O Level / IGCSE Biology chapter 11: Transport in humans MCQs with answers
By Team Megalecture · Updated 4 Nov 2026
43 exam-style questions on Transport in humans, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.
Try each one, then open the answer. These ten stay the same; the test draws new ones every time.
1. Which blood vessel carries oxygenated blood from the lungs to the heart?
A
pulmonary vein
B
pulmonary artery
C
aorta
D
vena cava
Show answer
Answer: A. The pulmonary vein is the only vein carrying oxygenated blood. The pulmonary artery carries deoxygenated blood to the lungs.
2. A fish has a single circulation: blood passes from the heart to the gills and then straight on to the body. What is a disadvantage compared with a double circulation?
A
blood passes through the heart twice, so the heart has to work harder
B
the heart has no valves, so blood flows back into the gills
C
blood reaches the body tissues at a lower pressure, so delivery is slower
D
a mixture of oxygenated and deoxygenated blood reaches the body tissues
Show answer
Answer: C. Pressure is lost in the gill capillaries, so blood travels to the body slowly. In mammals the heart re-pressurises blood after the lungs.
3. Why are the walls of capillaries only one cell thick?
A
so substances can diffuse quickly between the blood and the cells
B
so that valves can fit inside them and prevent backflow of blood
C
so that blood can be carried quickly back to the heart
D
so that they can withstand the high pressure of blood from the arteries
Show answer
Answer: A. Capillaries are where substances pass between blood and cells, so thin walls speed up diffusion.
4. What is the advantage of a double circulation?
A
the heart does less work because it has to pump blood only once per circuit
B
oxygenated and deoxygenated blood are mixed to give an average oxygen level
C
blood can reach the body at a higher pressure than it reaches the lungs
D
the pressure of the blood is kept the same in every part of the system
Show answer
Answer: C. A separate pump for each circuit keeps pressure low in the delicate lungs and high for fast delivery to the body.
5. A person with anaemia has fewer red blood cells than normal. Which symptom is most likely?
A
tiredness, because less oxygen reaches the muscles
B
slow clotting of blood after a cut
C
frequent infections, because fewer antibodies are made
D
a very high blood glucose concentration
Show answer
Answer: A. Red blood cells contain haemoglobin, which carries oxygen. With fewer red cells, less oxygen is delivered to the muscles for respiration, so the person feels tired. Clotting depends on platelets and antibodies on lymphocytes.
6. Which blood vessels have valves along their length?
A
arteries
B
the aorta and pulmonary artery
C
capillaries
D
veins
Show answer
Answer: D. Veins carry blood at low pressure; their valves stop blood flowing backwards.
7. Four adults are described. Which one has the highest risk of coronary heart disease?
A
a non-smoker who runs daily and eats a diet low in saturated fat
B
a smoker who runs daily and eats a diet low in saturated fat
C
a smoker who takes no exercise and eats a diet high in saturated fat
D
a non-smoker who walks daily and eats a diet rich in fibre
Show answer
Answer: C. Smoking, lack of exercise and a diet high in saturated fat are all risk factors; this person has all three. Each of the others has at most one.
8. After a meal rich in carbohydrate, which vessel contains blood with the highest concentration of glucose?
A
aorta
B
hepatic portal vein
C
hepatic vein
D
renal vein
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Answer: B. Glucose absorbed in the small intestine travels to the liver in the hepatic portal vein. The liver stores some as glycogen, so blood leaving in the hepatic vein and travelling in the aorta has a lower concentration.
9. Which substance is carried mainly dissolved in the plasma rather than by red blood cells?
A
oxygen
B
haemoglobin
C
glucose
D
fibrin
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Answer: C. Glucose, amino acids, ions, urea, hormones and carbon dioxide travel in plasma. Oxygen is carried by haemoglobin inside red cells.
10. Why must the blood pressure in the circulation to the lungs be lower than in the circulation to the body?
A
high pressure would force too much oxygen into the blood
B
the lungs need a smaller volume of blood than the body tissues do
C
the lungs are further from the heart than any other organ
D
high pressure would damage the thin walls of the lung capillaries
Show answer
Answer: D. Lung capillaries are very thin to allow fast diffusion; high pressure would damage them.
43, each with the answer and a short explanation, across 4 topics: Circulatory system, Heart, Blood vessels, Blood. Every chapter test draws ten of them, so you can take it many times.
Is the O Level / IGCSE Biology chapter 11 test free?
Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.
How is the chapter test marked?
The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.
