Core Practical 3

Question 1

What are the factors that affect the permeability of cell membrane

Answer 1

• Temperature
• pH
  Beetroot can be used to investigate the permeability
  As permeability increases the more pigment leaks

Question 2

How is the amount of pigment measured

Answer 2

By using a colourimeter

Question 3

How to investigate the effect of temperature on the permeability

Answer 3

Independent variable: temperature or alcohol concentration
Dependent variable: the intensity of the colour
- cut five pieces of beetroot by using a cork borer and scalpel which must have the same surface area and volume
- rinse the excess of beetroot pigment
- add the beetroots to test tubes with the same volume of water
- put each test tube in water bath at different temperatures for the same set of time
- remove the beetroots and put a sample of the colour to the colorimeter
- the higher the absorbance of water the higher the pigment released due to a greater permeability

Question 4

What are the results of this investigation

Answer 4

• as the temperature increases membrane permeability also increases hence that phospholipids will have more kinetic energy which will result in the movement and increase in the permeability

Question 5

What are the limitations

Answer 5

• cuvettes may differ in thickness
  Solution: use the same cuvettes
• the beetroot may not be indentical
  Solution: repeat the experiment

Question 6

What are the results of investigating the experiment with alcohol

Answer 6

• as alcohol concentration increases the permeability of the membrane increases because alcohol dissolves the membrane