Which glycan provides structural support in the exoskeleton of arthropods?

The question asks which glycan provides structural support in the exoskeleton of arthropods.

• Step 1: Recall the composition of arthropod exoskeletons. The exoskeleton of arthropods (insects, crustaceans, arachnids) is a tough, protective outer layer. Its primary structural component is a polysaccharide.

• Step 2: Evaluate the given options.

  • A. Mannose: This is a monosaccharide (simple sugar), not a complex structural polymer.
  • B. Chitin: This is a long-chain polymer of N-acetylglucosamine, a derivative of glucose. It is known to be the main component of the cell walls of fungi and the exoskeletons of arthropods.
  • C. Glycogen: This is a polysaccharide used for energy storage in animals, primarily in the liver and muscles.
  • D. Starch: This is a polysaccharide used for energy storage in plants.

• Step 3: Identify the correct glycan. Based on the biological roles of these glycans, chitin is the specific polysaccharide that provides structural support in the exoskeleton of arthropods.

The final answer is $\boxed{\text{B}}$