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IGCSEBiology
Trial Class

Original practice · 5 questions · 15 marks · about 17 minutes

Gas Exchange Surfaces Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your understanding of how gas exchange surfaces are adapted for efficient exchange of oxygen and carbon dioxide.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 4 Both 4 marks Difficulty 3/5

    Describe four features of an efficient gas exchange surface.

    Show model answer and marking guidance
    1. Large surface area: more space for gas molecules to diffuse across.
    2. Thin walls (one cell thick): short diffusion distance.
    3. Good blood supply: maintains a steep concentration gradient.
    4. Moist surface: gases dissolve before diffusing across the membrane.

  2. Question 2

    Paper 4 Extended 3 marks Difficulty 3/5

    Explain how the structure of an alveolus is adapted for efficient gas exchange.

    Show model answer and marking guidance
    1. Spherical shape and millions of alveoli provide a very large total surface area.
    2. Alveolar wall is one cell thick: short diffusion distance for O₂ and CO₂.
    3. Dense network of capillaries around each alveolus: blood flows close to the air, maintaining concentration gradients.

  3. Question 3

    Paper 4 Both 3 marks Difficulty 3/5

    Explain why a concentration gradient is important for gas exchange in the lungs.

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    1. Oxygen concentration is higher in the alveolar air than in the blood: O₂ diffuses into the blood.
    2. CO₂ concentration is higher in the blood than in the alveolar air: CO₂ diffuses into the alveolus.
    3. Without a concentration gradient, net diffusion would not occur.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 1/5

    Name the gas exchange surface in the lungs.

    Show model answer and marking guidance
    1. Alveoli (air sacs).
    2. Oxygen diffuses into the blood and carbon dioxide diffuses out.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 4/5

    Fish use gills for gas exchange. State three features of gills that make them efficient gas exchange surfaces.

    Show model answer and marking guidance
    1. Gill filaments have many lamellae: providing a large surface area.
    2. Lamellae are thin: short diffusion distance.
    3. Counter-current flow: blood and water flow in opposite directions, maintaining a concentration gradient along the entire length.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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