Exocytosis is the durable process by which a cell directs the contents of secretory vesicles out of the cell membrane.# Endocytosis> Endocytosis is the process by which cells absorb molecules (such as proteins) from outside the cell by engulfing it with their cell membrane. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma membrane or cell membrane. The process opposite to endocytosis is exocytosis.">