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 ICT IN BIOLOGY

MEMBRANE INTEGRITY IN RED CABBAGE LEAF CELLS

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.

Heat will denature proteins, including those in the cell membranes. At what temperature do red cabbage cell membranes breakdown?

MATERIALS

TI Graphing Calculator with DataMate program installed
CBL2 interface
Colorimeter sensor
10 cuvettes
Electronic water bath
Thermometer

 10 test tubes in a rack
1cm diameter cork borer
red cabbage
10cm3 syringe
Marker pen
 Pipette

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. Put the tubes in the water bath and set the temperature to 40°C. When the temperature reaches 40°C remove a tube. 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. 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

  1. Use the following steps to start the DataMate program on your calculator:
    Press     (for TI-73, 82 and 83 press ), then press the calculator key for the number that precedes DATAMATE. Press . An introductory screen will appear, followed by the main screen.
     

  2. Plug the colorimeter probe into channel CH 1 on the CBL2 interface.
  1. Start the DataMate program. Press to reset the program. DataMate will detect the sensor and display the current sensor reading.
     
  1. To calibrate the colorimeter set up a blank tube containing distilled water. Select the appropriate light source (remember red cabbage is purple) and press the calibration button on the colorimeter probe. There are four light sources to choose from: red (635nm), yellow (565nm), green (470nm) and blue (430nm).

  1. Using the cursor buttons,  or (be patient it’s a bit sluggish!) select MODE, press (scroll up to get to the last item on the menu).

 

  1.  In the SELECT MODE menu press : EVENTS WITH ENTRY.
     

  2.  Press : OK to return to the main screen.

Collecting data

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

  2. Select : START to begin data collection. Press to record your measurement. When you are asked to enter the temperature of your first sample. Press again.
     

  3. Place the next cuvette in the colorimeter and press . Then type in the next temperature. Press again and you will find the calculator producing an autoscaled scattergram of the measurements.
     

  4. Continue to take measurements of all your samples.
     

  5. You may stop data collection at any time by pressing the key.  Remember for line graphs you should have at least 5 data points (10 is even better). When you stop data collection  you will see the complete auto-scaled graph.
     

  6. To store your data, if you are satisfied with it, return to the main screen by pressing .
    Press     : TOOLS, then select : STORE LATEST DATA RUN. This stores the data in lists. In this case “temperature” in L1 and the colorimeter “absorbance” in L2 with a copy of it in L3.
    To check this press     : QUIT, then , then and, finally, select : EDIT… You will see a spread sheet with your data in it in L1, L2 (and L3).

Trouble shooting

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

(a)   Press and reboot the Datamate program.

(b)   Check the liquid that you have sampled. Is it homogeneous?

(c)   Check the cuvette that you are using is not dirty or wet on the outside.

(d)   Check the cuvette holder in the colorimeter. Is it clean and dry?

Note: You should try to keep your results between 0.050 – 0.550 absorbance. Outside this range the calibration curve is not linear. If your results are outside this range try a different wavelength (light source) or the liquid may need diluting by a known factor.

   

MOST IMPORTANT Storing your data in the calculator’s archive

If you do not do this your data will be lost. The next time you use a spread sheet the data in L1, L2 etc will get compressed.

Archiving data will remove it from the RAM memory but it will not stop it from being over-written when new data is recorded. It needs to be renamed.

To rename a list of data (e.g. L1)

1.      Select the list to be stored by pressing then then

2.      Open the LIST menu by pressing then LIST and select OPS using the cursor

3.      Descend the menu using the cursor                 to B: L
Press and type in a code name for the list. It must start with a letter so press the green key and chose a letter. Your list name can consist of one letter and four figures (try today’s date)

To archive or unarchive a list variable (L1) using a Memory Management editor

This frees up RAM memory so that you can continue recording more data.

1.      Press then MEM to display the MEMORY menu.

2.      Select 2:Mem Mgmt/Del... to display the MEMORY MANAGEMENT/DELETE menu.

3.      Select 4:List... to display the LIST menu.

4.      Press to archive L1. An asterisk (*) will appear to the left of L1 to indicate it is an archived variable.
To unarchive a variable in this screen, put the cursor next to the archived variable and press . The asterisk will disappear.

5.      Press then QUIT to leave the LIST menu.

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