Exchange surfaces

• In a single cell organism, gases and dissolved substances can diffuse directly into the cell across the cell membrane because they have a larger surface area compared to the volume so enough substances can be exchanged across the membrane supplies the volume of the cell
• Exchange services are adapted to maximise effectiveness


  • They have a thin membrane, so substances only have a short distance to diffuse
  • They have a large surfaces areas or lots of substances can diffuse at once
  • Exchange surfaces in animals have lots of blood vessels, to get stuff into an out of the blood quickly
  • Gas exchange surfaces in animals are often ventilated