Exercise 6.1 - Lipid Solubility of Membranes

LEVEL I

Materials

• Fresh beets
• Solutions of the following alcohols:
  • 22 M Methanol
  • 8.5 M Ethanol
  • 3.0 M n-Propanol
  • 1.1 M n-Butanol
  • 0.38 M Amyl alcohol (Optional)
• Razor blades
• Depression slides
• Stopwatch
• Microscope

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	CHOH	32.04	0.01
Ethanol	CHOH	46.07	0.03
n-Propanol	CHOH	60.09	0.13
n-Butanol	CHOH	74.12	0.58
n-Amyl alcohol	CHOH	88.15	2.00

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