Exchange Surfaces
Biology: AQA GCSE Higher, topic 1.3.5
Exchange Surfaces
Exchange surfaces are surfaces that are adapted to maximise the efficiency of gas and solute (a substance dissolved in a liquid) exchange across them. They have the following adaptations:
Large surface area
- A large surface area allows more of a substance to diffuse at the same time.
Thin membrane
- A thin membrane reduces the diffusion distance.
Blood supply
- Where substances are exchanged through blood in animals, exchange surfaces are densely packed with blood vessels:
- These blood vessels replenish the blood supply to maintain a high concentration gradient by bringing in new blood as diffusion starts to even out the concentrations.
Ventilation
- In animals, if a gas is exchanged, the surface is ventilated (through breathing) to maintain a high concentration gradient and increase the rate of exchange.
Test yourself on Exchange Surfaces
Why does a large surface area increase the rate of diffusion across an exchange surface?
Why does a thin membrane increase the rate of diffusion across an exchange surface?
When are exchange surfaces adapted with ventilation rather than a dense network of blood vessels?
What would happen to the rate of diffusion across an exchange surface if its surface area decreased?
What would happen to the rate of diffusion across an exchange surface if its membrane became thicker?