Which type of diffusion involves the movement of particles from high concentration to low concentration?

The correct answer highlights passive diffusion as the process by which particles naturally move from an area of high concentration to an area of low concentration without the need for additional energy. This movement occurs because particles are constantly in motion, and they tend to spread out evenly in a given space.

In passive diffusion, substances such as oxygen and carbon dioxide can easily cross cell membranes due to their small size and nonpolar characteristics. This movement continues until equilibrium is reached, which is a central concept in cellular processes and homeostasis.

Facilitated diffusion involves the use of transport proteins to help specific molecules cross the membrane, but it is still considered a form of passive diffusion since it does not require energy. Simple diffusion refers to the direct movement of molecules across the membrane without assistance, which is also a type of passive diffusion. Active transport, on the other hand, requires energy to move substances against their concentration gradient, from low concentration to high concentration, and is therefore not relevant to the question of movement from high to low concentration.