What will increase the rate of diffusion across a gas exchange surface?
A) a decrease in the concentration gradient
B) a decrease in the diffusion distance
C) a decrease in the kinetic energy of molecules
D) a decrease in the surface area of the gas exchange surface
▶️ Answer/Explanation
Ans: B
The rate of diffusion is given by Fick’s Law: \( \text{Rate} \propto \frac{\text{Surface Area} \times \text{Concentration Gradient}}{\text{Diffusion Distance}} \).
A decrease in diffusion distance (B) increases the rate, while decreasing the concentration gradient (A), kinetic energy (C), or surface area (D) would slow diffusion. Thus, the correct answer is B.
What is a reason why oxygen diffuses into the blood from an alveolus in the lungs?
A) The oxygen concentration in the alveolus is greater than the carbon dioxide concentration in the blood.
B) The oxygen concentration in the alveolus is greater than the oxygen concentration in the blood.
C) The oxygen concentration in the blood is greater than the oxygen concentration in the alveolus.
D) The oxygen concentration in the blood is greater than the carbon dioxide concentration in the alveolus.
▶️ Answer/Explanation
Ans: B
Oxygen diffuses from the alveolus into the blood due to a concentration gradient. The alveolus has a higher oxygen concentration than the blood, driving diffusion (B).
Option A is incorrect because diffusion depends on oxygen gradients, not carbon dioxide. Option C is false—oxygen would diffuse out of the blood if its concentration were higher there. Option D is irrelevant to the oxygen diffusion process.