Chitin Definition, Examples, Function, and Structure

Chitin Definition

Chitin is a large, structural polysaccharide composed of chains of modified glucose. Chitin is found in the exoskeleton of pests, the fungal cell wall and invertebrates, and some hard structures in fish. In terms of abundance, chitin is second only to cellulose. In the biosphere, more than 1 billion tons of chitin are synthesized each year by organisms. This highly versatile molecule can form a solid structure on its own in the form of insect feathers, or even combine with other components such as calcium carbonate to form a clam-like shell.

Like cellulose, no vertebrate animals can digest chitin on their own. Insect-eating animals often contain symbiotic bacteria and protozoa that can break down fibrous chitin into glucose molecules that make it up. However, because chitin is a biodegradable molecule that dissolves over time, it is used in many industrial applications, such as surgical thread and dyes for dyes and glues.

Chitin Definition, Examples, Function, and Structure

Function of Chitin

Chitin, It is like cellulose and keratin, is a structural polymer. Made of smaller monomers, or monosaccharides, structural polymers form strong fibers. When they are secreted into or out of cells in an organized way, the fibers form weak bonds with each other. This adds strength to the entire structure. Chitin and cellulose are made from glucose monomers, while keratin is a fibrous protein. The various structural polymers emerged early in the evolution of life because they are only seen in certain groups. Cellulose is exclusive to plants, keratin from animals, and chitin from arthropods, mollusks, and fungi. Chitin and cellulose evolved early in life history, while keratin emerged in certain animals long after plants and fungi separated from the other eukaryotes.

Structure of Chitin

Chitin is made of modified glucose monosaccharide. Glucose is present as a ring of carbon and oxygen molecules. The bonds between glucose molecules are known as glycosidic bonds. Oxygen generally forming hydroxyl groups bonded to the carbon ring can form a bond with another carbon instead of hydrogen. In this way, monosaccharides can be joined together in long chains. Chitin is formed by a series of glycosidic bonds between substituted glucose molecules.

Chitin Definition, Examples, Function, and Structure

Chitin differs from cellulose due to its replacement on the glucose molecule. Instead of the hydroxyl group (OH), glucose molecules in chitin have an amyl group attached to them that contains carbon and nitrogen. Nitrogen is an electrically positive molecule, while oxygen bonded to the group is electrically negative. This creates a dipole in the molecule, which increases the hydrogen bond formed between these molecules and the molecules around them. When combined in a matrix with various compounds and other chitin molecules, the resulting structure can be very difficult because of all the weak interactions between the surrounding molecules.

Examples of Chitin

Chitin in Arthropods

The arthropod is one of the most diverse groups of animals in the world. Arthropods are invertebrate animals with a body segment plan and a hard exoskeleton composed of chitin and various proteins. The combination of a protected body scheme present in variable segments is highly successful in many different ecosystems.

Arthropods are present everywhere, from the bottom of the ocean to the highest living organisms. Arthropods also vary in size from microscopic mites that live at the base of the hair to giant crabs and insects that can be meters long. The exoskeleton of all these creatures contains structural proteins as well as chitin deposits. Mixed with various proteins, chitin also forms feathers of many insects as a more flexible material. The adaptability of chitin to adapt to these various forms has allowed arthropods to grow into millions of different forms.

Chitin in Fungi

In fungi, chitin is used to form the cell wall. Like cellulose in plants, chitin is additionally deposited with proteins and other molecules. It forms a rigid cell wall between cells, which helps organisms to maintain their shape. Like plant cells, water can be retained in cells to create water pressure against the cell wall. This is known as turgor pressure and increases the strength of each cell. Fungi are able to grow through multiple layers of leaf litter, which can weigh several pounds. It comes from the strength of chitin as a structural fiber.

Chitin Definition, Examples, Function, and Structure

Chitin in mollusks

Choline is seen in a series of other forms in mollusks. Chitin is used in both lower mollusks and more derived cephalopods. In mollusks such as snails, chitin is a part of the radula, an organ that resembles a pointed tongue. Mollusks use the radula to scrape algae and other foods. Cephalopods also use chitin, but to make a beak that can be used to cut through the hard shells of their prey items. Ironically, most prey items are arthropods, and their shells are also made from chitin.

Chitin Definition, Examples, Function, and Structure

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Chitin Definition, Examples, Function, and Structure

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