Which of the following processes involves the engulfing of large particles by a cell?

Phagocytosis is a specific type of endocytosis that refers to the process where a cell engulfs large particles, including debris, pathogens, or other cells. During phagocytosis, the cell membrane extends around the particle and eventually envelops it to form a vesicle called a phagosome. This phagosome can then fuse with lysosomes to digest the engulfed material, making it an important mechanism for immune response and cellular cleanup.

In contrast, exocytosis involves the expulsion of materials from the cell, usually in the form of vesicles merging with the cell membrane to release their contents outside the cell. Pinocytosis refers to the ingestion of small particles or fluids, where the cell membrane invaginates to form small vesicles containing those liquids or solutes, typically rather than larger solid particles. Passive transport is the movement of substances across cell membranes without the need for energy input, typically involving small ions or molecules moving down their concentration gradient, and is not a process of engulfing particles.

Understanding these distinctions clarifies why phagocytosis is the correct answer—it directly relates to the engulfing of large particles by cells, highlighting its role in cellular ingestion and immune defense.