Problem 19 - Objective Biology for NEET

Question

Chitin is present in (a) Exoskeleton of arthropods (b) Cell wall of fungus (c) Setae of earthworm (d) All of these

Step-by-Step Solution

Answer

Chitin is present in the exoskeleton of arthropods and the cell wall of fungus. So, the correct answers are option (a) and (b).

Step 1: Identifying the presence of Chitin in the Exoskeleton of Arthropods

Chitin is the main component in the exoskeleton of arthropods (like insects, spiders, and crustaceans). Chitin provides protection and support for these organisms. Hence, option (a) is true.

Step 2: Identifying the presence of Chitin in the Cell walls of Fungus

Fungi are eukaryotic organisms and their cell walls contain a high amount of chitin. Because of this, the fungal cell walls are rigid and tough. Therefore, option (b) is correct.

Step 3: Identifying the presence of Chitin in the Setae of Earthworm

Setae in earthworms are external bristle-like structures present on the body surface that provides grip for locomotion. Chitin is not a component of the setae of earthworms. Therefore, option (c) is false.

Step 4: Combining the findings

Given the examination of each statement, options (a) and (b) are correct while option (c) is incorrect. Therefore, option (d) 'All of these' is also not correct for the given question.

Key Concepts

Exoskeleton of Arthropods

The exoskeleton of arthropods is essentially a biological armor that provides support and protection for organisms such as insects, spiders, and crustaceans.
Composed primarily of chitin, this sturdy material is akin to a knight’s suit of armor, shielding arthropods from environmental challenges and potential predators.

Chitin is a polysaccharide, a type of long-chain carbohydrate, that offers both flexibility and strength, allowing arthropods to move with agility despite being encased in a hard outer shell. The presence of chitin is pivotal in the molting process, where arthropods shed their exoskeleton to grow a new, larger one as they mature. This process of molting, called ecdysis, is fundamental for growth and development within this group of animals.

Cell Wall of Fungi

Moving onto the realm of fungi, chitin stands out as a critical structural component within the cell walls of these eukaryotic organisms.
Fungi, which include yeasts, molds, and mushrooms, boast cell walls that are distinct from those of plants. While plants primarily use cellulose, fungi employ chitin to provide their walls with rigidity and structural integrity.

This robust framework afforded by chitin contributes to the fungi’s shape and prevents the cell from lysing, or bursting, when water enters the cell. Moreover, the rigidity of chitin facilitates the fungus’s ability to withstand different environmental pressures and can play a role in the pathogenicity of certain fungi when interacting with host organisms.

Setae of Earthworm

The setae of earthworms are small, hair-like structures that protrude from their skin and are composed mainly of strong, fibrous proteins.
These bristle-like structures play a crucial role in locomotion, helping earthworms to anchor themselves and move through the soil. Unlike the exoskeleton of arthropods and the cell wall of fungi, chitin is not a constituent of the earthworm’s setae.

Contrary to the supportive role chitin provides in arthropods and fungi, the earthworm’s setae serve a different function entirely, assisting in mobility and interaction with the earthworm’s environment. Their composition allows for a great deal of flexibility and strength, thus enabling these creatures to burrow effectively and maintain stability within their subterranean habitats.