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Computer Interfacing

The Effect of Alcohol on Biological Membranes


1. Obtain and wear goggles, an apron, and gloves.

2-6. Prepare your alcohol solutions.

7-8. Prepare the beet for the experiment.

9. Start the timer. Use forceps to place a piece of beet root in each of 18 well plates, as shown in Figure 2. Stir the beet in the alcohol solution once every minute with a toothpick. Be careful not to puncture or damage the beet.

10. After 10 minutes, remove the beet pieces from the wells. Remove them in the same order that they were place in the well. Discard the beet pieces and retain the colored solutions.

11. Prepare the computer for data collection.

12. Now calibrate the colorimeter.

13. You are now ready to collect absorbance data for the alcohol solutions.

  • Click on the Start button.
  • Empty the water from the cuvette. Use a cotton swab to dry the cuvette after the water has been emptied from it.
  • Add all of the 0% methanol solution from Well 1 into the cuvette. Wipe the outside with a tissue and place it in the colorimeter. After closing the lid, wait for the absorbance value displayed on the monitor to stabilize.
  • Click on the Keep button, enter "0" in the Concentration edit box, and click on the OK button. The data pair you just collected should now be plotted on the graph.
  1. Collect absorbance data for the 20% alcohol solution:
    • Discard the cuvette contents into your waste beaker.
    • Remove all of the solution from the cuvette. Use a cotton swab to dry the cuvette.
    • Fill the cuvette with the 20% methanol solution from Well 2.
    • Wipe the outside, place it in the colorimeter, and close the lid.
    • When the absorbance value stabilizes, click on the Keep button .
    • Enter "20" in the Concentration edit box.
    • Click on the OK button.

15. Repeat Step 14 to save and plot absorbance and concentration values of the solutions in wells 3, 4, 5, and 6. When you have finished with all of the methanol solutions, click on the Stop button.

16. Choose Data A Table from the Windows menu. Record the absorbance and concentration data pairs in the Data and Calculations table. When you are finished recording the numbers, close the Data A Table window.

17. Clear the data by selecting Clear Data A from the Data menu.

18. Repeat Steps 13 through 17, measuring the six ethanol solutions.

19. Repeat Steps 13 through 17, measuring the six 1-propanol solutions.

20. Make a graph of your data. Put the alcohol concentration on the x axis and the absorbance on the y axis. Plot the six methanol measurements and connect them with a line. Using the same graph, plot the six ethanol measurements and connect them with a line. Do the same with the six propanol measurements.

21. Use you graph to answer the discussion questions.

22. Discard the solutions as directed by your teacher.

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