Which statement best describes alveolar gas exchange?

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Multiple Choice

Which statement best describes alveolar gas exchange?

Gas exchange in the alveoli occurs by simple diffusion driven by partial pressure gradients. Oxygen moves from the alveolar air, where its partial pressure is high, into the blood of the pulmonary capillaries, where its partial pressure is lower. At the same time, carbon dioxide moves from the blood, where its partial pressure is higher, into the alveolar air to be exhaled, because the alveolar air has a lower partial pressure of CO2. This exchange happens across the thin respiratory membrane without requiring energy. So the correct description is that oxygen diffuses into the blood from the alveoli, and carbon dioxide diffuses from the blood into the alveoli. The idea that gas exchange requires active transport is not accurate for this process.

Gas exchange in the alveoli occurs by simple diffusion driven by partial pressure gradients. Oxygen moves from the alveolar air, where its partial pressure is high, into the blood of the pulmonary capillaries, where its partial pressure is lower. At the same time, carbon dioxide moves from the blood, where its partial pressure is higher, into the alveolar air to be exhaled, because the alveolar air has a lower partial pressure of CO2. This exchange happens across the thin respiratory membrane without requiring energy. So the correct description is that oxygen diffuses into the blood from the alveoli, and carbon dioxide diffuses from the blood into the alveoli. The idea that gas exchange requires active transport is not accurate for this process.

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