External respiration occurs between which two components?

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Multiple Choice

External respiration occurs between which two components?

External respiration is the gas exchange at the lungs where oxygen moves from the air in the alveoli into the blood, and carbon dioxide moves from the blood into the alveolar air. This happens across the thin alveolar-capillary membrane and is driven by differences in partial pressures: oxygen is more concentrated in the alveolar air than in blood, so it diffuses into the blood; carbon dioxide is more concentrated in the blood than in the alveolar air, so it diffuses out into the air to be exhaled. That pairing—alveolar air with blood—captures where external respiration occurs. The other ideas describe different processes. Gas exchange between blood and tissues is internal respiration, happening at the tissue level. The CO2 and bicarbonate pairing relates to how carbon dioxide is transported and buffered in blood, not the actual lung surface exchange. Mitochondria and cytoplasm are involved in cellular respiration inside cells, not in gas exchange between body compartments.

External respiration is the gas exchange at the lungs where oxygen moves from the air in the alveoli into the blood, and carbon dioxide moves from the blood into the alveolar air. This happens across the thin alveolar-capillary membrane and is driven by differences in partial pressures: oxygen is more concentrated in the alveolar air than in blood, so it diffuses into the blood; carbon dioxide is more concentrated in the blood than in the alveolar air, so it diffuses out into the air to be exhaled. That pairing—alveolar air with blood—captures where external respiration occurs.

The other ideas describe different processes. Gas exchange between blood and tissues is internal respiration, happening at the tissue level. The CO2 and bicarbonate pairing relates to how carbon dioxide is transported and buffered in blood, not the actual lung surface exchange. Mitochondria and cytoplasm are involved in cellular respiration inside cells, not in gas exchange between body compartments.

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