Lecture 8/Ch 7: Monosaccharide and Disaccharides

Aldose vs ketose

stereoisomers

position of one of the molecules in a chiral center is flipped

epimers

a subclass of stereoisomers that differ in the configuration of exactly one chiral center, while all other stereocenters remain identical

because enzymes are SPECIFIC and these sugars therefore enter metabolic pathways and are processes differently

Why do we care about epimers?

enantiomers

mirror images, switched at every chiral center

If intramolecular reactions occur, they make ring structures since sugars have both carbonyl and hydroxyl groups

Hemiacetal/Hemiketal reaction

anomeric carbon

the chiral center in a cyclic sugar created by the intramolecular reaction of a carbonyl group with a hydroxyl group to form a cyclic hemiacetal or hemiketal

anomers

a specific type of diastereomer (and epimer) found in cyclic sugar molecules, differing only in their configuration at the anomeric carbon (alpha vs beta)

alpha

at anomeric carbon when -OH is below the plane of the ring

beta

at anomeric carbon when -OH is above the plane of the ring

pyranose

6-membered ring

furanose

5-membered ring

glucose

fructose

ribose

condensation reaction, hemiacetal/hemiketal + 2nd alcohol

how is a glycosidic bond made?

alpha vs beta glycosidic bond

reducing sugars

carbohydrates that possess a free aldehyde or ketone group, allowing them to act as reducing agents by donating electrons to other molecules, usually when reducing end C1 linearizes

galactose

mannose