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