You have 3 membrane samples: (A): A membrane in which all fatty acids have 20 ca

Question

You have 3 membrane samples: (A): A membrane in which all fatty acids have 20 carbons and are saturated; (B) A membrane in which all fatty acids have 22 carbons and are saturated (C) A membrane in which all the fatty acids have 20 carbons and each has a single double bond. You solidify the membranes and then gradually increase the temperature and record the temperature that they become fluid. The transition temperatures are: -22 oC, 33 oC, and 45 oC. (1) Assign each of the transition temperatures to the correct membrane, and explain your reasoning. (2) How would the addition of cholesterol affect this experiment?

Explanation / Answer

The composition of a membrane can effect its fluidity. Lipid chain having carbon - carbon double bonds (unsaturated) are more fluid than lipids which is saturated with hydrogrens and have single bonds. Double bond create a kink because of which neighbouring fatty acid interact legs. More carbon interaction tightly packed so less fluidity.

So membrane sample A - 33 oC

                                 B - 45 oC.

                                 C - -22 oC.

At high temperature, cholesterol performs as bidirectional regulator of membrane fluidity. It stabilizes the membrane and increases melting point. It intercalates between phospholipids, at low temperatures, prevents them from clustering and stiffening.

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