Q2. The effects of temperature and lipid composition on membrane fluidity are of

Question

Q2. The effects of temperature and lipid composition on membrane fluidity are often studied by using artificial membranes containing only one or few lipids and no proteins. Assume that you and your lab partner have made the following artificial membranes: Membrane 1: Made entirely from phosphatidyl choline with saturated 16-carbon fatty acids. Membrane 2: Same as membrane 1, except that each of the 16-carbon fatty acids has a single cis double bond. Membrane 3: Same as membrane 1, except that each of the saturated fatty acid has only 14-carbon atoms. After determining the transition temperature, you discovered that your lab partner failed to record which membranes the samples correspond to. The 3 values determined are -36oC, 23oC, and 41oC. Assign each of these transition temperatures to the correct artificial membranes and explain your reasoning.

Q3. In the middle of the winter, the membranes from a tissue sample from an organism dwelling in a pond are analyzed for their phospholipid content. In the middle of the summer, another tissue sample is taken from the same type of organism and the membrane lipid content determined. The lipid content has changed. How has it changed and why?

Explanation / Answer

Q2. Membrane 1 with 16-carbon saturated fatty acid would have high melting temperature 41oC since, it has C-C (single) bonds throughout the chain that offers the rigidity and solid state at room temperature.

Membrane 2 with also 16-carbon FA, but it has cis-double (C=C) bond that offers less rigidity and high fluidity, so that the melting temperature would be less (23oC) since it is fluid in the state.

Membrane 3 with 14-carbon FA but still it is saturated FA (C-C single bonding), it is in solid sate at room temperature, so it would need a moderate temperature that is 36oC.

membrane1 (41oC) >membrane 3 (36oC) >membrane2 (23oC)

Q3. As we know that temperature has a tremendous effect on lipid nature of the state. Membrane lipids like brown or white lipids produce variant levels of heat in the body that helps the organisms to adapt at a different temperature. For example, animals living in Antarctica have blubber (fat coat in their skin contains brown lipids (adipose) that produces heat and protects the animal from low temperature). But such a blubber coat can't be seen in tropical (high temperature) living animals, they mostly contain a low amount of white adipose tissue or fat. Low temperature solidifies the lipids and high temperature liquefies the lipids.

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