Chitin is a nitrogen-containing linear polysaccharide of ß(1->4) linked units of N-acetyl-ß-d-glucosamine. The structure of chitin is similar to cellulose except for the replacement hydroxyl group (-OH) at the carbon 2 with an acetyl amine group (–NH–CO–CH3). Chitin is the main component of the exoskeleton, or outer covering of insects, crustaceans, and arachnids. It is also found in the cell walls of certain fungi and algae. After cellulose, chitin is the second most abundant biopolymer in nature. It is insoluble in water, organic solvents, weak acids and lyes.
Cystine (C6H12N2O4S2) is a dimer of cysteine. It is formed by the oxidation of the thiol groups (-SH) of two cysteines generating a disulphide bridge (-S-S-). Cystine is a white crystalline solid that is slightly soluble in water. Cystine is particularly abundant in skeletal and connective tissues and in hair, horn, and wool.
Dipeptide is an organic compound formed when two amino acids are joined by a peptide bond. Depending on which groups of amino acids are involved in the peptide bond four dipeptides can be formed from two different amino acids. For example, glycine (Gly) and alanine (Ala) can give two symmetrical dipeptides (GlyGly and AlaAla) and two unsymmetrical dipeptides (GlyAla and AlaGly). The naming is done by reading the sequence from the N-terminus to the C-terminus.
Generalic, Eni. "Kovalentna veza." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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