biology B1(b) - cells

• Active transport


  1. Movement of particles

  2. From low concentration to high

  3. Against concentration gradient

  4. Requires energy

  5. Uses specific transport protein
• Active transport in plants

  • Mineral ions from soil
• Active transport in animals

  • Last bit of glucose from the gut (most is absorbed by diffusion but when virtually all has been absorbed, there is a higher concentration of glucose in the blood)
• Osmosis


  Movement of water from high concentration of water to low OR low concentration of sugar to high, across a partially permeable membrane
• Osmosis in animals


  • No cell wall
• Osmosis in animals - hypotonic solution


  • Burst
• Osmosis in animals - isotonic solution


  • H2O in = H2O out
• Osmosis in animals - hypertonic solution


  • Shrivel up
• Osmosis in plants


  • Have a cell wall
• Osmosis in plants - hypotonic solution


  • Turgid (vacuole fills up, pushing cytoplasm against cell wall, known as turgor pressure)
• Osmosis in plants - isotonic solution


  • Flaccid (plant wilts since no turgor pressure)
• Osmosis in plants - hypertonic solution


  • Plasmolysed (cell membrane pulls away from cell wall, cells usually die)
• Dilute


  Lots of water/little sugar
• Concentrated


  Little water/lots of sugar
• Isotonic


  Same concentration
• Hypertonic solution


  Hyper means more concentrated
• Hypotonic solution


  Hypo means less concentrated
• Diffusion


  Movement of particles from a high concentration to a low concentration, for gases (always diffusion) and liquids (not water)
• Increasing diffusion into cells

  • Short diffusion path
  • One cell thick (quicker)
  • Large surface area
  • Many alveoli/lots of villi (more diffusion)
  • Maintain concentration gradient
  • Good blood supply
• Factors affecting diffusion

  • Temperature 

  Increases kinetic energy of particles

  • Concentration gradient

  The bigger the difference in concentration, the faster the rate of diffusion

  • Surface area

  The greater the surface area the more diffusion