ENDOCYTOSIS

ENDOCYTOSIS >>> is a process whereby cells absorb material (molecules such as proteins) from the outside by engulfing it with their cell membrane. It is used by all cells of the body because most substances important to them are polar and consist of big molecules, and thus cannot pass through the hydrophobic plasma membrane. The function of endocytosis is the opposite of exocytosis TYPES OF ENDOCYTOSIS 1. Phagocytosis- (literally, cell-eating) the process by which cells ingest large objects, such as cells which have undergone apoptosis, bacteria, or viruses. The membrane folds around the object, and the object is sealed off into a large vacuole known as a phagosome 2. Pinocytosis- (literally, cell-drinking) is a synonym for endocytosis. This process is concerned with the uptake of solutes and single molecules such as proteins. 3. Receptor- mediated endocytosis is a more specific active event where the cytoplasm membrane folds inward to form coated pits. These inward budding vesicles bud to form cytoplasmic vesicles.