Question

Partial pressure of Co, in inspired and expired air
are and respectively
(1) 159 and 116 mm of Hg
(2) 40 and 45 mm of Hg
(3) 0.3 and 45 mm of Hg
(4) 0.3 and 32 mm of Hg

Answer 1

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 pO2 for oxygen and pCO2 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.