What is the relationship between endocytosis and exocytosis?
They are both types of active transport, requiring the use of energy by the cell, and they are the opposite processes.
Endocytosis is a type of active transport in which a cell takes in a macromolecule, such as a protein or polysaccharide, or a even another cell. In this process, the cell membrane engulfs the substance by pinching inward, forming a vesicle around the substance, which is brought into the cell.
Exocytosis is a type of active transport in which a cell a cell expells a macromolecule, such as a hormone or an enzyme, or cellular waste. In this process the Golgi body packages the molecule into a vacuole, which then fuses with the cell membrane, spilling its contents into the area surrounding the cell.
The following diagram represents endocytosis.
The following diagram represents exocytosis , in which a substance has been packaged within a vesicle by the Golgi body. The plasma membrane of the vesicle then fuses with the cell membrane and its contents are expelled.