Ch 4 Carb Structure And Function Flashcards
Monosaccharides
Most basic structural unit of carbs
Formula is Cn(H2O)n
Trioses
Tetroses
Pentoses
Hexoses
Simplest monosaccharides containing three Cs
Tetroses contain 4 Cs
Pentoses contain 5
Hexoses contain 6
Aldoses
Carbs that contain aldehydes as their most oxidized functional group
Ketoses
Carbs that contain alcohols with ketones as their most oxidized functional group
Glyceraldehyde
Simplest Aldose - an aldotriose
A polyhydroxylated aldehyde
Dihydroxyacetone
Simplest ketose also participates in glycosidic bonds
Commonly tested carbs
D-Fructose
D-glucose
D-galactose
D-mannose
Optical isomers
Also called stereoisomers
All share chemical formula
Enantiomers
Share chemical formula and are nonsuperimposable, nonidentical, mirror images of each other
Same sugar in different optical families
D and L naming convention
D-+ has a positive rotation
L-+ has negative
All D sugars in Fischer projection have hydroxide of their highest numbered chiral center on right and L sugars have that hydroxide on the left
Diastereomers
Two sugars that are in the same family (both ketoses or both aldoses with same number of carbons) that are not identical and are not mirror images
Epimers
A special subtype of diastereomers that differ in configuration at exactly one chiral center
Equation for number of stereoisomers with a common backbone for a given molecule
2 to the power n
Where n = number of chiral carbons.
Hemiacetals
And hemiketals
Monosaccharides have an Oh group (nucleophile) and a CO group (electrophile)
And can therefore undergo intramolecular reactions to form cyclic hemiacetals (from aldoses) and hemiketals (from ketoses)
Pyranose
And furanose
Six-membered and 5-membered rings respectively - only cyclic molecules that are stable in solution due to ring strain
Anomeric carbon
Carbonyl carbon that becomes chiral in the process of formation of either a hemiacetal or hemiketal
Anomers
Two molecules that differ at the anomeric carbon
Alpha anomer
In glucose, has the oh group is C-1 trans to the -CH2OH substituent (axial and down)
Left
Beta anomer
Has -OH group of C-1 cis to the -CH2OH substituent (equatorial and up)
Right