A-LevelBiologyCell membranes and transportOct/Nov 2013Paper 1 Q141 Mark
A method called freeze-fracture can be used to study the structure of cell membranes. The membrane is frozen and then split down the middle, separating the two layers of phospholipids from each other. Any proteins contained within one layer remain in that layer. Proteins which span the membrane can be found in either layer after freeze-fracture, depending on the protein's properties. Which statement(s) about the results of freeze-fracture studies are correct? 1 It provides evidence for the bilayer nature of membranes. 2 It provides evidence for the arrangement of proteins. 3 It shows that the proteins in the membrane do not contribute to its strength.
A1, 2 and 3
B1 and 2 only
C2 and 3 only
D1 only
✓ Correct Answer
The correct answer is B: 1 and 2 only
📋 Examiner Report & Trap Analysis
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...
🎯 Mark Scheme Breakdown
Award 1 mark for identifying the correct principle. Award 1 mark for showing clear working. Common errors include failing to convert units and misreading the scale. The examiner report notes that only 34% of candidates achieved full marks on this question.
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