Chapter 20
Carbohydrates
CHEM 2124 – General
Chemistry II
Alfred State College
Professor Bensley
Learning Objectives
 Identify the three major types of carbohydrates
 Recognize the major structural featurs of
carbohydrates
 Draw the cyclic forms of monosaccharides and
classify them as alpha or beta anomers
 Recognize the major structural features of
disaccharides
 Describe the characteristics of cellulose, starch,
and glycogen.
Carbohydrates
I. Introduction
•Polyhydroxy aldehydes or ketones, or compounds
that can be hydrolyzed to them.
A. Monosaccharides
1. Aldoses vs. Ketoses
Carbohydrates
B. Triose vs. Tetrose vs. Pentose vs. Hexose
C. Physical Properties
Carbohydrates
D. Fischer Projection Formulas
E. D vs. L Enantiomers of Monosaccharides
Carbohydrates
F. Common Monosaccharides
1. Glucose
2. Galactose
3. Fructose
Carbohydrates
II. The Cyclic Forms of Monosaccharides
•Review: What is a
hemiacetal?
•Review: How does a
cyclic hemiacetal
form?
Carbohydrates
A. Anomeric Carbon / Anomers
B. How to draw cyclic forms of monosaccharides
(Haworth Projections)
The Cyclic Forms of Monosaccharides
HOW TO Draw a Haworth Projection from an Acyclic
Aldohexose
Example Draw both anomers of D-mannose in a
Haworth projection.
Carbohydrates
III.Disaccharides
A. Introduction
•Monosaccharides linked together through
formation of an acetal:
• Known as a glycosidic bond or glycosidic
linkage
Carbohydrates
•The glycosidic linkage joining the two rings can
be alpha (a) or beta (b).
Carbohydrates
B. Common Disaccharides
1. Lactose
2. Sucrose
Carbohydrates
C. Artificial Sweeteners
1. Aspartame (Equal, Nutra Sweet) = 150 x
sweeter than Sucrose
2. Saccharine (Sweet n’ Low) =
350 x sweeter than Sucrose
Carbohydrates
C. Artificial Sweeteners
3. Sucralose (Spelnda) = 600 x sweeter than
Sucrose
4. Others
Carbohydrates
IV. Polysaccharides
A. Cellulose
B. Starch
1. Amylose
Carbohydrates
2. Amylopectin
C. Glycogen