What type of diffusion is mediated by a carrier protein?

Facilitated diffusion is a type of passive transport that requires assistance from a carrier protein to help certain molecules cross the cell membrane. In this process, molecules that are not able to easily pass through the lipid bilayer—such as glucose or ions—bind to specific carrier proteins. These proteins undergo a conformational change, allowing the molecules to be transported across the membrane without the use of energy.

This transport occurs along the concentration gradient, meaning that molecules will move from an area of higher concentration to an area of lower concentration until equilibrium is achieved. The involvement of carrier proteins distinguishes facilitated diffusion from simple diffusion, where molecules move freely without assistance. Unlike active transport, which requires energy to move substances against their concentration gradient, facilitated diffusion is energy-independent, as it is driven solely by the concentration gradient. Osmosis specifically refers to the diffusion of water molecules, which doesn't directly involve carrier proteins in the same way.