Biochemistry carbohydrates revision

Epimers

sugars that differ in stereochemistry of one of the carbons other than anomeric carbon (C1 in aldo, C2 in keto) or chiral carbon furthest from anomeric carbon (C5 in hexose sugars)

anomer

sugars that diff in the axial and equatorial groups on their carbons

enantiomer 

all chiral centres have a diff config

aldo sugars

sugars with aldehyde functional group at the end of their chain

keto sugars

sugars with ketone group as part of chain

DL isomerism

Different configurations of a chiral molecule

• D (dextrorotatory - spins polarised light clockwise) - hydroxyl group on penultimate carbon (C5 on hexose sugar) is on the right of the carbon

• L (levorotatory - spins p light anticlockwise) - hydroxyl group on penultimate carbon (C5 on hexose sugar) is on the left of the carbon

Sugar (saccharide) chemical origination 

Are aldehyde or ketone derivatives of a polyhydroxyalcohol. 

Epimers of D glucose

C2 - mannose

C3 - allose

C4 - galactose

axial groups and equatorial groups

haworth projections 

Model to show 3D structure of sugars in 2D form

chair configuration

Another model to show 3D structure of sugars in 2D form - note that it is more difficult to see which bonds are up and which are down facing

Alpha and beta sugars

Carbon numbering on haworth models

Carbon numbering on chair models