Membrane permeability

• What are cell-surface membranes primarily made of?

  Phospholipid bilayer
• What does selectively permeable mean in relation to cell membranes?

  It allows certain substances to pass through
• Which variables can change membrane permeability?

  Temperature and concentration of solvents
• What pigment do beetroot cells contain?

  Betalain
• How can membrane permeability be measured using beetroot cells?

  By measuring the amount of pigment leaked
• What equipment is used to measure absorbance in this experiment?

  Colorimeter
• What is the method for measuring beetroot cell membrane permeability?

  1. Cut beetroot into identical cylinders.
  2. Place in distilled water at various temperatures.
  3. Leave for 15 minutes to allow pigment leakage.
  4. Measure absorbance using a colorimeter.
• What is the purpose of using a thermometer in the experiment?

  To record the exact temperature of the water bath
• What does a higher absorbance indicate in this experiment?

  Higher pigment concentration and more permeability
• What are the risks associated with the experiment and their precautions?

  • Scalpel: Cut away from fingers; use forceps.
  • Broken glass: Handle carefully; keep away from edges.
  • Hot liquids: Use tongs; wear eye protection.
  • Ethanol: Wear eye protection; avoid flames.
• What happens to membrane permeability as temperature increases?

  It increases due to protein denaturation
• Why does low temperature decrease membrane permeability?

  Phospholipids are packed closely together
• What can form at very low temperatures that affects membrane permeability?

  Ice crystals
• How can the method be modified to investigate ethanol's effect on membrane permeability?

  • Use ethanol concentration as the independent variable.
  • Higher ethanol concentrations cause more membrane disruption.
  • More gaps form, increasing permeability.
• What is the effect of higher concentrations of ethanol on the cell membrane?

  They cause more disruption and gaps
• What is the relationship between temperature and membrane permeability?

  Higher temperature increases permeability
• What happens to proteins in the membrane as temperature increases?

  They denature and lose their structure
• What is the purpose of plotting a graph of absorbance against ethanol concentration/temperature?

  To visualize the relationship between variables