The gradient of oxygen across the alveolar membrane is 64 mm Hg…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
The gradient of oxygen across the alveolar membrane is mm Hg. The gradient of carbon dioxide is mm Hg. Carbon dioxide is times more soluble than oxygen. Take the "push" of a gas as its gradient multiplied by its relative solubility, and take the relative solubility of oxygen as .
- Find the push of oxygen.
- Find the push of carbon dioxide.
- Does enough carbon dioxide cross the membrane? Explain.
Need a reminder? The key ideaShow
The partial pressure of a gas is its share of the total pressure: . Gases diffuse from the higher partial pressure to the lower one. The rate depends on the gradient, the solubility of the gas and the thickness of the membrane. Carbon dioxide is to times more soluble than oxygen.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Given. Gradients: and mm Hg. Relative solubilities: and .
Plan. Multiply each gradient by its relative solubility.
Step 1. (a) Oxygen: .
Step 2. (b) Carbon dioxide: .
Step 3. (c) The push of carbon dioxide is even larger than that of oxygen. So enough carbon dioxide crosses the membrane, in spite of its small gradient.
Answer: for oxygen and for carbon dioxide. Yes, enough crosses.
Check. The textbook says that carbon dioxide is to times more soluble. Using would give an even larger push.
Watch out. This is a model to show an idea. It is not a measured rate.
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