RP4

• State 2 factors that affect the permeability of cell membranes.

  Temperature

  Concentration of solvents (ethanol)
• How is beetroot used to measure the permeability of cell membranes?

  The higher the permeability, the more red pigment that leaks out into the surrounding solution within a given time. A colorimeter can be used to determine the absorbance, hence concentration of pigment.
• Outline the procedure to investigate the effect of temperature on permeability of cell membrane.

  1. Cut beetroot into 6 identical cubes with a scalpel.
  2. Place each cube in a different test tube with equal volumes of distilled water.
  3. Place each test tube into water baths ranging from 30-80°

  C. Leave for 20 minutes.

  4. Filter each solution out into a cuvette and measure the absorbance using a colorimeter.
• What are the safety hazards involved in testing the effect of ethanol concentration on membrane permeability?

  Ethanol is an irritant and is flammable, keep away from naked flames, wear eye protection.

  Keep sharp scalpel away from fingers.

  Handle hot liquid with care.
• What is the effect of temperature on membrane permeability?

  Increasing temperature results in increase membrane permeability.
• What is the effect of ethanol concentration on membrane permeability?

  Increasing ethanol concentration leads to increased membrane permeability.
• How could we monitor the temperature of the water in each tube

  use a thermometer to measure temperature at regular intervals
• Why is it important to control the water volume in each tube

  if too much water has entered the pigment will be lighter as more light can pass through