CARBOHYDRATES
Carbohydrate Classifications:
Monosaccharides - sweeteners; building blocks of larger carbohydrates.
Simple carbohydrates - cannot be hydrolyzed.
dihydroxyacetone; D-glyceride; D-glucose; D-galactose; D-fructose
Individual saccharides can be joined by glycosidic linkages. Prefix indicates how many
saccharides are linked together — di-, tri-, tetra-, penta-, hexa-, heptasaccharide...
Complex carbohydrates - can be hydrolyzed into smaller carbohydrates.
maltose; cellobiose; lactose; sucrose
Polysaccharides - more than 10 saccharides.
starch (amylose, amylopectin, glycogen); cellulose
Saccharide - polyhydroxyaldehyde or polyhydroxyketone with the formula (CH2O)n
where n = 3, 4, 5, ...
-ose: suffix used in most monosaccharide names (i.e. glucose) and designations (see below).
Aldose or Ketose: indicates that the saccharide is an aldehyde or a ketone, respectively.
Tri-, tetr-, pent-, hex-, or heptose: indicates the number of carbons in a saccharide.
These designations can be combined with aldo or keto listed first. Examples: aldotriose;
ketoheptose.
D or L configuration of a saccharide is determined by the position of the oxygen on the last
chiral center. Left is L; Right is D. For cyclic saccharides look for the CH2OH: Up is D;
Down is L. (See examples on Glucose page.)
Cyclic Saccharides - formed when a hydroxyl group reacts at the carbonyl carbon
pyranose: cyclic monosaccharide having a six atom ring
furanose: cyclic monosaccharide having a five atom ring
anomeric carbon: the carbon bonded to two oxygens in the structures below.
α or β configuration of cyclic saccharides is determined by the position of the oxygen on the
anomeric carbon: Up is β; Down is α. (See examples on Glucose page.)
Hemiacetal: can be recognized by the presence of an OH on the anomeric carbon. Ring readily
reopens.
Acetal: can be recognized by the absence of an OH on the anomeric carbon. Ring “locked”
closed.
hemiacetal
acetal
CH 2OH
O OH
HO
anomeric carbon
OH
OH
R stands for a carbon
CH 2OH
or a carbon chain
O OR
HO
anomeric carbon
OH
OH
Reducing Sugar - a saccharide that will reduce Benedict's solution (oxidizing the saccharide). This
includes cyclic hemiacetals of saccharides as well as the open chain forms of saccharides on
the following pages. Acetals do not with Benedict’s solution.