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

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

Answer: (A)

Diffusion is the movement of particles from an area of high concentration to an area of low concentration, driven by random molecular motion and requiring no energy input. This natural spreading continues until the substances are evenly distributed, which is exactly what’s described in the statement. In everyday terms, things like dye in water or a scent spreading through a room illustrate diffusion—the substance moves down its concentration gradient without the cell spending energy.

Osmosis is specifically the diffusion of water across a selectively permeable membrane, not general solute movement. Active transport uses energy to move substances against their gradient, and endocytosis involves the cell membrane folding inward to engulf material, which requires energy.