Cambridge IGCSE Biology 0610: Gas exchange in humans – 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, Gas exchange in humans (section 11.1), of the Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028. Unlabelled questions and parts use Core content (outcomes 11.1.1 to 11.1.5) and suit every candidate. Questions and parts marked (Extended) use Supplement content (outcomes 11.1.6 to 11.1.11), examined on Papers 2 and 4 only. A calculator is useful for the calculation parts.

Before you start, you may want the gas exchange study guide or the gas exchange revision notes. Course pages: Cambridge IGCSE Biology hub and Biology checklist. For a quick check across the whole course, try the Core diagnostic or the Extended diagnostic.

Questions

1. State three features of the gas exchange surface in humans that make gas exchange efficient. [3]

2. Name the structure in the human breathing system described in each statement.

(a) The tube that carries air from the larynx towards the lungs. [1] (b) The many small tubes that branch inside each lung. [1] (c) The sheet of muscle and tissue that separates the thorax from the abdomen. [1] (d) The tiny air sacs where gas exchange takes place. [1]

3. (Extended)

(a) State the function of the cartilage in the wall of the trachea. [1] (b) Name the intercostal muscles that contract when a person breathes in. [1]

4. A student sets up two boiling tubes, P and Q, each containing limewater. When she breathes in through the mouthpiece, room air bubbles through tube P. When she breathes out, her breath bubbles through tube Q. The limewater in tube Q turns milky after 25 seconds. The limewater in tube P has not changed after 3 minutes.

(a) State which tube contains the air she breathed out. [1] (b) State what the results show about the composition of expired air. [1] (c) State two variables the student should keep the same in tubes P and Q. [2]

5. A person’s inspired and expired air are analysed.

Gas	Inspired air / %	Expired air / %
Oxygen	21	17
Carbon dioxide	0.04	3.6

(a) Describe two differences between inspired and expired air shown in the table. [2] (b) Calculate the percentage decrease in oxygen from inspired to expired air. Give your answer to one decimal place. [2] (c) Calculate how many times greater the carbon dioxide percentage is in expired air. [1] (d) (Extended) Explain why expired air contains more carbon dioxide than inspired air. [2]

6. (Extended) Explain how the ribs, the intercostal muscles and the diaphragm cause air to enter the lungs. [5]

7. A student counts his breaths. At rest he takes 5 breaths in 20 seconds. Immediately after running for three minutes he takes 9 breaths in 15 seconds.

(a) Calculate his resting breathing rate in breaths per minute. [1] (b) Calculate his breathing rate after running, in breaths per minute. [1] (c) Calculate the percentage increase in breathing rate. [2] (d) Describe how the depth of his breathing changes after running. [1]

8. (Extended) Explain why the rate and depth of breathing increase during physical activity. [4]

9. (Extended) Explain how goblet cells and ciliated cells protect the breathing system from pathogens and particles. [4]

10. In one lung condition, the thin walls between neighbouring alveoli break down, so each lung contains fewer, larger air spaces.

(a) Explain how this condition affects gas exchange in the lungs. [3] (b) Suggest why a person with this condition becomes tired quickly when walking. [2] (c) (Extended) Suggest why this person’s breathing rate is higher than normal, even at rest. [2]

11. A spirometer is used to measure a woman’s breathing.

	Breaths per minute	Volume per breath / dm³
At rest	12	0.5
During exercise	30	2.0

(a) Calculate the volume of air she breathes in per minute at rest and during exercise. [2] (b) Calculate how many times greater the volume per minute is during exercise. [1] (c) (Extended) Describe what happens to the diaphragm, the ribs and the pressure in the thorax when she breathes out. [3] (d) (Extended) Explain why her expired air contains more water vapour than her inspired air. [2]

12. Plan an investigation into the effect of physical activity on the rate of breathing. [6]

Answers

1. Any three of: large surface area [1]; thin surface [1]; good blood supply [1]; good ventilation with air. Three separate features needed. Examiner insight: One mark goes to each separate feature from the syllabus list of four; a feature without a clear property (“good surface”) or one outside the list earns nothing.

2. (a) Trachea [1] (b) Bronchioles [1] (c) Diaphragm [1] (d) Alveoli [1] Examiner insight: Naming a neighbouring structure is marked wrong, so “bronchi” for (b) loses the mark; bronchi are the two large branches, bronchioles the many small ones.

3. (a) It keeps the trachea open / stops it collapsing [1] (b) The external intercostal muscles [1] Examiner insight: “Intercostal muscles” alone does not earn (b), because the question needs you to say which layer; “internal” is the wrong layer and is marked wrong, not ignored.

4. (a) Tube Q [1] (b) Expired air contains more carbon dioxide than inspired air [1] (c) Any two of: same volume of limewater [1]; same concentration of limewater [1]; same size of tube; same person breathing at a normal rate. Examiner insight: A comparison is needed for (b): “expired air contains carbon dioxide” is not enough, because inspired air contains some carbon dioxide too.

