Neco 2018 Biology Question 17

The diagram shows a labelled cross‑section of an alveolus surrounded by a dense capillary network. The diffusion coefficient for oxygen across the alveolar membrane is \(D=0.20\ \text{cm}^{3}\,\text{mmHg}^{-1}\,\text{min}^{-1}\).\n\nAt sea level the partial pressure of O\(_2\) in the alveolar air is \(P_{A}=100\ \text{mmHg}\) and in the pulmonary capillary blood it is \(P_{c}=40\ \text{mmHg}\).\n\n(a) Using Fick's law, calculate the rate of O\(_2\) diffusion (in cm\(^3\) per minute) from the alveolus into the blood.\n\n(b) If the individual ascends to a high altitude where the alveolar \(P_{A}\) falls to 70 mmHg while \(P_{c}\) remains 40 mmHg, what is the new diffusion rate?