B3 exchange of materials

  • Created by: isobeld10
  • Created on: 08-01-15 20:27
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  • B3
    • Exchange of materials
      • Diffusion
        • The process by which particles of a move from an area of high concentration to an area of low concentration to create an even concentration
        • Example- gaseous exchange in the lungs (oxygen and carbon dioxide)
        • Factors the affect diffusion
          • Surface area
          • Distance or thickness of membrane
          • Concentration gradient
          • Permeability of surface
      • Osmosis
        • The movement of water into and out of a cell, from a dilute solution (lots of water) to a concentrated solution, across a partially permeable membrane
        • If a cell has a more dilute solution inside of the cell than out side of the cell then the cell can shrivel up
          • If this is the other way round then the cell can burst
            • Plant cells do not burst as they have turgid cell walls
      • Active transport
        • It is used in the gut when there is low concentration of nutrients in the gut but a high concentration of nutrients in the blood
        • Active transport works against the concentration gradient
        • Active transport- the transport protein carries the useful molecule and rotates using energy (from respiration) and then releases the useful molecule into the cell. The transport protein then rotates back
      • Exchange surfaces
        • Plants and animals use exchange surfaces in; digestive system, lungs, leaf and roots
        • Efficient exchange surfaces have a large surface area, thin surface, and an efficient blood supply (in animals)
      • Sports drink dilema-
        • Athletes need to replace the lost water, mineral ions and glucose that are used up in exercise
          • Sports drinks replace the lost ions that drinking water does not
            • There are often claims made by sports drink manufacturer that are not true
      • Gaseous exchange in the lungs
        • Good gaseous exchange surfaces are thin, large, moist and have good ventilation mechanism and have a good blood supply
          • Alveoli are good gas exchange surfaces
            • In the alveoli oxygen diffuses from the air into the blood supply and carbon dioxide diffuses from the blood supply into the atmosphere
    • Exchange and transport in plants
      • Exchange of water
        • Water and ions move into the plant from the roots
          • Roots have adapted to absorb water
            • Root hairs have large surface area
            • Protrusions can can penetrate between soil particles to reduce the distance the ions move
          • Water moves through osmosis
        • Transpiration is the movement of water through the xylem, from the roots to the leaf
          • Rate of transpiration increases when light intensity, temperature and air movement are increased
          • Rate of transpiration is decreased when humidity is increased as there is more water in the air and less of a concentration gradient
      • Gaseous exchange in plants
          • Function of the stoma:
            • Opens to allow diffusion of carbon dioxide into the leaf and oxygen and water vapour out of the leaf
            • Stoma closes to retain water
              • Guard cells change shape to open and close the stoma
      • Translocation
        • The transport of sugars (made through photosynthesis) through the phloem to areas of the plant to be used or stored


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