How Do Membrane Proteins Move Across the Lipid Bilayer?

💡 The Answer

• Lateral diffusion in the membrane plane is rapid and common.
• Transverse diffusion (flip-flop) is very slow without enzyme assistance.
• Flippases, floppases, and scramblases catalyze phospholipid movement between leaflets.
• For transmembrane proteins, flip-flop is essentially impossible without major conformational changes.