5. Partial pressure of a gas is the pressure it exerts in a mixture of gases and is equal to the total pressure of the mixture divided by the percentage of that gas in the mixture. The partial pressure of a gas is directly proportional to its concentration in the mixture.
6. The partial pressure of oxygen is expressed as Po2 while that of carbon dioxide as Pco2
7. Gas diffuses across a membrane from a region with higher partial pressure to the region with lower partial pressure