The partial pressures (in mm Hg) of oxygen $(O_{2})$ and carbon dioxide $(C O_{2})$ at alveoli (the site of diffusion) are:

p O_{2} = 159 a n d p C O_{2} = 0.3

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p O_{2} = 104 and p C O_{2} = 40

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p O_{2} = 40 and p C O_{2} = 45

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p O_{2} = 95 and p C O_{2} = 40

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Solution

The correct option is B $p O_{2} = 104 and p C O_{2} = 40$
The pressure exerted by an individual gas in a mixture is known as its partial pressure. A gas will move from a region where its partial pressure is higher to a region where its partial pressure is lower.

Partial pressure of oxygen ( $p O_{2}$ ) in alveolar air is higher (104 mm of Hg) as compared to the partial pressure of carbon dioxide ( $p C O_{2}$ ) (40 mm of Hg).

In the deoxygenated blood, partial pressure of oxygen is lower (40 mm of Hg) as compared to partial pressure of carbon dioxide (45 mm of Hg).

Due to this difference in the partial pressures of oxygen between alveolar air and deoxygenated blood, oxygen diffuses from the alveoli into the blood capillaries.

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Similar questions

Q. Assertion :Partial pressure of

O_{2}

in the alveoli is 104 mm Hg. Reason: Partial pressure of

O_{2}

is dependent upon concentration of

C O_{2}

If the partial pressures of oxygen and carbon dioxide in the alveoli are 104 and 40 and in the blood reaching the alveoli at that moment it is 40 and 45 respectively, then oxygen and carbon dioxide will diffuse from

Q. Partial pressures of oxygen and carbon dioxide in healthy human lung alveoli are respectively, nearest to.

Q. Partial pressures of

C O_{2}

at alveoli and oxygenated blood are, respectively (in mmHg)

Respiratory gas	Atmospheric air	Alveoli
$O_{2}$	159	A
$C O_{2}$	0.3	B

The table given shows the partial pressure values (in mm Hg) of oxygen and carbon dioxide in the alveoli in comparison to that in atmospheric air. Identify A and B and choose the correct option accordingly.

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The partial pressures (in mm Hg) of oxygen (O2) and carbon dioxide (CO2) at alveoli (the site of diffusion) are:

The partial pressures (in mm Hg) of oxygen $(O_{2})$ and carbon dioxide $(C O_{2})$ at alveoli (the site of diffusion) are: