5. The effects of temperature and lipid composition on membrane fluidity are oft

Question

5. The effects of temperature and lipid composition on membrane fluidity are often studied by using artificial membranes containing only one or a few kinds of lipids and no proteins. Assume that you and your lab partner have made the following artificial membranes: Membrane 1: Made entirely from phosphatidylcholine with stearic acid as the fatty acids. -Membrane 2: Same as membrane 1, except that each of the fatty acids is oleic acid. Membrane 3: Same as membrane 1, except that each of the fatty acids is elaidic acid. After determining the transition temperatures (T) of samples representing each of the membranes, you discover that your lab partner failed to record which membranes the samples correspond to. The three values you determined are 69.6°C, 13.4°C, and 45.3°C Assign each of these transition temperatures to the correct artificial membrane above. (3 pts) 6. Gorter and Grendel's (Ch. 7 of text) classic conclusion that the plasma membrane of the human erythrocyte consists of a lipid bilayer was based on the following observations () the lipids they extracted with acetone from 4.74 x 10° erythrocytes formed a monolayer 0.89 m2 in area when spread out on a water surface; (ii) the surface area of one erythrocyte was about 100 m, according to their measurements. Show (mathematically) from these data how they came to the conclusion that the erythrocyte membrane is a bilayer. Explain your answer. (5 pts)

Explanation / Answer

5.
Membrane 1: Made entirely from phosphatidylcholine with stearic acid as the fatty acids. 69.6 degree C
Membrane 2: Same as membrane 1, except that each of the fatty acids is oleic acid. 13.4 degree C
Membrane 3: Same as membrane 1, except that each of the fatty acids is elaidic acid. 45.3 degree C

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