CHAP 2

Cards (21)

  • Diffusion
    The net movement of particles from a region of higher to lower concentration, down a concentration gradient
  • Diffusion
    1. Particles move from higher to lower concentration
    2. Concentration becomes equal on both sides of membrane
  • Factors affecting rate of diffusion
    • Concentration gradient
    • Diffusion distance
  • Shorter diffusion distance
    Higher rate of diffusion
  • Greater surface area to volume ratio

    Higher rate of diffusion
  • Surface area to volume ratio
    SA = length x width x 6 faces
    Volume = length x width x height
  • Cells obtain food and oxygen from all sides
  • As a cell grows larger, the rate of food and oxygen intake slows down
  • Some cells have long and narrow protrusions to increase surface area to volume ratio
  • As a cell continues to grow in size

    The growth rate slows down and stops once it reaches its optimum size
  • It is not beneficial for a cell to grow too big
  • Osmosis
    The net movement of water molecules from a region of higher to lower water potential through a partially permeable membrane
  • Factors affecting rate of osmosis
    • Water potential gradient
    • Distance over which molecules move
    • Surface area to volume ratio
  • Plant cell

    Cell sap has a lower water potential compared to solution
    Water molecules enter the cell through a partially permeable membrane
    Water in the vacuole creates turgor pressure to maintain the plant's shape
    When water leaves the cell, the cell becomes plasmolysed and flaccid
  • Animal cell

    Cytoplasm has a lower water potential than the solution
    Water molecules move out of the cell by osmosis
    The cell may burst if placed in a solution with a lower water potential than the cytoplasm
  • When a cell is placed in a solution with the same water potential, there is no net movement of water molecules in or out of the cell
  • Turgor pressure
    Maintains the shape of soft tissues in plants
    Allows non-woody plants to remain firm and erect
  • High rate of water loss from cells
    Plant wilts and loses its turgidity
  • Plasmolysis
    Causes cells to be flaccid and die if it continues for too long
  • Concentrated soil solution

    Unless sufficient water is added, the plant will eventually die
  • Water molecules move out of roots by osmosis

    Causes the plant to wilt due to water loss and evaporation from leaves