Gas Exchange Surfaces

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Gas Exchange Surfaces

  1. 1. AS Level Biology Lesson 2
  2. 2. Gas exchange and respiration <ul><li>If cells are to stay active, grow and divide they need energy . </li></ul><ul><li>This energy comes from the oxidation of organic molecules such as glucose in respiration . </li></ul><ul><li>All respiration involves oxidation reactions, all cells must have a constant supply of oxygen. </li></ul>
  3. 3. 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.
  4. 4. Gas exchange <ul><li>… ..is not the same as respiration! </li></ul><ul><li>Process by which oxygen gets into cells and carbon dioxide is removed. </li></ul><ul><li>Respiration creates the constant demand for oxygen and a constant release of carbon dioxide. </li></ul>
  5. 5. Gas exchange surfaces <ul><li>Special surfaces the animals and plants have evolved to promote the exchange of gases. </li></ul><ul><li>allow the diffusion of gas into and out of cells </li></ul><ul><li>These surfaces include mesophyll layers in leaves, skin in earthworms, gills in fish and lungs in mammals.) </li></ul>
  6. 6. Features of gas exchange surfaces <ul><li>Have a large surface area relative to the volume of the organism. </li></ul><ul><li>They are thin, so have a short diffusion pathway. </li></ul><ul><li>They have a moist surface where gases can dissolve first before they diffuse in our out. </li></ul><ul><li>They are able to maintain the diffusion gradient down which the gases can diffuse. </li></ul>
  7. 7. Gas exchange in humans <ul><li>Humans have a high metabolic rate so require a fast rate of gas exchange. </li></ul><ul><li>To help with this there are two key feature that have evolved in the human system: </li></ul><ul><li>A blood transport system with red cells containing haemoglobin </li></ul><ul><li>A means of ventilation to get the gases to and from the gas exchange surface. </li></ul>

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