Phagocytosis is the ingestion of huge particles like as bacteria and cell debris by large endocytic vesicles called as phagosomes. In order to be ingested the particle must first bind to the surface of the phagocyte, normally by specialized cell surface receptors. Once it is bound to the receptors, the phagocyte is stimulated to start engulfing the particle with its plasma membrane, therefore enclosing it within a phagosome given in the figure. The phagosome then fuses with a lysosome and the ingested particle is broken down. The Utilizable material will be elated into the cytosol, although indigestible substances will stay in the lysosomes building residual bodies. In protozoa, phagocytosis is a form of feeding whereas the ingested material is broken down in the lysosomes and utilized as food.