Chitin: Definition, Structure & Function

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  • 0:01 What Is Chitin?
  • 0:54 Arthropods & Crustaceans
  • 1:55 Chitin & Human Uses
  • 3:02 Lesson Summary
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Lesson Transcript
Instructor: Terry Dunn

Terry has a master's degree in environmental communications and has taught in a variety of settings.

Although you may have never heard of it, chitin is abundant in nature. It's also become very useful to people. What is chitin? What animals have chitin? How do people use chitin? Find the answers here.

What Is Chitin?

'Faster than a speeding bullet, more powerful than a locomotive, able to leap tall buildings in a single bound.' Okay, maybe chitin doesn't have Superman's powers, but it's still pretty amazing stuff. Think of it as nature's plastic. Depending on what it's mixed with, it can be hard, pliable, colorful, clear, heavy, or lightweight. It's also one of the most common, carbon-containing items on Earth. Chances are, you are sitting close to some chitin right now.

Chitin is the main ingredient in the exoskeletons of arthropods and crustaceans and is also in the cell walls of fungi. That means everything from beetles, spiders, and butterflies to lobsters, crabs, and shrimp have some chitin in their protective armors. To get technical, chitin is a polysaccharide, make up of N-acetylglucosamine, which is similar to the structure of cellulose in plants.

Arthropods and Crustaceans

Alone, chitin is translucent and not extremely hard, but in the exoskeletons of arthropods, it's intermixed with protein and pigments to form different degrees of hardness and a lot of different colors. For example, a caterpillar or butterfly doesn't have as much chitin in their exoskeletons as a beetle or praying mantis might. The amount of chitin in different arthropods' exoskeletons can be anywhere from 30% to 50%. In crustaceans, chitin is mixed with calcium carbonate to form their sturdy exteriors.

Chitin is secreted by epidermal cells, but once an exoskeleton is formed, it can't grow as the creature inside grows. To get around that problem, most arthropods shed their exoskeletons and start fresh by slowly excreting a new exoskeleton. For a little while, the new one is soft, making the creature more vulnerable to predators. To expand the new exoskeleton, the animal pumps itself up with water or air before the exoskeleton hardens.

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