Endocytosis is the internalisation of extracellular materials, from large macromolecules to fluid and solutes, found at the cell surface. These materials become surrounded by a part of the plasma membrane that invaginates and pinches off to form an endocytic vesicle. Endocytosis can fall under two categories according to the size of vesicles formed. If the vesicles are very small, about 100 nanommetres in diamer, we refer to endocytosis as PINOCYTOSIS. Consequently if vesicles are larger, over 200 nanometres, endocytosis is now referred to as PHAGOCYTOSIS.
The most common route of entry into a cell is via CLATHRIN COATED PITS. Both the LDL receptor and the Transferrin receptor are internalised this way.
There are three fates which internalised material can undergo - DEGRADATION, RECYCLING, TRANSCYTOSIS
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