Due to the molecules having less movement at lower temperatures, the phospholipids slowly settle into a more compact arrangement. This results in a general decrease in the fluidity of membranes. However, the presence of cholesterol in the plasma membrane produces a buffering effect on membrane fluidity.
Yeast strain X has ergosterol in its membranes, while yeast strain Z does not incorporate ergosterol into its membranes. These two yeast strains growing at 30ºC werew shifted to 20ºC. Based upon what you know about the function of cholesterol inanimal cell membranes, you would predict:
A. The membrane fluidity of strains X and Z would initially increase at the lower temperature.
B. At 20ºC, the membrane fluidity of strain Z would be greater than the membrane fluidity of strain X.
C. At 20ºC, the membrane fluidity of strain X would be greater than the membrane fluidity of strain Z.
D. A & B are correct.
E. A & C are correct.
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