Question

The chitinous exoskeleton of arthropods is formed by polymerisation of
A. Keratin sulphate and chondroitin sulphate
B. D-glucosamine
C. N-acetyl glucosamine
D. Lipoglycans

Answer 1

Hint: Polymerization is a process in which monomer units join together to form large molecules, called a polymer. Chitin is a nitrogen-containing polysaccharide that consists of the outer covering or exoskeleton of crustaceans, insects and arachnids.

Complete answer:
Chitin is a type of polysaccharides. It is a long chain synthesised from monomeric units of N-acetyl glucosamine. Chitin is found in the cell wall of many fungi, skeleton material of molluscs, annelids and arthropods. Chitin which is present in the exoskeleton is a modified form of it. When it is mixed with calcium carbonate it forms more hard and tough shells of the insects.
Therefore option C is correct because chitin is a polymer unit which is made up of a monomeric unit of N-acetyl glucosamine by process of the polymerisation reaction. Polymerisation means the formation of polymers from monomer units.

Other components like Keratin sulphate and chondroitin sulphate, D-glucosamine, and Lipoglycans are not present in the synthesis of chitin. Therefore other options are incorrect.

Additional information: There are two types of skeleton systems that are endoskeleton and exoskeleton. The endoskeleton system means which is present inside the body in contrast exoskeleton is present outside the body. Their function is to protect and give support to the soft body organs. Endoskeleton can be seen in human and other vertebrates whereas an exoskeleton is mainly found in arthropods. Endoskeleton is made up of hard bones and cartilage. Chitin and calcium carbonate formed the exoskeleton system.

Note: Arthropods are the largest phylum of Animalia group. In this phylum, all the insects are included. Approximately 75% of the animals on the planet are composed of arthropods. They play a major role in an ecosystem. They work as scavengers, helping in recycling of nutrients; they can be the food of other animals and also as pollinators.