exchange

• how does membrane surface area affect the rate of diffusion?

  the larger the surface area of the membrane that a substance is diffusing through, the faster the rate of diffusion.
• how does concentration gradient affect the rate of diffusion?

  the concentration gradient is linked to the difference of concentration between 2 areas. The bigger the difference in concentration between 2 areas, the greater the concentration gradient and faster the rate of diffusion.
• how does temperature affect the rate of diffusion?

  the higher the temperature, the faster the rate of diffusion.
• what are the 3 factors affecting rate of diffusion?

  • membrane surface area
  • concentration gradient
  • temperature
• do small or larger organisms normally have a high surface area to volume ratio?

  small organisms
• what can happen since small organisms have a high surface area to volume ratio?

  diffusion can happen through a large area in small organisms. This makes diffusion useful for transporting molecules through a small organism.
• what is the equation for surface area to volume ratio?

  surface area to volume ratio = surface area / ratio
• what is Fick's law?

  diffusion rate = (SA x concentration difference) / membrane thickness
• how has a thin membrane helped gas exchange (adaptation)?

  a thin membrane reduces the diffusion distance. Alveoli are one cell thick.
• how has blood supply helped gas exchange (adaptation)?

  where substances are exchanged through blood in animals, exchange surfaces are densely packed with blood vessels which replenish the blood supply to maintain a high concentration gradient by bringing in new blood as diffusion starts to even out the concentrations. There are many capillaries around the alveoli.
• how has ventilation helped gas exchange (adaptation)?

  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.
• how has a large surface area helped gas exchange (adaptation)?

  a large surface area allows more of a substance to diffuse at the same time. Alveoli create a large surface area for gas exchange in the lungs.
• what adaptations do exchange surfaces (like alveoli) have?

  • thin membrane
  • blood supply
  • ventilation
  • large surface area
• what is the purpose of alveoli?

  the alveoli (small air sacs in the lungs) are adapted for exchanging carbon dioxide and oxygen between the blood and air.
• what is the purpose of gills?

  the gills are adapted for exchanging oxygen that is dissolved in water, with carbon dioxide in a fish's bloodstream.
• what is the purpose of roots?

  roots are adapted for taking up both water and minerals from the soil around them.
• what is the purpose of leaves?

  leaves are adapted for exchanging carbon dioxide and oxygen between the leaves and the surrounding air.
• how are the lungs adapted for gas exchange?

  alveoli create a very large surface area in the lungs to allow maximum diffusion of oxygen into your blood, and carbon dioxide into the air.
• what is the small intestine adapted for?

  exchanging nutrients between digested food in the small intestine and the blood.