ASMEPPS Science Practice Test 2025 – Comprehensive All-in-One Guide for Exam Success!

Chitin is the correct answer because it is a naturally occurring polymer that provides structural support in the exoskeletons of arthropods, which include insects, arachnids, and crustaceans. It is a nitrogen-containing polysaccharide that is vital for maintaining the rigidity and strength of these organisms' exoskeletons, allowing them to protect their bodies and retain moisture in terrestrial environments.

Chitin is composed of repeating units of N-acetylglucosamine, and its unique structure contributes to the hardness and durability that is essential for arthropods. In addition to its presence in exoskeletons, chitin is also found in the cell walls of fungi, which further emphasizes its importance in biological systems.

Other options represent different polysaccharides or monosaccharides that do not serve the same structural role. Cellulose, for example, is found in plant cell walls and provides structural support there, while starch serves as an energy storage polysaccharide in plants. Glucose, on the other hand, is a simple sugar and a primary energy source for many organisms but does not contribute to exoskeleton formation. Therefore, chitin is distinctly characterized by its role in forming the exoskeletons of arthropods,