Describe and explain the features of a gas exchange surface.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2017). The mark or mark type is shown in brackets.

1. [4] 1 thin / one cell thick / short distance ;
2. [4] 2 moist;
3. [4] 3 large surface area;
4. [4] 4 permeable;
5. [4] 5 maximum / more / quick / efficient + diffusion / absorption / exchange;
6. [4] 6 reference to dissolving / in solution ;
7. [4] 1 faster / deeper + breathing;
8. [4] 2 more + oxygen ;
9. [4] 3 (oxygen) in lungs / inhaled / in blood ;
10. [4] 4 muscle;
11. [4] 5 faster/increased + respiration / oxidation of glucose ;
12. [4] 6 aerobic;
13. [4] 7 more energy + required / released ;
14. [4] 8 more + carbon dioxide removed AW ;
15. [4] 9 delays / prevents AW + anaerobic respiration;
16. [2] 1 less oxygen in atmosphere (at high altitude) ;
17. [2] 2 more + haemoglobin ;
18. [2] 3 oxyhaemoglobin OR more + oxygen carried / supplied ;
19. [2] 4 competitive advantage AW;