Here's why:
* Plants: Cell walls provide structural support and rigidity to plant cells, allowing them to withstand internal pressure from water uptake. They are primarily composed of cellulose.
* Algae: Algae also have cell walls, but their composition varies depending on the species. Some algae have cell walls made of cellulose, while others have walls composed of silica or other polysaccharides.
* Fungi: Fungi have cell walls that are primarily made of chitin, a tough polysaccharide.
* Bacteria: Most bacteria have cell walls made of peptidoglycan, a complex polymer.
While animal cells do not have cell walls, they do have a cell membrane that encloses the cell and regulates what enters and leaves.
