Name and describe each process that must take place in order to remove molecules of carbon dioxide from the blood of a person to the air in the atmosphere.

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

1. [7] diffusion;
2. [7] down concentration gradient / from high to low concentration;
3. [7] plasma / hydrogencarbonate / HCO3¯;
4. [7] capillary;
5. [7] dissolves + mucus / moist lining / water film ;
6. [7] alveoli / air sac;
7. [7] exhalation / expiration / breathed out ;
8. [7] intercostal muscles relax OR internal intercostal muscles contract ;
9. [7] ribs + down / in / fall;
10. [7] diaphragm + relaxes / moves up / becomes domed ;
11. [7] decreased volume / increased pressure ;
12. [7] (out through) bronchioles / bronchi / bronchus / trachea;
13. [3] photosynthesis ;
14. [3] reacts with + water ;
15. [3] light + energy;
16. [3] produce AW + glucose / starch / carbohydrate / sugar ;
17. [3] chlorophyll / chloroplasts;