte [1] (b) Y engulfs pathogens [1]; Z produces antibodies [1] (c) 30 mm = 30 000 µm [1]; 30 000 ÷ 2500 = 12 µm [1] [7] Examiner insight: “White blood cell” alone is not enough for Y or Z; the specific type is required, and the unit µm must be shown in (c).

10. (a) Platelets start clotting, in which soluble fibrinogen is converted to insoluble fibrin [1]; the clot prevents blood loss and the entry of pathogens [1] (b) Any four from: ions, glucose, amino acids, hormones, carbon dioxide, urea, vitamins (two correct [1], four correct [1]) (c) Plasma leaks out of the capillary to form tissue fluid around the cells [1]; glucose diffuses from the blood into the tissue fluid [1] and then into the muscle cell [1]; carbon dioxide diffuses from the cell into the tissue fluid and then into the blood [1] [8] Examiner insight: For (c), saying glucose goes “straight into the cell” misses the tissue fluid step, and “fibrinogen becomes fibrin” needs the soluble/insoluble change to be complete.

11. (a) A coronary artery becomes blocked (for example by fatty deposits) [1]; less blood reaches the heart muscle, so it gets too little oxygen and glucose [1]; the muscle cannot respire, so it cannot contract and may die (heart attack) [1] (b) Less saturated fat and cholesterol in the diet reduces fatty deposits in coronary arteries [1]; less salt helps keep blood pressure down [1]; regular exercise strengthens the heart muscle and helps control body mass, blood pressure and cholesterol [1]; but diet and exercise cannot change genetic predisposition, age or gender, so risk is reduced, not removed [1] [7] Examiner insight: A “discuss” answer that only lists risk factors scores little; each point needs a reason linked to the coronary arteries or heart, plus some balance.

Where marks are usually lost

• Writing “two circuits” for a double circulation without “passes through the heart twice”.
• Explaining the thicker left ventricle by volume pumped rather than pressure and distance.
• Naming “valves” without saying which ones open or close at each stage.
• Using the time of one ECG peak instead of the interval between peaks.
• Quoting a pulse count per 30 s as the heart rate.
• Calculating a percentage change on the wrong baseline.
• Mixing up the hepatic vein and the hepatic portal vein.
• Writing “white blood cell” when the question needs lymphocyte or phagocyte.
• Leaving out tissue fluid when describing exchange between blood and cells.

Next steps

• Recap with the revision notes.
• Re-read any weak area in the study guide.
• See every topic on the course hub and the printable checklist.
• Try all free 10-minute diagnostics.
• Book a free trial class.

Official syllabus

Cambridge O Level Biology 5090 syllabus for examination in 2026, 2027 and 2028 (version 4), Topic 11: Transport in humans, published by Cambridge Assessment International Education.