Multiple choice

Exchange of gases in lung alveoli occurs through

  1. active transport

  2. osmosis

  3. simple diffusion

  4. passive transport

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Gas exchange in alveoli occurs by simple diffusion - oxygen moves from alveolar air (higher PO2) into blood (lower PO2), and CO2 moves from blood (higher PCO2) into alveoli (lower PCO2). This is passive movement down concentration gradients without energy expenditure. Osmosis is water movement, active transport requires energy, and passive transport is a broader category.

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