Carbohydrates Flashcards
How to determine stereochemistry of sugar?
In Fischer projection,
D = the highest numbered chiral carbon has OH on the right
L = the highest numbered chiral carbon has OH on the left
Define epimer
Diastereomers differing at only one chiral center
6 carbon sugar ring
Pyranose
5 carbon sugar ring
Furanose
Define anomeric carbon
The new chiral carbon formed when sugar forms ring (C1)
Define anomer
Cyclic stereoisomers that differ about the new chiral carbon
Define alpha anomer
Anomeric carbon has OH trans to CH2OH
Define mutarotation
In H2O, cyclic sugars open and reform. α and β variants upon reformation.
Define aldose and ketose
Aldose is aldehyde sugar, ketose is ketone sugar
Define aldonic acid
Carboxylic acid form of aldose
Define reducing sugar
Aldoses, because they can be oxidized to aldonic acids
What is a glycosidic linkage?
An acetal formed by reacting a cyclic sugar (hemiacetal) with an alcohol under acidic conditions
How do cellulose, starch, and glycogen differ?
Orientation of glycosidic bond between glucose monomers.
Cellulose: 1,4-β
Starch and glycogen: Mostly 1,4-α and some 1,6-α (glycogen has more and is thus more branched)
Orientation conversion between Fischer projection and Hawthorn projection
Right side groups point down
Orientation of hydroxyls in D-glucose
D
L
D
D
