Diffusion characterizes the behavior of both solute and solvent particles in some models simulating the transport properties of biological membranes. (See Diffusion, Osmosis and Nernst Potentials to review these phenomena.)
Given the fluid nature of biological membranes, we might reasonably expect membrane lipid and protein components to be moble as well. And we might equally well predict these components could diffuse laterally within the plane of the membrane. (But not be able to cross or "flip-flop" from one side of the bilayer to the other...why?) Can membrane fluidity be measured? How might the movement of membrane components be studied? To answer these questions, you may first want to investigate or review the structural basis of membrane fluidity, following the thread of topics concerned with Membrane Structure.
In this simulation and those following, imagine the small red particles are lipids and the blue are embedded or integral membrane proteins. When you have finished studying the simulation, move on to the next page to explore an experimental approach to these problems.