What process describes the movement of particles from high to low concentration?

The movement of particles from an area of high concentration to an area of low concentration is known as diffusion. This process occurs spontaneously as particles tend to spread out evenly in a given space. Diffusion does not require energy; it relies on the natural kinetic energy of the particles, which allows them to move and interact with one another.

In biological systems, diffusion plays a critical role in various functions, such as the exchange of gases in the lungs, where oxygen diffuses into the blood and carbon dioxide diffuses out, as well as the movement of nutrients into and waste products out of cells.

Osmosis is a specific type of diffusion that pertains to the movement of water molecules across a semi-permeable membrane, while active transport involves the movement of particles against their concentration gradient, which requires energy. Facilitated diffusion, on the other hand, is a type of diffusion that uses membrane proteins to help transport substances that may not easily cross the lipid bilayer.