* Prokaryotes are single-celled organisms that lack a nucleus and other membrane-bound organelles. Their cell wall is primarily composed of peptidoglycan, a complex polymer.

* Plant cells are eukaryotic cells that contain a nucleus and other membrane-bound organelles. Their cell wall is primarily composed of cellulose, a complex carbohydrate.

Animal cells do not have a well-defined cell wall. Instead, they have a flexible cell membrane that surrounds the cell.