A-LevelBiologyCell membranes and transport9700/12 · May/June 2014 · 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.
✓ Correct answer
D: Protein 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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