What does facilitated diffusion require for the movement of substances?

Facilitated diffusion is a process that allows specific molecules to cross biological membranes with the aid of transmembrane integral proteins, also known as carrier proteins or channels. This mechanism is essential for the movement of substances that are unable to easily pass through the lipid bilayer of cell membranes due to their size, polarity, or charge.

Transmembrane integral proteins assist in this process by providing a pathway for these molecules, enabling them to move down their concentration gradient without requiring energy input. The movement occurs passively, meaning that it does not require ATP hydrolysis, which would be needed for active transport processes.

In contrast to magnetic fields or osmotic pressure, which are not involved in the mechanism of facilitated diffusion, the presence of these integral proteins is crucial for this transport process, making them key to understanding how cells regulate the intake of essential substances like glucose or ions.