The Human Respiratory System · NCERT Biology

The partial pressure of oxygen ($pO_2$) in the alveolar air and deoxygenated blood is respectively:

  1. 104 mm Hg and 40 mm Hg
  2. 40 mm Hg and 104 mm Hg
  3. 95 mm Hg and 40 mm Hg
  4. 45 mm Hg and 40 mm Hg
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Correct answer: 104 mm Hg and 40 mm Hg

In the alveoli, the $pO_2$ is 104 mm Hg, which is higher than the $pO_2$ in deoxygenated blood (40 mm Hg). This gradient allows oxygen to diffuse from the alveoli into the blood.

Difficulty: Medium Question 15 of 20

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