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51 mixture until yellow color appears. The tube is cooled under a stream of cold water, and add dropwise a solution of ammonia until orange appears. Write the reaction equation (see the textbook). What amino acids will give a similar reaction? LESSON 24. CHEMISTRY OF PEPTIDES AND PROTEINS Required basic level of knowledge. Structure and properties of amino acids. Mechanisms for the formation of covalent, ionic, hydrogen, van der Waals bonds. Amphotericity. Acidic properties, basic properties. Questions for the preparation for the lesson. 1. Peptides. Definition. Scheme of the formation of a peptide bond by the example of a tripeptide. 2. Proteins. Definition. Classification of proteins. 3. Structures of protein molecules. Definition, stabilizing bonds, scheme. 4. Sequencing. Determination of the primary structure of peptides and proteins by the Edman method. 5. Properties of proteins. • amphotericity: the definition, the cause of amphoteric proteins. • isoelectric point and isoelectric state: the definition, examples, the reason for the difference in the isoelectric points of different proteins. The charge of proteins in different solution media, the recharging of the protein molecule. • Reversible precipitation. Salting out. Definition, salts that cause reversible precipitation. The medical and biological significance of salting out proteins. • Irreversible precipitation. Denaturation. Definition, factors causing denaturation. Protein structures damaged by denaturation. Medico-biological significance of denaturation. • forms of protein molecules, examples of globular and fibrillar proteins. 6. Qualitative reactions to proteins: ninhydrin, biuret, xanthoprotein (for the presence of aromatic amino acids), the Fole reaction (for the presence of sulfur- containing amino acids). Test-control on the topic “Chemistry of amino acids, peptides and proteins” Homework exercises. 1. Write formulas of six tripeptides containing alanine, threonine and tryptophan.