Carbohydrates
Structure and Function
• How do we define a carbohydrate?
• aldehydes or ketones with multiple hydroxyl groups
• “hydrate” of carbon – C-H2O
• What are some of the functions of carbohydrates?
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fuel for cells
storage of energy
cell structure
metabolic intermediates
cell-cell recognition
Monosaccharides
• How is an aldose different from a ketose?
• H-C=O versus C=O
• How do we classify monosaccharides?
• number of carbon atoms (3-9)
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trioses
tetroses
pentoses
hexoses
Monosaccharides
• What are enantiomers?
• D and L forms – D and L designate configuration of
asymmetric carbon farthest from aldehyde or ketone
group
Aldoses
Ketoses
Cyclization of Monosaccharides
• Aldehydes react with alcohols to form hemiacetals
Cyclization of Monosaccharides
• Aldohexoses such as glucose can form
intramolecular hemiacetals.
Cyclization of Monosaccharides
• Ketones react with alcohols to form hemiketals.
Cyclization of Monosaccharides
• Ketohexoses such as fructose can form
intramolecular hemiketals.
Cyclization of Monosaccharides
• Cyclization creates a second asymmetric
carbon atom
• -D-glucopyranose and -D-glucopyranose
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depends upon position of group at carbon 1
C – 1 is anomeric carbon
 means hydroxyl group is below plane of ring
 means hydroxyl group is above plane of ring
• -D-fructofuranose and -D-fructofuranose
• C – 2 is anomeric carbon
Cyclization of Monosaccharides
• Fructose can form both 5-membered furanose and
6-membered pyranose rings
Monosaccharides
• To what do the terms chair ,boat , and
envelope refer?
Monosaccharides
• What are glycosidic bonds?
• formed from reaction of monosaccharide with alcohol
or with amine
Monosaccharides
• What are reducing sugars?
• sugars that have free aldehyde group that are easily
oxidized by oxidizing agents such as Cu+2
Disaccharides
• How are disaccharides formed?
Disaccharides
• What are the most common disaccharides?
• sucrose
• maltose
• lactose
Disaccharides
Disaccharides
Disaccharides
Polysaccharides
• What do glycogen and starch have in
common?
• polymers of glucose
• homopolymers
• How are glycogen and starch different?
• glycogen - major storage form in animals
• starch – major storage form in plants
Polysaccharides
Polysaccharides
• What is the difference between amylose and
amylopectin?
• amylose is unbranched and amylopectin has branches
Polysaccharides
• How is cellulose similar to and different
from starch?
• both found in plants
• both made of glucose units
• cellulose is structural, starch is nutritional
• starch contains  linkages and cellulose 
linkages
Polysaccharides
Polysaccharides
• What are glycosaminoglycans?
• polysaccharides made of repeating units of
disaccharides containing a derivative of an
amino sugar
• one of the sugars in unit has negatively charged
carboxylate or sulfate group
• usually attached to proteins
• proteoglycans
Glycosaminoglycans
Oligosaccharide Formation
• What are
glycosyltransferases?
• enzymes that catalyze
formation of glycosidic
bonds
Glycosyltransferases
• What is the connection between these
enzymes and the human blood groups?
• A, B, and O blood groups have different
oligosaccharides attached to glycoproteins and
glycolipids on surface
• A and B have one extra monosaccharide unit
added by glycosyltransferase
Glycosyltransferases