Which process describes how large molecules enter or leave the cell?

• A. Diffusion
• B. Endocytosis
• C. Facilitated diffusion
• D. Osmosis

Answer: (B)

Large molecules can’t pass through the lipid bilayer or channels on their own. They require vesicular transport, where the cell membrane folds inward to engulf the material and then buds off to form a vesicle inside the cell. This process, endocytosis, is energy-intensive and specifically handles the uptake of big particles and macromolecules such as proteins or bacteria. In contrast, diffusion and facilitated diffusion deal with smaller molecules (diffusion simply by random motion, and facilitated diffusion with a transport protein, but not macromolecules), and osmosis is about water movement. Since the question concerns large molecules entering (and leaving would be exocytosis, which isn’t listed), endocytosis is the best description for how large molecules enter the cell.