CAIE A-Level Biology AS 9.1.7 Gas Exchange Between Alveolar Air and Blood Questions
Explain alveolar gas exchange and diffusion factors using evidence from each question and mark scheme.
- Syllabus
- 2028–2030
- Course
- Biology 9700
- Level
- AS
Exam points
- Explain gas exchange between alveolar air and blood and the factors affecting diffusion.
CAIE A-Level Biology AS 9.1.7 Gas Exchange Between Alveolar Air and Blood Questions question 1
[Maximum number: 2]
In a double circulatory system, blood passes through the heart twice in one complete circuit of the body. The complete circuit consists of the pulmonary circulation and the systemic circulation.
The alveolus is the gas exchange surface in mammals. For efficient oxygen uptake, a steep diffusion gradient is maintained between the alveolar air and the blood.
Suggest how the steep diffusion gradient for oxygen is maintained at the gas exchange surface.
any two from:
ventilation / breathing (movements) / inspiration / inhalation, brings in oxygen ;
blood flow (in pulmonary capillaries) removes oxygen ;
oxygen binding to haemoglobin / oxyhaemoglobin formation, (removes oxygen) ;
deoxygenated blood arriving / blood arriving low in oxygen ;
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