What are the primary types of endocytosis?

The main types of endocytosis are phagocytosis, receptor-mediated endocytosis, and pinocytosis. Phagocytosis involves the engulfing of large particles or cells. It allows immune cells such as macrophages to destroy cancer cells, virus-infected cells, bacteria, and other harmful substances. It is also the process in which certain organisms obtain food from their environment. The phagocyte must be able to attach to the target cell and degrade it. Pinocytosis, in contrast to phagocytosis, involves cell drinking. Fluids and dissolved nutrients are taken into a cell by pinocytosis. During the process, vesicles become internalized and particles as well as extracellular fluid are transported inside the cell. Once inside the cell, the vesicle may fuse with a lysosome. The digestive enzymes from the lysosome degrade the vesicle and release its material into the cytoplasm to be used by the cell. In some circumstances, the vesicle doesn’t fuse with a lysosome and travels across the cell to fuse with the membrane on the other side. This is a mechanism in which a cell can recycle cell proteins and lipids. In receptor-mediated endocytosis, the process is utilized by cells for internalization of specific molecules. These molecules bind to receptors on the membrane before they are internalized by endocytosis. Once the specific molecule binds to the receptors, the pit regions are internalized and clathrin-coated vesicles are generated. After fusing with early endosomes, the catherine-coating is removed from vesicles and contents spill into the cell.