1. National 5 Biology Cell Membrane

2. We are learning to: Work together as a group Context
- Carrying out a practical experiment to find out the composition of the cell membrane
Success criteria
Everyone has a job to do
You communicate effectively
You successfully find out the components of the plasma membrane

3. Background information
Beetroot contains a red pigment in the vacuole of its cells
The cell and the vacuole are surrounded by a membrane
When the membranes are damaged the red pigment leaks out of the cell

4. Why alter the temperature?
When protein is heated to high temperatures the protein changes shape
– becomes denatured
If protein is a component of the membrane when it changes shape it will cause the membrane to become leaky
- and the water in the test tubes will become pink

5. Why add acid? Acid has a similar effect on protein as temperature
When protein is added to acid the protein changes shape
Again if the acid causes the protein to change shape the membrane will become leaky
- causing the water in the test tube to become pink

6. Why add alcohol? Fat is soluble in alcohol
If the membrane contains fat the membrane will be destroyed
- causing the pigment in the vacuole to escape
- and the water in the test tube to become pink

7. What’s the purpose of the control tube?
Tube A is the control tube
This tube will show that the membrane does not become leaky on its own
Controls show the effect of the variable being changed in an investigation

8. What do your results tell you?
Write a practical report (what should it include?)
The report should include:
Title
Aim
Method
Results table
Conclusion
Evaluation – are there any improvements or changes that could be made to the experiment