Endocytosis is the uptake of extracellular macromolecules   across the plasma membrane into the cell. The objects to be ingested is progressively  enclosed by a  small  portion  of  the  plasma  membrane that  first  invigilates   and  then pinches off to form an intracellular  vesicle having  the ingested  macromolecule. Endocytosis can be divided into three distinct parts depending  on the size of the ingested  macromolecule  and whether  particular  cell surface  receptors  are included. These 3 procedures are receptormediated, endocytosis pinocytosis, and phagocytosis.