Gas Exchange

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  • Gas Exchange
    • Surfaces
      • Gas exchange occurs over a gas exchange surface
      • Two things gas exchange surfaces have in common are:
        • Large surface area
        • Thin
          • One layer of epithelial cells
        • This increases the rate of diffusion
      • A steep concentration gradient is maintained across the surface
        • increases the rate of diffusion
    • Single-celled organisms
      • Release gases through cell-surface membranes
        • By diffusion
      • No need for a specialized gas exchange system because:
        • It has a large surface area
        • It has a thin surface
          • Creating a short pathway for diffusion
    • Fish
      • Structure of gills
        • This is where the gas exchange system is located
        • Gill Fillaments
          • Thin plates
            • Give large surface area
              • Increases rate of diffusion
        • Lamellae
          • Lots of blood capillaries
            • Increases rate of diffusion
              • Thin surface layer of cells
          • Thin surface layer of cells
      • Counter-current system
        • Water with a high concentration flows next to blood with a low concentration of oxygen
          • Steep concentration gradient between water and blood
            • Oxygen diffuses from water to blood
    • Dicotyledonous Plants
      • Mesophyll cells
        • Gas exchange surface
        • Large surface area
          • Gas exchange surface
        • Inside the leaf
      • Stomata
        • Pores in epidermis
        • Gases move in and out of
        • Open to allow exchange of substances
        • Close to avoid loss of water
      • Guard cells
        • control opening and closing of stomata
    • Insects
      • Spiracles..
        • ..Pores on the
        • Air moves into trachea via these
        • CO2 moves down its own concentration gradient towards these
          • To be released into atmosphere
        • Air is moved in and out of these by
          • Rhythmic abdominal movements
      • Trachea
        • ..Pores on the
        • air-filled pipes
          • Used for gas exchange
        • Used for gas exchange
        • Tracheloes
          • Thin, permeable walls
          • Go to individual cells
    • Controlling water loss
      • Insects
        • If they are loosing too much water
          • Close spiracles
          • Have a waxy cuticle and tiny hairs around spiracles
            • Reduce evapouration
      • Plants
        • If they are loosing too much water
          • Guard cells become turgid
            • opens stomatal pore
        • If they are dehydrated
          • Guard cells become flaccid
            • Closes the stomatal pore

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