* Plant cells: This is the most well-known example. Plant cell walls are primarily made of cellulose and provide structural support, helping the plant to maintain its shape and stand upright.
* Fungal cells: Fungal cell walls are composed of chitin, a strong, flexible polysaccharide. This provides structural support and helps the fungi to absorb nutrients from their environment.
* Bacterial cells: Bacterial cell walls are made up of peptidoglycan, a unique molecule found only in bacteria. This provides protection and helps the cell maintain its shape.
* Archaeal cells: Some archaea have cell walls, but the composition varies depending on the specific type of archaea.
Animal cells do not have cell walls. Instead, they have a cell membrane that provides structural support and regulates what enters and exits the cell.
