EnDcytosis
the taking in of matter by a living cell by invagination of its membrane to form a vacuole.Endocytosis is a form of active transport in which a cell transports molecules (such as proteins) into the cell by engulfing them in an energy-using process. Endocytosis and its counterpart, exocytosis, are used by all cells because most chemical substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane by passive means. Endocytosis includes pinocytosis (cell drinking) and phagocytosis (cell eating).Endocytosis pathways can be subdivided into four categories: namely, receptor-mediated endocytosis, caveolae, macropinocytosis, and phagocytosis.Clathrin-mediated endocytosis is mediated by the production of small (approx. 100 nm in diameter) vesicles that have a morphologically characteristic coat made up of the cytosolic protein clathrin.Caveolae are the most common reported non-clathrin-coated plasma membrane buds, which exist on the surface of many, but not all cell types. Macropinocytosis, which usually occurs from highly ruffled regions of the plasma membrane, is the invagination of the cell membrane to form a pocket, which then pinches off into the cell to form a vesicle (0.5–5 µm in diameter) filled with a large volume of extracellular fluid and molecules within it (equivalent to ~100 CCVs). Phagocytosis is the process by which cells bind and internalize particulate matter larger than around 0.75 µm in diameter, such as small-sized dust particles, cell debris, micro-organisms and apoptotic cells.