Cellulose is more common in plants, and it is the material that makes up the Cell wall of plant cells. The main function of a cell wall is to give strength and structure to the cell.
Phospholipids make up the cellular membrane that commonly surrounds animal cells. The purpose of the membrane is to allow certain things to come in and others to leave (selective).
One of the main reasons why there is a need to create additional three kingdoms was due to the invention of the microscope. The scientific device paved way for a more intensive study of the tiny organisms most considered as single-celled which cannot be seen by the naked eye.
