Caption: Phagocytosis
Text: The process of by which a single cell engulfs and ingests particles or other cells to form a phagosome, or food vacuole. The phagosome is a membrane-bound spherical vacuole that forms by pinching off from the cell membrane. The phagosome can fuse with a lysosome, which is another membrane-bound vacuole that contains digestive enzymes, to form a phagolysosome, which digests the engulfed material. The products can be used for energy or synthesis of other compounds, and unused debris can be ejected into the environment by exocytosis, i.e., fusion of the phagolysosome with the plasma membrane in what is essentially a reversal of phagocytosis.