Practical 3

Describe and explain the effect temperature has on permeability

As temperature increases, permeability increases. This is because as temperature increases, kinetic energy increases which causes the phospholipids to move so they are not as tightly packed. The increased temperature also causes proteins to denature which increases permeability. Water molecules also gain energy which causes them to expand and put pressure on the cell membrane, damaging it and making it more permeable.

Describe and explain the effect alcohol concentration has on membrane permeability

As alcohol concentration increases, permeability increases. This is because the alcohol absorbs the lipids in the membrane, damaging it and making it more permeable

Method for investigating the effects of temperature on cell membrane permeability

Use a cork borer to remove parts of the beetroot. Cut the beetroot into 3 1cm tall cylinders. Rinse the excess pigment off with water. Add each beetroot piece into a separate beaker with the same volume of distilled water. Place into a water bath of a set temperature and wait 20 minutes. After 20 minutes remove the beetroot and use a pipette to transfer the water with pigment into separate cuvettes. Use a cuvette with distilled water to calibrate the colorimeter. Use the colorimeter to measure the absorbance of each cuvette and record results and calculate a mean. Repeat with 5 different temperatures

Method for investigating the effects of alcohol concentration on membrane permeability

Use a cork borer to remove parts of the beetroot. Cut the beetroot into 3 1cm tall cylinders. Rinse the excess pigment off with water. Add each beetroot piece into a separate beaker with the same volume of your alcohol concentration and wait 20 minutes. After 20 minutes remove the beetroot and use a pipette to transfer the water with pigment into separate cuvettes. Use a cuvette with distilled water to calibrate the colorimeter. Use the colorimeter to measure the absorbance of each cuvette and record results and calculate a mean. Repeat with 5 different alcohol concentrations