5. (a) Expired air contains less oxygen [1] and more carbon dioxide [1] (b) Decrease = 21 − 17 = 4; percentage decrease = 4 ÷ 21 × 100 [1] = 19.0% [1] (c) 3.6 ÷ 0.04 = 90 times [1] (d) Carbon dioxide is produced by respiration in cells [1]; it diffuses from the blood into the alveoli and is breathed out [1] Examiner insight: In (a), quoting the numbers without a comparative word (“less”, “more”) does not describe a difference; in (b) the working mark is usually still available if the final answer is misrounded, but the accuracy mark is not.

6. The external intercostal muscles contract (internal intercostals relax) [1]; the ribs move up and out [1]; the diaphragm contracts and flattens [1]; the volume of the thorax increases [1]; the pressure in the thorax decreases below atmospheric pressure, so air flows into the lungs [1]. Examiner insight: Volume and pressure are separate marking points, so “the chest gets bigger and air rushes in” earns only the volume mark; the pressure change must be stated in the correct direction.

7. (a) 5 × (60 ÷ 20) = 15 breaths per minute [1] (b) 9 × (60 ÷ 15) = 36 breaths per minute [1] (c) (36 − 15) ÷ 15 × 100 [1] = 140% [1] (d) Breathing becomes deeper (more air taken in per breath) [1] Examiner insight: Error carried forward is normally allowed in (c), so a wrong rate from (a) or (b) used correctly still earns the method mark; always show the subtraction and division.

8. Muscles contract more, so they carry out more aerobic respiration [1]; more carbon dioxide is produced, so its concentration in the blood increases [1]; this is detected by the brain [1]; which causes an increased rate and greater depth of breathing (to remove the carbon dioxide and supply more oxygen) [1]. Examiner insight: An answer built only on “the muscles need more oxygen” misses the carbon dioxide and brain marking points, which the syllabus names explicitly.

9. Goblet cells secrete mucus [1]; the mucus traps pathogens and particles [1]; ciliated cells have cilia that beat / waft [1]; which move the mucus up to the throat, away from the lungs [1]. Examiner insight: Each cell type needs its own action, so “cilia trap bacteria” gains nothing; the verb for cilia is move, beat or waft, and the verb for mucus is trap.

10. (a) The surface area for gas exchange is reduced [1]; so less oxygen diffuses into the blood [1] and less carbon dioxide diffuses out of the blood [1] (in a given time). (b) Less oxygen reaches the muscle cells [1]; so less aerobic respiration, and less energy is released [1] (c) Carbon dioxide concentration in the blood is higher [1]; this is detected by the brain, which increases the breathing rate [1] Examiner insight: “Suggest” questions reward applying a named syllabus idea to a new situation, so link the change to one of the four features (here surface area) rather than describing the disease in general terms.

11. (a) Rest: 12 × 0.5 = 6.0 dm³ per minute [1]; exercise: 30 × 2.0 = 60 dm³ per minute [1] (b) 60 ÷ 6.0 = 10 times [1] (c) The diaphragm relaxes and moves up into a dome [1]; the ribs move down and in [1]; the pressure in the thorax increases (above atmospheric), so air is forced out [1] (d) Water evaporates [1] from the moist lining of the alveoli into the air that is breathed out [1] Examiner insight: Units are required on calculated volumes, so “6 and 60” without dm³ per minute can lose the accuracy marks even though the arithmetic is right.

12. Any six of:

• Measure the resting breathing rate first, sitting still [1]
• Count breaths for a set time (for example one minute) and express as breaths per minute [1]
• Use different levels of activity (for example 1, 2 and 3 minutes of step-ups) as the variable changed [1]
• Count breaths immediately after each activity [1]
• Keep the same person and the same type and pace of exercise [1]
• Rest until the breathing rate returns to the resting value before the next trial [1]
• Repeat each activity level and calculate a mean Examiner insight: Planning marks are given for separate, specific points, so “do a fair test” earns nothing unless you name what is kept the same and how breathing rate is measured.

Where marks are usually lost

• Giving features of the alveoli without the reason (surface area, distance, gradient).
• Writing “bronchi” when the question describes bronchioles, or the reverse.
• Leaving out the pressure step in ventilation, or stating it the wrong way round.
• Saying the diaphragm moves up when breathing in.
• Describing a result of the limewater test without a comparison between the two tubes.
• Explaining faster breathing with “needs more oxygen” instead of carbon dioxide detected by the brain.
• Saying cilia trap dust or kill pathogens.
• Forgetting to convert breaths counted over 15 or 20 seconds into breaths per minute.
• Omitting units (breaths per minute, dm³ per minute, %) on calculated answers.
• Vague planning points such as “keep everything the same”.

Next steps

• Gas exchange revision notes
• Gas exchange study guide
• Respiration study guide, the next topic
• Cambridge IGCSE Biology hub
• Biology checklist
• 0610 Core diagnostic and 0610 Extended diagnostic
• Book a free trial class

Official syllabus

Cambridge IGCSE Biology 0610 syllabus for examination in 2026, 2027 and 2028, published by Cambridge Assessment International Education (Cambridge University Press & Assessment). Topic 11, Gas exchange in humans, section 11.1.