Features of Gas Exchange Surfaces (Cambridge (CIE) O Level Biology): Revision Note
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Features of Gas Exchange Surfaces
The surfaces where gas exchange occurs in an organism are highly varied
Different organisms have evolved mechanisms for getting the gases to the gas exchange surface depending on size, habitat etc.
All gas exchange surfaces have features in common
These features allow the maximum number of molecules to be exchanged across the surface in the shortest period of time
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
Gas Exchange in the Alveolus Diagram
The alveolus is the gas exchange surface in humans
Examiner Tips and Tricks
You may notice that several of the features of alveoli that make them suited to their function are the same as those that make villi suited to their function, or root hair cells suited to their function – the reason for this is because all of these structures are involved in transporting substances across their surfaces – by diffusion, active transport, osmosis or a combination.
So if you learn the features of one, you also know many of the features of the others!
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