The movement of molecules from an area of high concentration to an area of low concentration is called?

• A. Osmosis
• B. Diffusion
• C. Active transport
• D. Endocytosis

Answer: (B)

Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration, driven by their natural, random motion. As molecules constantly jiggle, they spread out and spread down the concentration gradient until the substances are evenly distributed. This is a passive process, meaning no energy input is required.

For example, a drop of dye in water or the scent of perfume spreading through a room happen because particles move from where they are crowded to where they are less crowded. Other terms describe different transport routes: osmosis is specifically the diffusion of water across a semipermeable membrane; active transport uses energy to move substances against their gradient; endocytosis involves the cell membrane wrapping around material to bring it inside.