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| Endocytosis and Exocytosis |
Endocytosis is used by cells to move water, macro molecules, or larger objects, such as cell fragments or even whole cells, from outside a cell to the inside of the cell. Exocytosis is the reverse of endocytosis, that is, the movement of materials from the inside to the outside of the cell. Both types of transport move the materials using membrane-bound vesicles.
Endocytosis
In endocytosis, during which materials are moved into a cell, the cell’s plasma membrane engulfs material and packs it into saclike structures called vesicles. The vesicles then detach from the plasma membrane and move into the cell.
Once the vesicle is in the cytoplasm, it will typically fuse with some other membrane-bound organelle, such as a vacuole or the endoplasmic reticulum, and release its contents into the organelle. There are three types of endocytosis: phagocytosis (transport of actual particles), pinocytosis (transport of water, along with any solutes in the water), and receptor-mediated endocytosis (explained in detail below).