1. Cyclic monosaccharides

2. Cyclic structure • Most of the time, monosaccharides exist as ring structures formed when a carbonyl group and a hydroxyl group in the SAME molecule react • This results in a ring structure that is more stable

3. Drawing a cyclic glucose • Turn the chain on its side • Fold the chain into a hexagon • Called a Haworth structure • Bond the 1st carbon to a new OH group • If down = alpha / up = beta

4. Cyclic glucose

5. Alpha vs. Beta

6. Chemical properties of monosaccharides • Oxidation of monosaccharides • The aldehyde group of the open chain structure oxidizes easily • This produces a carboxylic group • Monosaccharides that reduce another group (are oxidized) are called reducing sugars

7. Oxidation of glucose

8. disaccharides • Easily hydrolyzed into their two monosaccharides • Maltose + water  glucose + glucose • Lactose + water  glucose + galactose • Sucrose + water  glucose + fructose

9. What links the monosaccharides? • When a hydroxyl group of one monosaccharide reacts with a hydroxyl group of another, a glycosidic bond forms, forming a disaccharide

10. Forming maltose