Final answer:
The three types of endocytosis are phagocytosis, pinocytosis, and receptor-mediated endocytosis, all of which are different methods that cells use to internalize various substances. Exocytosis is the process of expelling materials from the cell.
Step-by-step explanation:
The three types of endocytosis, which are processes used to bring substances into the cell, are: phagocytosis, pinocytosis, and receptor-mediated endocytosis. In phagocytosis, the cell engulfs large particles like bacteria by extending its membrane around the particle and forming a vesicle. Pinocytosis involves the cell taking in small droplets of extracellular fluid along with any dissolved substances. Lastly, receptor-mediated endocytosis is a selective process where specific molecules called ligands bind to receptors on the cell surface which initiates the formation of a vesicle to internalize the ligand-receptor complex. Exocytosis is the reverse process where cells expel large molecules from vesicles that merge with the plasma membrane.