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Where is chitin found in living organisms?

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A biochemical flowchart shows the metabolic pathways for carbohydrate utilization, including glycolysis, the pentose phosphate pathway, and the tricarboxylic acid (TCA) cycle. The diagram traces the conversion of glucose, fructose, and glycerol through various intermediates, leading to energy production, carbon dioxide release, and biosynthesis of amino acids and porphyrins. Key steps and branches are labeled, with colored boxes highlighting biosynthetic outputs.
Carbohydrate Pathways for the utilization of carbohydrates.

Chitin is a structural polysaccharide found in a variety of living organisms, where it serves as a key component for support and protection:

  • Arthropods and other invertebrates: It is the major component of the outer skeletons of insects, crustaceans (such as crabs and lobsters), and other arthropods. It is also found in the internal structures of annelid and nematode worms, mollusks, and coelenterates.12
  • Fungi: Chitin is a primary structural component of the cell walls of most fungi, sometimes comprising nearly 50 percent of the dry weight of certain species.23

Often referred to as "animal cellulose," chitin is chemically similar to cellulose but consists of units of the amino sugar N-acetyl-d-glucosamine.12