What distinguishes exocytosis from endocytosis?

Exocytosis is characterized by the process of releasing substances from a cell. This occurs when vesicles containing proteins, hormones, or other materials fuse with the cell membrane, allowing their contents to be expelled outside the cell. This mechanism is crucial for the secretion of products that are essential for various cellular functions and communication between cells.

On the other hand, endocytosis involves the process in which substances are internalized into the cell. This can occur through engulfing large particles or fluids, a process that allows the cell to take in nutrients or other necessary materials from its environment.

This distinction clearly sets apart exocytosis and endocytosis based on their direction of transport: exocytosis is about moving materials out of the cell, while endocytosis focuses on bringing materials into the cell. Other options do not accurately reflect the functions and characteristics of these processes, such as confusing the types of cells involved or incorrectly categorizing the processes as passive or active.