Carbohydrates are classified as monosaccharides (simple sugars), disaccharides (two monosaccharide units), or polysaccharides (many monosaccharide units). Monosaccharides are polyhydroxy aldehydes (aldoses) or ketones (ketoses). Monosaccharides are also classified by their number of carbon atoms: triose, tetrose, pentose, or hexose. 15.2 Fischer Projections of Monosaccharides LEARNING GOAL Identify and draw the D and L configurations of the Fischer projections for common monosaccharides. In a D enantiomer, the —OH—OH group is on the right of the chiral carbon farthest from the carbonyl group; the —OH—OH group is on the left in the L enantiomer. Important monosaccharides are the aldohexoses, glucose and galactose, and the ketohexose, fructose. 15.3 Haworth Structures of Monosaccharides LEARNING GOAL Draw and identify the Haworth structures for monosaccharides.
The predominant form of a monosaccharide is a ring of five or six atoms. The cyclic structure forms when an —OH—OH group (usually the one on carbon 5 in hexoses) reacts with the carbonyl group of the same molecule. The formation of a new hydroxyl group on carbon 1 gives α and β anomers of the cyclic monosaccharide. 15.4 Chemical Properties of Monosaccharides LEARNING GOAL Identify the products of oxidation or reduction of monosaccharides; determine whether a carbohydrate is a reducing sugar. The aldehyde group in an aldose can be oxidized to a carboxylic acid, while the carbonyl group in an aldose or a ketose can be reduced to give a hydroxyl group. Monosaccharides that are reducing sugars have an aldehyde group in the open chain that can be oxidized. 15.5 Disaccharides LEARNING GOAL Describe the monosaccharide units and linkages in disaccharides. Disaccharides are two monosaccharide units joined together by a glycosidic bond. In the common disaccharides maltose, lactose, and sucrose, there is at least one glucose unit. Maltose and lactose form α and β anomers, which makes them reducing sugars. Sucrose does not have α and β anomers and is not a reducing sugar. 15.6 Polysaccharides LEARNING GOAL Describe the structural features of amylose, amylopectin, glycogen, and cellulose. Polysaccharides are polymers of monosaccharide units.
Amylose is an unbranched chain of glucose with α(1→4)α(1→4) - glycosidic bonds, and amylopectin is a branched polymer of glucose with α(1→4)α(1→4) - and α(1→6)α(1→6) -glycosidic bonds. Glycogen is similar to amylopectin with more branching. Cellulose is also a polymer of glucose, but in cellulose, the glycosidic bonds are β(1→4)β(1→4) -bonds. Chapter Review 16.1 Carboxylic Acids LEARNING GOAL Write the IUPAC and common names for carboxylic acids and draw their condensed and line-angle structural formulas. A carboxylic acid contains the carboxyl functional group, which is a hydroxyl group connected to a carbonyl group.
You've reached the end of your free preview.
Want to read all 32 pages?
- Fall '08
- DNA, Carboxylic acid