The Effect of Alcohol on Biological Membranes

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The Effect of Alcohol on Biological Membranes

Procedure

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

2. Obtain the following materials:

a. Place about 10 mL of methanol in a medium sized test tube. Label this tube M.

b. Place about 10 mL of ethanol in a medium sized test tube. Label this tube E.

c. Place about 10 mL of 1-propanol in a medium sized test tube. Label this tube P.

d. Place about 30 mL of tap water in a small beaker.

3. Prepare five methanol solutions (0%, 10%, 20%, 30% and 40%). Using Beral pipets, add the number of drops of water specified in Table 1 to each of five wells.  Use a different Beral pipet to add alcohol to each of five wells in the microwell plate. See Table 1 to determine the number of drops of alcohol to add to each well.

4. Clean the pipet used to transfer alcohol. To do this, wipe the outside clean and empty it of liquid. Draw up a little ethanol into the pipette and use the liquid to rinse the inside of the pipette. Discard the ethanol.

5. Prepare five ethanol solutions. To do so, repeat Step 3, substituting ethanol for methanol. Place each solution in the second row of wells. See Figure 1.

6. Prepare five 1-propanol solutions. To do so, clean your pipette and repeat Step 3, substituting 1-propanol for methanol. Place each solution in the third row of wells. See Figure 1.

 7. Now, obtain a piece of beet from your instructor. Cut 15 squares, each 0.5 cm X 0.5 cm X 0.5 cm in size. They should easily fit into a microwell without being wedged in. While cutting the beet, be sure:

• There are no ragged edges.

• No piece has any of the outer skin on it.

• All of the pieces are the same size.

• The pieces do not dry out.

 8. Rinse the beet pieces several times using a small amount of water. Immediately drain off the water. This will wash off any pigment released during the cutting process.  

9. Set the timer to 10 minutes and begin timing. Use forceps to place a piece of beet into each of 15 wells, as shown in Figure 1. Stir the beet in the alcohol solution once every minute with a toothpick. Be careful not to puncture or damage the beet. While one team member is performing this step, another team member should proceed to Step 10.

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10. Connect the Colorimeter to the computer interface and prepare the computer for data collection by opening the file “08 Alcohol and Membranes” from the Biology with Vernier folder of LoggerPro.

11. Prepare a blank by filling a cuvette 3/4 full with distilled water.

12. Calibrate the Colorimeter.

13.  After the 10-minute period is complete, remove the beet pieces from the wells. Remove them in the same order that they were placed into the wells.

14. Discard the cuvette contents into your waste beaker. Remove all of the solution from the cuvette. Use a cotton swab ...

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