diffusion

• diffusion:

  the net movement of particles from an area with a high concentration to an area with a lower concentration
• in diffusion particles move down the concentration gradient (from high to low concentration)
• diffusion is a passive process meaning no energy is required
• diffusion in humans:

  • nutrients in small intestine diffuse in the capillaries through the villi
  • oxygeon diffuses from the air into alveoli into the capiliary blood
  • carbon dioxide diffuses from the blood in the capillaries into the air into in the alveoli
  • urea diffuses from cells into the blood for excretion in the kidney
• diffusion in plants:

  • carbon dioxide used for photosynthesis diffuses into the leaves through the stomata
  • oxygen produced during photosynthesis diffuses out of the leaves through the stomata
• diffusion in fish:

  • oxygen from water passing over the gills diffuses into the blood in the gill filaments
  • carbon dioxide diffuses from the blood in the gill filaments into the water
• factors that affect the rate of diffusion:

  • difference in concentration - the steeper the concentration the faster the rate of diffusion
  • temperature - the higher the temperature the faster the rate of diffusion
  • surface area of the membrane - the larger the membrane the faster the rate of diffusion