In an experiment, fluorescent dyes were used to tag proteins on the outer surface of cell surface membranes. Living human cells were marked with one colour of fluorescent dye and mouse cells with a different colour of fluorescent dye. A human cell and a mouse cell are then fused to make a hybrid cell. Initially, the two fluorescent labels stay separate, but after 40 minutes they are spread at random across the hybrid cell surface membrane. What does this experiment show?
- AProteins are found only on the outer surface of cell surface membranes.
- BProteins in the outer layer of a bilayer do not penetrate into the inner layer.
- CProteins move freely in the phospholipids of a bilayer.
- DThe cell surface membranes of the two cells are bilayers.