CIE IGCSE Biology

Revision Notes

11.1.4 Differences in Inspired & Expired Air

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Differences in Inspired & Expired Air

  • Air that is breathed in and air that is breathed out has different amounts of gases in it due to exchanges that take place in the alveoli
  • Atmospheric air contains around 20 – 21% oxygen, of which we only absorb around 4 – 5%, breathing out air containing around 16% oxygen
  • Normal carbon dioxide content of air is around 0.04% and, as carbon dioxide diffuses into the alveoli from the blood, we breathe out air containing around 4% carbon dioxide
  • The air we breathe out contains more water vapour than when we breathe it in, and the temperature of exhaled air is higher than inhaled air

Composition of Air Table Differences between Inhaled & Exhaled Air table, IGCSE & GCSE Biology revision notes

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Author: Lára

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.