Question

Why is the polysaccharide chitin a suitable material for the exoskeleton of invertebrates such as lobsters? What other sort of material can play a similar role?

Short answer

Chitin is strong, lightweight, and flexible, making it ideal for invertebrate exoskeletons. Calcium carbonate in mollusk shells serves a similar role.

Step-by-step solution

- Understanding Chitin

Chitin is a long-chain polymer of N-acetylglucosamine, a derivative of glucose. It is a primary component in the exoskeleton of arthropods and provides structural support and protection.

- Properties of Chitin

Chitin is strong, lightweight, and flexible. These properties make it an ideal material for forming the exoskeleton of invertebrates, which need a protective outer shell that does not impede movement.

- Why Chitin is Suitable for Exoskeletons

The high tensile strength and durability of chitin make it suitable for withstanding physical stresses while providing armor-like protection. Additionally, chitin can be easily remodeled and repaired by the organism.

- Alternative Materials

Another material that can play a similar role is calcium carbonate, which is used by mollusks to form their shells. It provides a rigid and protective covering, although it is less flexible compared to chitin.

Key concepts

N-acetylglucosamine Polymer

N-acetylglucosamine is a derivative of glucose. When many units of N-acetylglucosamine join together, they form a long-chain compound known as chitin. Chitin is essential for many organisms, especially arthropods.
It is a tough, flexible material that is both lightweight and strong. This makes it perfect for creating protective structures like exoskeletons. Additionally, because it is a polymer, chitin can easily be remodeled, allowing for growth and repair throughout the arthropod's life.

• Long-chain polymer formed by N-acetylglucosamine
• Essential compound for arthropod exoskeletons
• Flexible, strong, and lightweight

In conclusion, chitin's unique properties make it indispensable for the structural needs of various organisms.

Arthropod Structural Support

Arthropods, such as lobsters and insects, require a sturdy structure for support and protection. This structure is known as the exoskeleton. Made primarily of chitin, these exoskeletons are perfectly suited to their needs.
The exoskeleton serves multiple purposes:

• Protection from predators and external injuries
• Prevents dehydration by retaining moisture
• Provides a framework for muscle attachment, allowing for movement

Given its flexibility, the chitin exoskeleton does not hinder the arthropod's mobility. Moreover, it can be repaired and remodeled to accommodate growth. Therefore, an exoskeleton solves many of the challenges faced by arthropods.

Calcium Carbonate Alternative

Apart from chitin, another material that provides structural support in nature is calcium carbonate. This compound is especially prevalent in the shells of mollusks.
Calcium carbonate offers several advantages:

• Highly rigid, providing strong protection
• Effective barrier against physical impacts and environmental factors

However, there are also downsides to calcium carbonate:

• Less flexible compared to chitin, meaning it can break more easily
• Heavier, which can limit movement and growth

Hence, while calcium carbonate is effective for static protection, it is less suitable for organisms that require greater flexibility and mobility. Understanding these materials better helps in appreciating how different organisms have evolved with materials optimized for their environmental niches.