In alveolar air, the partial pressure of $C O_{2}$ is

40 mm of Hg

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42 mm of Hg

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44 mm of Hg

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46 mm of Hg

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Solution

The correct option is A 40 mm of Hg
Alveoli are the primary sites of the exchange of gases. Exchange of gases also occurs between blood and tissues.
Oxygen and carbon dioxide are exchanged in these sites by simple diffusion mainly based on pressure/ concentration gradient.
Pressure contributed by an individual gas in a mixture of gases is called partial pressure and represented by pO $_{2}$ for oxygen and pCO $_{2}$ for carbon dioxide.
Partial pressures of these two gases in the atmospheric air are 159 and 0.3 mm of Hg and in the alveoli 104 and 40 mm of Hg while in tissues the values are 40 and 45 respectively.
Therefore, the correct answer is option A.

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In alveolar air, the partial pressure of CO2 is

In alveolar air, the partial pressure of $C O_{2}$ is