Facilitated diffusion is a process that allows substances to cross cell membranes with the help of specific proteins. Unlike simple diffusion, which occurs directly through the lipid bilayer, facilitated diffusion uses channel or carrier proteins to transport molecules like glucose and ions across the membrane. This process does not require energy, as it moves substances down their concentration gradient. This method is essential for cells to maintain homeostasis and acquire necessary nutrients. For example, aquaporins are specialized proteins that facilitate the movement of water, while ion channels help regulate the flow of charged particles. Overall, facilitated diffusion is crucial for cellular function and communication.