If a cell is found to have a certain function, it can also reflect what structure the cell should have and the characteristics of that structure.

For example, if plasma cells can secrete large amounts of antibodies, it can be assumed that the organelles related to protein secretion in plasma cells, such as ribosomes, endoplasmic reticulum, Golgi apparatus and other structures are more developed than those in other normal cells, but it can not be assumed that the cell does not have a function without a certain structure.

Because prokaryotic cells have a simple structure, do not have a well-developed biofilm system, and do not have a wide variety of organelles, but prokaryotic cells contain chemicals that are related to a specific function, and so they show that even if they don't have a specific structure, they still have a relevant function.

For example, E. coli does not contain an endoplasmic reticulum or a Golgi apparatus, but it can still process proteins because its cytoplasmic matrix contains enzymes needed to process proteins.