alleryGas exchange between alveolar air and blood is driven by
Aactive transport requiring ATP
Bdiffusion along partial-pressure gradients
Cendocytosis
Dosmosis
Answer & Solution
Correct answer: B. diffusion along partial-pressure gradients
Pure diffusion.
O₂ moves from alveolus (high pO₂) to blood (low pO₂)
CO₂ moves the opposite way.
No energy needed — just gradients across a very thin (~0.5 μm) membrane.
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