gas exchange exam qs

Question 1

Explain how the counter current mechanism in fish gills ensures the maximum amount of
the oxygen passes into the blood flowing through the gills

Answer 1

Water and blood flow in opposite directions;
Allow diagram showing counter-flow
2. Blood always passing water with a higher oxygen concentration;
3. Diffusion gradient maintained throughout length

Question 2

Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide
between the blood and the alveoli.

Answer 2

Less carbon dioxide exhaled
2. (So) reduced concentration gradient (between blood and alveoli);
More carbon dioxide stays in blood;

Question 3

(a) Describe the pathway taken by an oxygen molecule from an alveolus to the blood.

Answer 3

(Across) alveolar epithelium;
2. Endothelium