Differences in Inspired & Expired Air (Cambridge (CIE) IGCSE Biology): Revision Note
Exam code: 0610 & 0970
Differences in inspired & expired air
Air that is inhaled, or breathed in, differs in its gas composition to air that is exhaled, or breathed out; this is due to the process of gas exchange that takes place in the alveoli
Inhaled air can also be referred to as inspired air
Exhaled air is also known as expired air
Inhaled air is drawn from the surrounding atmosphere, and so its gas composition matches atmospheric levels
During gas exchange in the alveoli oxygen enters the blood from the alveoli, and carbon dioxide and water vapour leave the blood and enter the alveoli
This gas exchange process means that the gas composition of exhaled air differs to that of the air that was previously inhaled
Inhaled air contains around 21 % oxygen and exhaled air contains around 16 % oxygen
Inhaled air contains around 0.04 % carbon dioxide and exhaled air contains around 4 % carbon dioxide
Inhaled air contains less water vapour than exhaled air
Composition of inhaled and exhaled air table
Gas | Inspired air / % | Expired air / % |
|---|---|---|
Oxygen | 21 | 16 |
Carbon dioxide | 0.04 | 4 |
Water vapour | 0.2 - 4 | 1 - 5 |
Nitrogen | 78 | 78 |
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