Carbohydrates
C483 Spring 2013
1. Examine the Fischer projection below. How is this carbohydrate classified?
A) L enantiomer; aldopentose. B) L enantiomer; ketopentose. C) D enantiomer; aldohexose. D) D enantiomer; ketopentose.
2. Which is the proper Haworth projection of β-D-galactopyranose?
3. Which statement is not true about this structure?A. It is a ketoseB. It is a beta anomer.C. It is a furanose.D. It is a pentose.
4. What is the name of the disaccharide shown below that is formed by joining two monomers of D-glucose? A) β-D-glucopyranosyl-(1→4)-β-D-glucopyranose. B) α-D-glucopyranosyl-(1→4)-α-D-glucopyranose. C) β-D-glucofuranosyl-(1→4)-β-D-glucofuranose. D) α-D-glucopyranosyl-(1→3)-β-D-glucopyranose.
Objectives
• Recognize particular carbohydrate structures• Know general structural elements of cyclic
monosaccharides and disaccharides, and their implications for structure/function
• Predict the products of condensation reactions and hydrolysis
Straight-chain Monosaccarides• Aldose/ketose terminology• Triose, tetrose, pentose, hexose• Recognize isomerization (TPI—see page 173)– Should I know the mechanism?
Stereochemistry
• D/L designation• Fisher Projections
Aldose Tree
Ketose Tree
Structures to Know
• D-glucose• D-glyceraldehyde• D-Ribose• D-Galactose• D-fructose• dihydroxyacetone
Cyclic Monosaccharides
• Pyranose• Haworth
Projection• Anomeric carbon• Alpha and beta
anomers
Cyclic Monosaccharides
• Furanose• Just focus on
what is commonly observed– Pyranoses:
glucose, galactose
– Furanoses: ribose, fructose
X
Conformations
• Haworth and chair (no envelopes, etc)
Mutarotase
• Reaction of cyclic carbohydrates which equilibrates anomers
Section 8.4 Sugar Phosphates
Structure of Disaccharides
• Condensation of Monosacharides– Loss of anomeric hydroxyl group and proton of
nucleophilic alcohol– Glycosidic Bond
Structure of Disaccharides
• Nomenclature of linkage– Find the acetal!
• Reducing sugar– Find the hemiacetal!
• “Lactose”– Reducing sugar– Nonreducing sugar– Linkage (number and
stereochemistry)
Polysaccharides
Starch and Glycogen
Cellulose
• Watch structure carefully!
Answers
1. B2. I
3. D4. A
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