Biology 9700 · AS & A Level · Fluid mosaic membranes

Fluid mosaic membranes — practice question

High concentrations of ethanol can disturb the arrangement of the cell membrane and make the cell surface membrane leaky. Yeast cells produce ethanol as a waste product of metabolism. Yeast cells are able to change the composition of the cell surface membrane to lessen the effect of ethanol. • Saturated fatty acid, X, is substituted with unsaturated fatty acid, Y. • Y has a shorter hydrocarbon chain than X. • The phospholipid to protein ratio increases. Which statement would explain why the effect of ethanol is reduced?

  • AA greater proportion of phospholipid may increase the entry of ethanol via channel proteins.
  • BAn increase in hydrophobic interaction by phospholipid tails improves membrane stability.
  • CAn increase in the proportion of fatty acids with double bonds decreases membrane fluidity.
  • DThe shorter hydrocarbon chain of Y decreases membrane fluidity.

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