Question
SLPaper 2
The diagram shows the structure of an alveolus and an adjacent capillary.
1.[2]
Outline the functions of type I and type II pneumocytes.
Verified
Solution
Type I:
- Carry out gas exchange
OR
Diffusion of gases//;1 mark
Type II:
- Secrete fluid/surfactant;
1 mark
2.[3]
Explain how gases are exchanged between the air in the alveolus and the blood in the capillaries.
Verified
Solution
- concentration in alveolar air greater than in capillary/blood «prior to gas exchange»
OR
Hemoglobin in blood binds oxygen maintaining the concentration gradient;1 mark - gas dissolves in water lining the alveolus;
1 mark - diffuses through wall of alveolus and capillary into blood;
1 mark - concentration in blood greater than in alveolar air «prior to gas exchange»;
1 mark - diffuses through wall of capillary and alveolus into alveolar airspace;
1 mark