biochemistry quiz on saccharides 10/30/23

aldose vs ketose

Aldose (aldehyde)

Ketose (ketone)

monosaccharide carbon count:

3 or more.

D and L notation

Epimer:

different configuration at a single chiral center

epimer at C-4

D-Glyceraldehyde

aldotriose

D-Erythrose

aldotetrose

D-Ribose

Aldopentose

D-Arabinose

Aldopentose

D-Xylose

aldopentose

D-Glucose

Aldohexose

D-Mannose

Aldohexose

D-Galactose

Aldohexose

dihydroxyacetone

ketotriose

D-Erythrulose

ketotetrose

D-Ribulose

ketopentose

D-Xylulose

ketopentose

D-Fructose

ketohexose

Cyclization naming of aldohexoses:

a-D-Glucopyranose

the aldehyde forms the anomeric carbon! (C1)

cyclization of ketohexose:

B-D-Fructofuranose

C2 becomes the anomeric carbon

B-D-Glucosamine

N-Acetyl-B-D-glucosamine

B-D-Glucuronate

D-Gluconate

anomer

epimer at the hemiacetal/hemiketal carbon

Converting Fischer projection to Haworth perspective:

1. Draw pyranose or furanose ring and # carbons

2. CH2OH pointed up for D isomer

3. OH on left in Fischer is pointed up in Haworth

4. OH on right in Fischer is pointed down in Haworth

5. Assign anomeric carbon

Reducing sugar:

open-chain form with aldehyde group (aldose) or ring form with free hemiacetal group.

Formation of acetal or ketal what kind of bond?

glycosidic bond

Disaccharides are linked by ?

Glycosidic bond, forming an acetal at C1

Naming Disaccharides: Maltose

1. Identify nonreducing and reducing end

2.Name nonreducing sugar ("syl" suffix)

3.Two carbons involved in glycosidic linkage

4.Name reducing sugar ("ose" suffix)

Contains two glucoses

a-D-Glucopyranosyl (1-4) B- D-Glucopyranose

Lactose

Contains Gal and Glc (B-1,4-linkage)

Sucrose

Glucose and Fructose (a,B-(1-2)) linkage

Trehalose

two Glucoses:

a linked

Starch is made up of ?

Amylose and Amylopectin

Amylopectin

Branched

a-D-glucose

a-1, 4-linkages

a-1, 6-linkages (branch points)

every 8-10 glucoses there is a branch point

Amylose:

unbranched

a-D-glucose

a-1,4-linkages

Glycogen

More extensively branched than starch. Basically the same as amylopectin

branches every 5-7 glucoses

significance of branching:

Branching increases the non-reducing ends.

Cellulose

Glucose residues linked by B-1,4-linkages

unbranched

B-D-glucose

B-1,4-linkages

amylose but B linkages

Chitin

N-acetyl-B-D-Glucose

Unbranched

B-1, 4-linkages

Cellulose and chitin make:

sheets/sandwiches

Starch and glycogen form :

helix/tightly coiled helix

What is a GAG?:

Glycosaminoglycans

Uronic acid (carboxyl)

N-acetylglucosamine or N-acetylgalactoseamine (amide)

repeating units...

They are negatively charged

Unbranched

Some contain sulfate esters