What is the relationship between endocytosis and exocytosis?

They are both types of , 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 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.