Which of the following changes in membrane components would decrease a membrane\
ID: 143535 • Letter: W
Question
Which of the following changes in membrane components would decrease a membrane's fluidity? Select all that apply. a. Replacement of phospholipids that contain unsaturated hydrocarbon tails with phospholipids that contain saturated hydrocarbon tails b. Replacement of phospholipids that contain one double bond in their hydrocarbon tails with phospholipids that contain 4 double bonds in their hydrocarbon tails C. An increase in the amount of cholesterol present in the membrane An increase in temperature e. Replacement of phospholipids that contain 15 carbons in their hydrocarbon tails with phospholipids that contain 30 carbons in their hydrocarbon tails.Explanation / Answer
Phospholipids containing shorter hydrocarbon tails are less stiff as well as less viscous because they are easily susceptible to the changes in kinetic energy due to their smaller molecular size and they have smaller surface area to undergo stabilizing van der Waals interactions with neighboring hydrophobic chains.
Phospholipids containing unsaturated hydrocarbon tails are more fluid than phospholipids that are saturated with hydrogens. On the molecular level, unsaturated double bonds make it harder for the phospholipids to pack together by inserting kinks into the hydrocarbon chain. Membranes made with such lipids have lower melting points i.e. lesser thermal energy is required to reach the same level of fluidity as membranes made with lipids containing saturated chains.
The rigid planar structure of the steroid nucleus present in cholesterol, inserted between fatty acyl side chains, reduces the freedom of neighboring acyl chains to move , forcing the chains into their fully extended conformation. Hence, the presence of sterols reduces the fluidity in the core of the bilayer. It favors the fluid state of the membrane.
It has been seen that the ratio of saturated to unsaturated fatty acid chains in the bacterial membrane decreases as the growth temperature is lowered. This decrease in the proportion of saturated residues prevents the membrane from becoming too rigid at the lower temperature.
Cells work optimally at normal physiological temperature. If body temperature of a human being increases (i.e. during a high fever), the cell membrane can become more fluid. Such phenomena occurs when the fatty acid tails of the phospholipids become less rigid and allow more movement of proteins and other molecules inside and through the membrane.
Hence,
Option A is correct.
Option B is incorrect.
Potion C is correct.
Option D is incorrect.
Option E is correct.
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