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Gas Exchange Surfaces
 

Gas Exchange Surfaces

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    Gas Exchange Surfaces Gas Exchange Surfaces Presentation Transcript

    • AS Level Biology Lesson 2
    • Gas exchange and respiration
      • If cells are to stay active, grow and divide they need energy .
      • This energy comes from the oxidation of organic molecules such as glucose in respiration .
      • All respiration involves oxidation reactions, all cells must have a constant supply of oxygen.
    • Respiration A series of oxidation reactions taking place in all living cells. It results in the release of energy from organic compounds such as glucose.
    • Gas exchange
      • … ..is not the same as respiration!
      • Process by which oxygen gets into cells and carbon dioxide is removed.
      • Respiration creates the constant demand for oxygen and a constant release of carbon dioxide.
    • Gas exchange surfaces
      • Special surfaces the animals and plants have evolved to promote the exchange of gases.
      • allow the diffusion of gas into and out of cells
      • These surfaces include mesophyll layers in leaves, skin in earthworms, gills in fish and lungs in mammals.)
    • Features of gas exchange surfaces
      • Have a large surface area relative to the volume of the organism.
      • They are thin, so have a short diffusion pathway.
      • They have a moist surface where gases can dissolve first before they diffuse in our out.
      • They are able to maintain the diffusion gradient down which the gases can diffuse.
    • Gas exchange in humans
      • Humans have a high metabolic rate so require a fast rate of gas exchange.
      • To help with this there are two key feature that have evolved in the human system:
      • A blood transport system with red cells containing haemoglobin
      • A means of ventilation to get the gases to and from the gas exchange surface.