The Cell Wall
Plant cell walls are made of cellulose fibres in a matrics of other polysaccharides. Fungi are an exception,their walls contain chitin.
Bacterial walls are more complex. They contain amino acids and polysaccharides.Cell walls are permeable to gases water and certain solutuions. They have a mechanical function, allowing the cell to become turgid by osmosis, but preventing bursting.
This contributes to the support of the herbaceous plants. Plant cell walls can be strengthened for extra support by the addition of extra cellulose. Plant cell walls are an important route for movement of water and mineral salts.
A primary wall,as in cell division in plants, is laid down on the middle lamella of the cell plate as a loose mesh of cellulose fibres. This gives an elastic structure that allows cell expansion during growth.