Endocytosis in which the cell selects and ingests a particular substance from the surrounding intercellular medium. Particles of molecules destined to enter the cell bind to specific receptors on the cell surface and are then drawn into the cell by the invagination of the cell membrane. The process first forms a coated pit lined with proteins called clathrin; the invaginated pit then detaches to become a coated vesicle inside the cell. [See illustration overleaf.]
Subjects: Genetics and Genomics.