Biology B3.1

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  • Biology B3.1
    • Osmosis
      • Water diffuses from a dilute solution to a more concentrated solution through a partially permeable membrane
      • Is the diffusion of water
      • Water moves into or out of cells by osmosis through the cell membrane
    • Active transport
      • Active transport allows cells to take in substances against a concentration gradient
      • Active transport uses energy from respiration
      • Ions, from dilute solutions, and other substances such as sugar can be absorbed by active transport
    • Sports drinks
      • Most soft drinks contain
        • Water to replace water lost when sweating
        • Sugar to replace sugar used for energy release in exercise
        • Mineral ions to replace those lost in sweating
      • For normal levels of exercise, water is likely to be as effective as a sports drink
    • Exchanging materials - the lungs
      • Large organisms need exchange surfaces
      • Exchange surfaces have features to make them efficient
      • The lungs are adapted to be an efficient exchange surface
    • Ventilating the lungs
      • The breathing system is designed to move air in and out of the lungs
      • Ventilation occurs due to changes of pressure inside the chest
    • Articicial breathing aids
      • Some people cannot get enough oxygen into their bloodstream
        • If alveoli are damaged
        • If tubes leading to the lungs are narrowed, less oxygen can be moved through them
    • Exchange in the gut
      • The villi are an efficient exchange surface for the absorption of the soluble products of digestion by diffusion or active transport
      • Villi provide a large surface area and have a good blood supply
      • Villi line the inner surface of the small intestine
    • Exchange in plants
      • The stomata in plants leaves allow carbon dioxide to diffuse into the leaf from the atmosphere
      • Leaves are flat and thin with internal air spaces to increase the surface area for diffusion of gases
      • Root hair cells increase the surface area of roots
    • Transpiration
      • Water is lost from the leaves by evaporation
      • The water vapour escapes the leaf through the stomata when they open to allow carbon dioxide to enter the leaf
      • Wilting can protect the leaf from excessive water loss


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