Facilitated diffusion is a kind of diffusion wherein there is passive transport(cannot transport via self) of molecules spontaneously across a biological membrane with the help of the protein molecules of the membrane which act as the carriers for the polar molecules in this diffusion process. In this process, the membrane carrier proteins get bounded to the specific solute to be transported and undergo a series of conformational changes (macromolecular shape change) to transfer the solute across the membrane.