Science — AI-generated practice question

The lungs are designed in the following ways to maximise the surface area for gas exchange:

1. Alveoli: The lungs contain millions of tiny balloon-like structures called alveoli (singular: alveolus), which provide a very large surface area for the exchange of gases.
2. Rich blood supply: Each alveolus has an extremely thin wall and is surrounded by an extensive network of blood capillaries, allowing rapid diffusion of oxygen into the blood and carbon dioxide out.
3. Moist and thin walls: The alveolar walls are moist and one-cell thick, reducing the distance gases must diffuse.

Together, the millions of alveoli provide a total surface area of about 80 m², making gas exchange highly efficient.

Source: Chapter 5, Life Processes – Respiration section

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• The key concept examiners look for is alveoli — name them and explain their role.
• Three points are expected for 3 marks: (1) presence of alveoli, (2) large surface area created, (3) thin walls + rich capillary network for efficient diffusion.
• Avoid writing about the breathing mechanism; the question is specifically about structural design for maximising exchange area.
• Mentioning the approximate surface area (80 m²) is a bonus but not mandatory.