IGCSEBiologyCambridge (CIE)Revision Notes11. Gas Exchange in HumansGas Exchange in HumansFeatures of Gas Exchange Surfaces

Features of Gas Exchange Surfaces (Cambridge (CIE) IGCSE Biology): Revision Note

Exam code: 0610 & 0970

Lára Marie McIvor

Written by: Lára Marie McIvor

Reviewed by: Jenna Quinn

Updated on

Cambridge (CIE) BiologyCambridge (CIE) Combined Science: Biology

Features of gas exchange surfaces

  • All gas exchange surfaces have features in common

  • These features maximise the rate of gas exchange taking place; they include:

    • large surface area to allow faster diffusion of gases across the surface

    • thin walls to ensure diffusion distances remain short

    • good ventilation with air so that diffusion gradients can be maintained

    • good blood supply to maintain a high concentration gradient so diffusion occurs faster

Diagram of gas exchange in an alveolus showing air flow, CO₂ diffusing out of the blood into the alveolus, O₂ diffusing into the blood from the alveolus, capillaries transporting blood that has been oxygenated away from the alveolus, linked to the lungs and the heart
The alveolus is the gas exchange surface in humans

Examiner Tips and Tricks

You may notice that several of the features of alveoli that aid their function are the same as those that make villi, or root hair cells, suited to their function, e.g.

  • large surface area

  • good blood supply

  • steep concentration gradient

These structures are all examples of exchange surfaces; they allow the efficient movement of substances across their surface by diffusion, active transport and/or osmosis. So, if you learn the features of one exchange surface, you also know the features of the others!

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Lára Marie McIvor

Author: Lára Marie McIvor

Expertise: Content Creator

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.

Jenna Quinn

Reviewer: Jenna Quinn

Expertise: Content Creator

Jenna studied at Cardiff University before training to become a science teacher at the University of Bath specialising in Biology (although she loves teaching all three sciences at GCSE level!). Teaching is her passion, and with 10 years experience teaching across a wide range of specifications – from GCSE and A Level Biology in the UK to IGCSE and IB Biology internationally – she knows what is required to pass those Biology exams.