What is bulk transport?

• A. Movement of large molecules into and out of the cell through vesicles, and it is active
• B. Simple diffusion of small molecules
• C. Osmosis of water
• D. Facilitated diffusion of ions

Answer: (A)

Bulk transport moves large substances or large amounts across the cell membrane using vesicles, and it requires energy. This process includes endocytosis, where the membrane folds in to form a vesicle that brings material into the cell (such as phagocytosis and pinocytosis), and exocytosis, where vesicles fuse with the membrane to release contents outside the cell. The need for vesicle formation and movement makes bulk transport energy-dependent, unlike passive methods.

This differs from simple diffusion, osmosis, and facilitated diffusion, which move smaller particles or rely on carrier proteins without using vesicles or cellular energy. The vesicle-based mechanism is essential for handling large molecules or bulk amounts that can’t pass through the lipid bilayer on their own.