A-LevelBiologyCell membranes and transportOct/Nov 2019Paper 1 Q171 Mark
High concentrations of ethanol can disrupt cell membrane structure and make the cell surface membrane leaky. Yeast cells release ethanol as a waste product of metabolism. Yeast cells can alter the composition of the cell surface membrane to reduce the effect of ethanol. • A saturated fatty acid, X, is replaced by an unsaturated fatty acid, Y. • Y has a shorter hydrocarbon chain than X. • There is an increase in the phospholipid to protein ratio. Which statement would explain why the effect of ethanol is reduced?
Agreater 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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The correct answer is B. This question tests the candidate's understanding of cell membranes and transport within the Biologysyllabus. The examiner's mark scheme requires...
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Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
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