Final answer:
Chitin and cellulose both provide structural support due to their chemical bonding; chitin does so for arthropod exoskeletons and fungal cell walls, while cellulose does so for plant cell walls.
Step-by-step explanation:
The chemical bonding in chitin enables it to function similarly to cellulose in providing structural support. Chitin is a long-chain polysaccharide made of repeating units of N-acetyl-β-d-glucosamine, which is a modified sugar with a nitrogen group attached. This structure allows for the formation of strong, protective layers, which are crucial for the exoskeleton of arthropods such as insects and crustaceans, and also for the cell walls of fungi. Just like cellulose, which is a major component of plant cell walls and gives them their rigidity, chitin's long polymer chains bond strongly with each other to form a tough, protective barrier. These chemical bonds are responsible for the hardness and durability of the exoskeleton in arthropods, which protects them similarly to how cellulose protects plant cells.