GRE Subject Test: Biology : Understanding Membrane Structure
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Example Questions
Example Question #1 : Cell Membrane And Cell Wall
Which of the following conditions would result in a more fluid membrane?
A membrane in cold temperatures
Fully saturated fatty acid tails
Fatty acid tails with double bonds
Long fatty acid tails
Fatty acid tails with double bonds
There are many factors that determine the fluidity of cell membranes. Membranes that are composed of fully saturated, long fatty acid tails are generally less fluid then the opposite conditions. In addition, lower temperatures result in a less fluid membrane.
Membranes that have fatty acid tails with double bonds are more fluid because the double bonds make it difficult for multiple phospholipids to float next to one another. The shape of the double bond adds a another dimension to the lipid, preventing the tails from packing together. Unsaturated fatty acids are thus more fluid than saturated fatty acids.
Example Question #1 : Cell Membrane And Cell Wall
Which of the following factors would you expect to see in a cell membrane for an animal living in a very hot environment?
Longer fatty acid tails
Reduced integral proteins
More unsaturated fatty acid tails
Reduced presence of cholesterol
Longer fatty acid tails
In higher temperatures, the cell membrane is going to become increasingly fluid due to the increased movement of the phospholipids. The cell membrane can control its fluidity in high temperatures by both increasing the saturated fatty acid tail content of the phospholipids, as well as making the fatty acid tails longer. Cholesterol can also help by acting as a buffer at high temperatures.
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