Which is a type of passive movement?

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

Answer: (C)

Passive movement means without using cellular energy, relying on a concentration difference to drive the process. Diffusion is the classic example: particles move from areas of high concentration to areas of lower concentration until they balance out. This can happen directly through the lipid bilayer for small nonpolar molecules or via channels and carriers in the membrane in facilitated diffusion, but the key point is that no metabolic energy is required.

In contrast, exocytosis and endocytosis move materials by forming vesicles that bud from or fuse with the membrane, which requires energy and is considered active transport. Active transport itself moves substances against their gradient, also using energy. So diffusion best fits the idea of passive movement.