Gas exchange, cell membranes and transport

• What are the properties of a gas exchange surface?

  High surface area:volume

  Short diffusion pathway Large concentration gradient
• How does the structure of the lungs allow for efficient gas exchange?

  Alveoli
• how do alveoli increase the rate of diffusion

  high concentration gradient maintained by a constant blood supply and ventilation

  high surface area as alveoli are small, meaning there is many of them, extensive capillary network

  membrane is one cell thick and moist
• Why do organisms need exchange surfaces

  Large multicellular organisms have a very small surface area to volume ratio

  removal of waste and exchange of gas cannot happen by simple diffusion due to very large diffusion distance
• What is Fick’s law

  rate of diffusion = (surface area x concentration difference) /thickness of membrane
• How can rate of diffusion be doubled in terms of Fick’s law

  Surface area of concentration difference doubles

  or diffusion pathway halves