Proteins in the cell surface membranes of human cells and mouse cells were tagged using fluorescent dyes. The human cells received a red dye, whereas the mouse cells received a green dye. A human cell and a mouse cell were then joined to produce a hybrid cell. Initially, the two dyes stayed separate. After 40 minutes, both dyes were distributed uniformly throughout the hybrid cell surface membrane. What accounts for 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.