The cell walls of fungi are made of chitin and other polymers, especially glucans, which are long chains of glucose. Chitin plays the same role in fungal cell walls as cellulose does in plant cell walls. It provides strength, structure and defense to cell contents within.
Fungal cell walls are made up of intertwined fibers. Most of those fibers are long chains of chitin, the same tough compound found in the exoskeletons of animals such as spiders, beetles and lobsters. Although chitin is tough, it is also flexible. The chitin in fungal cells is entangled with glucans and other wall components, such as proteins, forming a mass that protects the cell membrane behind it. The fibrous wall is dynamic and able to reform itself as the fungus grows and changes.