Final answer:
Chitin is the polysaccharide found in the cell wall of fungi, composed of N-acetylglucosamine units, and provides structural support.
Step-by-step explanation:
The polysaccharide usually found in the cell wall of fungi is chitin. Chitin is a polymer made up of N-acetylglucosamine subunits, which are hexoses with nitrogen attached. It not only forms the exoskeleton of arthropods, including crustaceans and insects but is also a major structural component of the cell walls in fungi. This contrasts with the polysaccharide cellulose, which is the main component of plant cell walls and is composed of glucose monomers. Although both chitin and cellulose provide structural support, they are composed of different types of monomers and are found in different organisms.