Red cabbage leaf epidermal cells are pigmented purple with anthocyanins. The pigments are held in their sap vacuoles. If the membranes of the cell are damaged these pigments will leak from the cell.

What will be the effect of heat on the membranes of red cabbage tissue?

MATERIALS

METHOD

1. Cut discs from the red cabbage and select 30 which are of uniform thickness. Place three discs in each test tube and add 10cm³ of distilled water to each tube.
   
2. the tubes in the water bath and set the temperature to 40°C. When the temperature reaches 40°C remove a tube. Monitor the temperature of the water using a thermometer or a temperature probe. Continue raising the temperature and remove a tube at 5°C intervals.
   
3. Suck up liquid from a test tube and fill a colorimeter cuvette until it is 1 cm from the top (about 2/3rds full). Wash the pipette, take a sample from the next tube and fill a fresh cuvette. When labelling the cuvettes mark one side only near the top. Handle the cuvettes near the top too.

Starting the DataMate Program and calibrating the sensor

KEEP YOUR LIQUIDS AWAY FROM THE COMPUTER AND ITS MOUSE

1. Connect the LabPro interface to the mains via the mains adaptor. Connect the LabPro to the US-B socket of the computer.
   
   

2. Plug the colorimeter probe into channels CH 1on the LabPro interface.

3. Start the Logger Pro program. Logger Pro will detect the auto-ID sensor, set the data collection parameters, and display the current sensor reading.
   
   Remove the graph window leaving the data set spread sheet alone.

4. Click on Setup icon to open the data collection menu. Select Mode and choose Events with entry. The Column entry is Temperature and the Unitsare °C
   Click Done.

5. To calibrate the colorimeter set up a blank tube containing distilled water. Select the appropriate light source. Remember red cabbage is purple. This is the light that is transmitted. You want to choose a wavelength of light that is absorbed by the liquid.
   
   Press the calibration button on the colorimeter probe. A LED will flash on the colorimeter to show it is calibrating.

Collecting data

1. Put a cap on the cuvette with the first sample. Set the cuvette in the colorimeter, take care not to touch the sides where the light will pass.

2. When everything is ready:

   Select Collect (the green arrow) to begin data collection.
   Click on the wheel symbol Keep current value. Enter the temperature the sample was heated to and click Done.

3. Remove the cuvette and replace it with the next. Collect the data for every 5°C from 40 to 80°C. The data will appear in the spread sheet of the data set. Click on Stop to end the data collection.
   
   DO NOT LEAVE THE LAST CUVETTE IN THE COLORIMETER

4. Copy the data set. Present your data in an appropriate way, process the data to determine the effect of temperature on the membranes of this tissue. Discuss and evaluate your results.

Trouble shooting

If you get readings that appear strange or impossible try the following:

1. Check the liquid that you have sampled. Is it homogeneous and transparent?

2. Check the cuvette that you are using is not dirty or wet on the outside.

3. Check the cuvette holder in the colorimeter. Is it clean and dry?

• Top of Page

© Paul Billiet 2010