Exercise 6.1 - Lipid Solubility of Membranes

LEVEL I

Materials

Procedure 1

  1. Beet cells contain a high concentration of the red pigment anthocyanin. When exposed to a compound which dissolves the cell membranes, the anthocyanin will leak out of the cells and cause a red color to occur in the surrounding media.
    Cut thin slices of a beet so that they can be placed on a microscope depression slide and viewed with the lowest power (4X).

  2. While watching the edge of the sliced beet, add approximately 1.0 ml of each of the above alcohols to the slide, until the beet section is submerged. Be careful not to allow the alcohol to flow off the slide.

    Iso-amyl alcohol has a strong, obnoxious odor and the fumes are somewhat irritating. Adequate ventilation is required.

  3. Immediately begin to time the dissolution of the beet cell membranes. Mark the time when a red color is first observed in the surrounding alcohol solution.

  4. Repeat the entire series for 1/2 and 1/4 dilutions of each of the alcohols.

  5. For each dilution of each alcohol, calculate a penetration coefficient by dividing the time of pigment appearance by the molar concentration of the alcohol. In the space given on page 137, plot this penetration coefficient against the relative miscibility of the alcohol (known as the partitition or distribution coefficient).

Alcohol
Formula
Molecular Weight
Partition coefficient
Methanol
CH_3OH
32.04
0.01
Ethanol
C_2H_5OH
46.07
0.03
n-Propanol
C_3H_7OH
60.09
0.13
n-Butanol
C_4H_9OH
74.12
0.58
n-Amyl alcohol
C_5H_1_1OH
88.15
2.00

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Cell Biology Laboratory Manual
Dr. William H. Heidcamp, Biology Department, Gustavus Adolphus College,
St. Peter, MN 56082 -- cellab@gac.edu