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47 Homework exercises. 1. Write the formulas for disaccharides of maltose, isomaltoses (α-D‑glu- copyranosyl- (1,6) -α-D‑glucopyranose), lactose, sucrose, cellobiose (β-D‑glu- copyranosyl- (1,4) -β-D‑ glucopyranose), trehalose (α-D‑glucopyranosyl (1,1) -α-D‑glucopyranose). 2. Write the reduction reactions of Cu (OH) 2 , Ag 2 O with maltose and lactose. Is this reduction possible for sucrose and trehalose. What is the reason for the reducing properties of disaccharides? 3. Write fragments of homopolysaccharide formulas: amylose, amylopectin, glycogen, cellulose, pectin substances. Specify the composition and types of chemical bonds. 4. Write a fragment of the dextran formula. What is his medical and biologi- cal role? 5. Write fragments of the formulas of heteropolysaccharides: hyaluronic acid, chondroitin‑6‑sulfate, specify the composition and types of bonds. 6. Write a scheme of the reaction of hydrolysis of starch. 7. Write a scheme of the reaction of formation of trinitrocellulose, cellulose triacetate. Laboratory work. Experiment 1. Absence of a reducing ability in sucrose. Place 1 drop of sucrose and 6 drops of NaOH into the test tube. Add about 2 ml of water and 1 drop of CuSO 4  solution. A transparent blue solution of complex copper with sucrose is formed. Carefully heat the tube over the flame of the alcohol lamp so that only the top of the solution warms up. Heat only to a boil, but do not boil. Is there a discoloration? What do the results of the experiment mean? Experiment2. Restoring ability of lactose. Place 1 drop of lactose solution and 4 drops of NaOH solution in a tube. Add 1 drop of CuSO 4  solution. A blue precipitate of copper (II) hydroxide forms. When shaken, it dissolves, forming a blue solution of the complex salt of copper (II) with lactose. Carefully heat the tube over the flame of the alcohol lamp so that only the top of the solution warms up. Heat to a boil. The upper part changes color to yellow-redin this reaction. The reaction equation (see the analogous reaction with D‑glucose): O OH OH HO CH 2 OH O H O OH OH CH 2 OH H H OH + 2Cu(OH) 2 COOH H CH 2 OH OH OH OH H O CH 2 OH HO OH OH O + Cu 2 O + 2H 2 O