exocytosis is the durable, energy consuming process by which a cell directs the contents of secretory vesicles out of the cell membrane and into the extra cellular space.these membrane bound vesicles contain soluble proteins to be secreted to the extra cellular environment as well as membrane proteins and lipids that are sent to become components of the cell membrane. However the mechanism of the secretion of intravesiclular contents out of the cell is very different from the incorporation in the cell membrane of ion channels, signaling molecules, or receptors.

In endocytosis, the cell engulfs some of its extracellular fluid including material dissolved or suspended in it. A portion of the plasma membrane is invaginated and pinched off forming a membrane bounded vesicle called an endosome.