B3.1 Gas Exchange

Question 1

Define Gas Exchange

Answer 1

The exchange of oxygen and carbon dioxide between the alveoli and bloodstream (via passive diffusion) across a membrane.

Question 2

Role of diffusion in gas exchange

Answer 2

Moves oxygen out of alveoli and into blood. Moves carbon dioxide in blood of capillaries into alveoli, to be expelled by lungs.

Question 3

Function of Permeability property of gas exchange surfaces

Answer 3

Cell membrane allowing substances such as oxygen and carbon dioxide to pass through it.

Membrane must be permeable to the gases required in gas exchange to be able to allow gas exchange to occur.

Question 4

Function of Large SA:V ratio for gas exchange

Answer 4

With higher SA:V ratio, there is large enough respiratory surface for diffusion to take place, per volume of air or water taken in by ventilation.

Question 5

Function of Moistness in gas exchange

Answer 5

For gas exchange to happen, oxygen and carbon dioxide must first dissolve in water or a solution before they can diffuse across a cell. So specialized respiratory surface must be moist.

Question 6

Function of being “thin” for gas exchange

Answer 6

Respiratory surface must be as thin as possible to make distance molecules travel as short as possible. Short diffusion distance = diffuse faster.

Question 7

Function of Large Concentration gradient as a property for gas exchange

Answer 7

Larger concentration gradient, higher the rate of diffusion.

Question 8

Why must concentration gradients be maintained at exchange surfaces?