All factories have exterior walls that protect and support them and interior walls that create separate work areas. They usually have some kind of production line where a product is assembled and an executive department that decides what product is made. A finishing department processes and prepares the product for shipping, and a packaging department wraps the product. In addition, a factory has a receiving department that brings in the components it needs to make its product, a communications department that allows it to contact suppliers, and a power plant that provides the energy it needs to run. Finally, a custodial staff keeps everything clean and in good working order.
Cells are very similar to factories.
To stay alive and function properly, cells have a division of labor similar to that found in factories. All eukaryotic cells are composed of a plasma membrane, a nucleus, and cytoplasm. These structures can be compared with a factory's departments. The plasma membrane regulates what enters or leaves the cell. It is analogous to the shipping and receiving department of a factory.