O-LevelBiologyRespiration5090/21 · May/June 2017 · Q610 Marks
Section B Answer both questions in this section. 6
- (a)Describe the role of the cilia in the trachea.[3]
- (b)Fig. 6.1 shows components of the human gas exchange surface and an associated blood vessel. State the characteristics, and describe the roles, of each of the components shown in Fig. 6.1. You should make reference to named structures in your answer.[7]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (May/June 2017). The mark or mark type is shown in brackets.
- [3] 6(a) move mucus ; (containing) bacteria / pathogens / dust ; (moves) up / away from lungs AW ; prevent infection;
- [7] 6(b) reference to diffusion ; (for) O2/CO2 + exchange AW ; alveolus / air sac; large surface area; one cell thick + wall ; moist AW/mucus ; (gases) to dissolve ; capillary; one cell thick + wall ; connect AW arteries + veins ; blood + moving; red blood cells / erythrocytes ; no nucleus; biconcave; contain haemoglobin ; live for 90/120 days OR 3/4 months; carry oxygen; plasma; carriage of carbon dioxide;
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