What is facilitated diffusion primarily characterized by?

Facilitated diffusion is a passive transport mechanism characterized by the assistance of transport proteins in moving molecules across a cell membrane. This process allows substances that cannot easily pass through the lipid bilayer, such as polar molecules or larger molecules, to enter or exit the cell without the expenditure of energy.

Transport proteins, which can be either channel proteins or carrier proteins, play a crucial role in facilitated diffusion by providing pathways or binding sites that specifically interact with certain molecules, allowing them to move down their concentration gradient. This means that molecules will naturally flow from an area of higher concentration to an area of lower concentration until equilibrium is reached.

This process is essential for maintaining cellular homeostasis and regulating the internal environment of cells. By utilizing transport proteins, facilitated diffusion ensures that vital nutrients can be absorbed efficiently and waste products can be adequately expelled without requiring cellular energy.