Osmosis

• Selectively permeable


  A cell membrane that allows small molecules through but not larger molecules
• Diffusion


  The movement of molecules from an area of high concentration to an area of lower concentration
• Osmosis


  The diffusion of water from a dilute solution to a more concentrated solution through a selectively permeable membrane
• What happens when water moves into a plant cell

  The plant cell becomes turgid
• What happens to a plant cell in a dilute solution? (Turgid)

  1. Vacuole expands

  2. Cell membrane pushes against cell wall

  3. Causes turgor necessary for support

  4. Cell wall stops membrane expanding too much and limits water intake
• Importance of cell wall in plant cells during osmosis


  • Prevents the expansion of the membrane to the point of bursting
• Importance of this cell type for a plant

  • It limits water intake and provides turgor necessary for support
• What happens when water moves out of a plant

  It becomes plasmolysed
• What happens to a plant cell when in a concentrated sugar solution? (Plamolysed)

  1. Plant cell loses water

  2. Vacuole becomes smaller

  3. Cell membrane pulls away from wall

  4. Cell is now plasmolysed
• What happens to red blood cells in water

  The cells will, take water in by osmosis and burst in a process called cell lysis
• Why is movement of water through a plant important?

  • Support
  • Transpiration
  • Transportation
  • Photosynthesis
• Transpiration


  The evaporation of water from the spongy mesophyll cells followed by diffusion through the leaf air spaces and the stomata
• Environmental factors that affect the rate of transpiration

  • Temperature
  • Wind speed
  • Humidity
  • Light intensity
• Factors of the leaf that can affect transpiration


  • Surface area of leaf. The greater the surface area, the greater the number of stomata and so the faster the rate of transpiration
• Temperature


  In warmer conditions water evaporates faster
• Wind speed


  Evaporation is faster in higher wind speeds as the wind rapidly removes the evaporating water away from the stomata and leaf surface and the surrounding air
• Humidity


  Humid conditions restrict evaporation as there is a decrease in the moisture gradient between the leaf surface and surrounding air
• Light


  Many plants close their stomata in darkness to reduce water loss