diffuse down their partial pressure gradients.
= Pressure of a particular gas in a mixture.
Partial pressure = fractional composition of a particular gas in the mixture x the total pressure exerted by the mixture.
- Air pressure at sea level = 760mm Hg
- PO2 = 0.21 x 760 = 160 mm Hg
- PCO2 = 0.0003 x 760 = 0.29 mm Hg
Gases in the air dissolve in water until they reach equilibrium, at which their partial pressure in the water is the same as their partial pressure in the air (e.g. water at sea level has a PO2
of 160 mm Hg).
However, the concentration
of O2 is much lower in water than in air, because O2
is much less soluble in water than it is in air.