A-LevelBiologyCell membranes and transport9700/12 · May/June 2017 · Q131 Mark
Proteins in the cell surface membranes of human cells and mouse cells were labelled with fluorescent dyes. The human cells were labelled with a red dye and the mouse cells were labelled with a green dye. A human cell and a mouse cell were then fused to form a hybrid cell. At first the different dyes remained separate. After 40 minutes the two dyes were evenly distributed in the hybrid 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 other 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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