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A-LevelBiologyCell membranes and transportMay/June 2014Paper 1 Q151 Mark

Proteins in the cell surface membranes of human cells and mouse cells were labelled with red and green fluorescent dyes respectively. When a human cell and a mouse cell were fused together the red and green fluorescent labels were at first found in different regions of the cell surface membrane of the hybrid cell, but after forty minutes they were evenly distributed in the entire cell surface membrane. What explains this observation?

AAll protein molecules in the cell surface membrane are fixed to structures within the cell, but phospholipid molecules move freely between them.
BGroups of protein and phospholipid molecules in the cell surface membrane are attached to each another and move together.
COnly protein molecules in the outer layer of the cell surface membrane can move freely between phospholipid molecules.
DProtein molecules in the outer layer of the cell surface membrane and those which span the bilayer can move freely between phospholipid molecules.

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The correct answer is D. 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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About This A-Level Biology Question

This multiple-choice question appeared in the Cambridge A-Level Biology (9700) May/June 2014 examination, Paper 1 Variant 2. It tests the topic of Cell membranes and transport and is worth 1 mark.

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