4 - PERMEABILITY

• AIM?

  investigate effect of a named variable on permeability of cell-surface membranes, e.g. ethanol concentration/ temperature/ pH
• WHAT SHOULD YOU DO WHEN INVESTIGATING TEMPERATURE?

  place beetroot in same volume of distilled water to produce a solution
• WHAT SHOULD YOU MAKE SURE YOU HAVE?

  a dilution at 0% for control
• INDEPENDENT VARIABLE?

  temperature/ concentration of ethanol
• DEPENDENT VARIABLE?

  membrane permeability by absorbance of solution (colorimeter)
• CONTROL VARIABLES?

  • (temperature)
  • SA of beetroot
  • volume of solution
  • time
  • pH
• RISK ASSESSMENT?

  ethanol is flammable so keep away from naked flames
• WHAT HAPPENS TO PERMEABILITY AT HIGH TEMPERATURES?

  increases as carrier/ channel proteins denature and phospholipids have high energy so the membrane becomes more fluid
• WHAT HAPPENS TO PERMEABILITY AT LOWER TEMPERATURES?

  phospholipids have little energy so pack closely together and the membrane becomes rigid
• WHAT HAPPENS TO PERMEABILITY AT VERY LOW TEMPERATURES?

  ice crystals pierce the membrane (but not enough KE for particles to move)
• WHAT HAPPENS TO PERMEABILITY IN ETHANOL?

  phospholipids dissolve
• WHAT HAPPENS TO PERMEABILITY IN ACID?

  proteins denature