Biology 9700 · AS & A Level · The gas exchange system
The gas exchange system — practice question
The human gas exchange system enables oxygen to be taken up efficiently into the blood and carbon dioxide to be removed by excretion.
Each tissue in the human gas exchange system is adapted to carry out its own function.
(a(i))[2]
Squamous epithelial cells lack cilia, whereas ciliated epithelial cells have them.
Suggest why ciliated epithelial cells are unsuitable as the lining tissue of the alveolar walls.
(a(ii))[2]
Goblet cells and mucous glands help to keep the gas exchange system healthy by making mucus that traps pathogens and other particles, including dust.
Explain why ciliated epithelial cells are also important in maintaining the health of the gas exchange system.
(b)[4]
Suggest explanations for the differences shown in Fig. 5.1.
Worked solution & mark scheme
This 8-mark question has a full step-by-step worked solution and mark scheme. One marking point: “A thicker epithelium lengthens the diffusion pathway for $\mathrm{O_2}$ and $\mathrm{CO_2}$” …