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Chapter 16
16
Carbohydrates
Study Goals
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Identify the common carbohydrates in the diet.
Distinguish between monosaccharides, disaccharides, and polysaccharides.
Identify the chiral carbons in a carbohydrate.
Label the Fischer projection for a monosaccharide as the D- or L-enantiomer.
Write Haworth structures for monosaccharides.
Describe the structural units and bonds in disaccharides and polysaccharides.
Chapter Outline
16.1 Types of Carbohydrates
Explore Your World: Photosynthesis
16.2 Classification of Monosaccharides
16.3 D and L Notations from Fischer Projections
16.4 Structures of Some Important Monosaccharides
Health Note: Hyperglycemia and Hypoglycemia
16.5 Cyclic Structures of Monosaccharides
16.6 Chemical Properties of Monosaccharides
Health Note: Testing for Glucose in Urine
16.7 Disaccharides
Explore Your World: Sugar and Sweeteners
16.8 Polysaccharides
Health Note: How Sweet Is My Sweetener?
Explore Your World: Polysaccharides
Explore Your World: Iodine Test for Starch
Chapter Summary and Demonstrations
1. Monosaccharides, Chiral Molecules, and Fischer Projections
The monosaccharides are classified as aldo- or ketopentoses and aldo- or ketohexoses. The
structures of chiral and achiral molecules are compared. Fischer projections and Haworth structures
for the anomers of the monosaccharides are drawn. The oxidation of saccharides and the formation
of glycosidic bonds is emphasized in types of reactions.
2. Types of Carbohydrates
The major monosaccharides and disaccharides in the diet are discussed along with some medical
problems with utilization of glucose including blood glucose levels in normal, hyper-, and
hypoglycemic conditions are described. The polysaccharides are described along with the type of
bonding between monomer units. Identification tests for carbohydrates complete the chapter.
Demonstration: Types of Carbohydrates I have students compare the nutritional labeling on
breakfast cereal boxes with emphasis on the types of carbohydrates listed. Then discuss the role of
sucroses, complex carbohydrates, and fiber in the diet.
Demonstration: Have students chew on a cracker for 4-5 minutes. Identify the taste of starch in the
cracker. As an enzyme in saliva breaks apart the bonds in the starch, smaller sugars and
monosaccharides form. After a few minutes, ask students how the taste of the cracker changes.
Why?
Carbohydrates
Laboratory Suggestions
Lab 26 Types of Carbohydrates
Students identify the characteristic functional groups of carbohydrates and observe some physical
and chemical properties of some common carbohydrates.
A. Monosaccharides
B. Disaccharides
C. Polysaccharides
Lab 27 Tests for Carbohydrates
Physical and chemical tests are used to distinguish between monosaccharides, disaccharides, and
polysaccharides.
A. Benedict’s Test for Reducing Sugars
B. Seliwanoff’s Test for Ketoses
C. Fermentation Test
D. Iodine Test for Polysaccharides
E. Hydrolysis of Disaccharides and Polysaccharides
F. Testing Foods for Carbohydrates
Laboratory Skills to Demonstrate
Observation of positive results for carbohydrate tests.
Identification of a change from the blue color of Benedict's reagent to various shades of green to
red-orange as a positive test for the oxidation of aldehydes to carboxylic acids.
Preparation of fermentation tubes.
Use of pipets and bulbs.