Protein Mobility in Cell Membranes

Steps:

• Fluorescent dye labels membrane proteins for visualization.
• Laser bleaches fluorescence in a specific membrane area, creating a dark spot.
• Over time, fluorescence returns to the bleached area.
• Return of fluorescence indicates unbleached proteins from adjacent areas diffused into the spot.

Why C is correct:

• In the fluid mosaic model, membrane proteins exhibit lateral diffusion within the phospholipid bilayer, allowing them to move freely and repopulate the bleached region.

Why the others are wrong:

• A: Experiment shows protein movement but not exclusivity to outer surface.
• B: Focus is on lateral movement, not restriction between bilayer layers.
• D: Demonstrates membrane fluidity, not the bilayer structure itself.

Final answer: C