Endocytosis is best described as which kind of transport?

• A. Osmosis
• B. Active transport that requires vesicle formation
• C. Facilitated diffusion via channels
• D. Passive diffusion through a pore

Answer: (B)

Endocytosis is a vesicle-mediated, energy-dependent process that brings substances into the cell. The plasma membrane folds inward to engulf the material and then pinches off to form a vesicle inside the cytoplasm, a step powered by cellular energy and remodeling proteins. Because it requires energy and vesicle formation, it is a form of active transport rather than a passive process. It’s not osmosis, which is the movement of water; nor is it facilitated diffusion through channels or simple diffusion through a pore, all of which occur without vesicle formation or energy use.