Exocytosis is best described as which of the following?

• A. Endocytosis
• B. A Form Of Active Transport Where Substances Leave The Cell (Digestive Enzymes, Etc)
• C. Is Passive Transport Through Channels
• D. Occurs Only In Plant Cells

Answer: (B)

Exocytosis is a process of bulk transport in which secretory vesicles inside the cell fuse with the plasma membrane and release their contents to the exterior. This is an energy-driven, active transport mechanism because the vesicles must be moved, tethered, and fused by proteins, consuming cellular energy. The example of releasing digestive enzymes illustrates how materials packaged in vesicles are exported out of the cell.

It isn’t endocytosis, which would bring substances into the cell by forming vesicles from the membrane. It isn’t passive transport through channels, since exocytosis moves vesicle contents out rather than relying on diffusion through membrane channels. And it isn’t limited to plant cells; many cell types, including animal cells and plant cells, use exocytosis to secrete substances.