Which diagram is used to illustrate diffusion?

• A. Plant cell diagram
• B. Animal cell diagram
• C. Diffusion diagram
• D. Bulk transport diagram

Answer: (C)

Diffusion is the passive spreading of particles from a region of higher concentration to a region of lower concentration due to random motion. A diffusion diagram typically shows particles clustered on one side with arrows indicating movement toward less concentrated areas, and it often highlights movement across a membrane without implying energy input. The main idea is movement down the concentration gradient, not requiring vesicles or cellular energy. A plant cell or animal cell diagram focuses on cell structure rather than illustrating the specific process of diffusion, and a bulk transport diagram would depict energy-requiring processes like endocytosis or exocytosis. So the diagram labeled to show diffusion best communicates this concept.