BCH210H1 Lecture Notes - Lecture 24: Anomer, Glycosidic Bond, Lone Pair
25 May 2018
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Lecture 24: Carbohydrates and complex sugars
• Monosaccharide – 1 sugar
• Disaccharide – 2 sugars
• Oligosaccharide – 3 to 20 sugars
• Polysaccharides 1000s of sugars
Disaccharide Formation
• Anomeric carbon considered hemiacetal
• Intermolecular reaction – two sugars coming together
• Lone pair from one of the hydroxyl will attach anomeric carbon → full acetal
• New functional group – glycosidic bond → lose a water molecule
Condensation Reaction
• H2O released (hydroxyl on C4 or C1 lost to form H2O)
• Glycosidic linkage = no longer use the formula
• Left sugar no longer a reducing sugar – anomeric carbon IN glycosidic bond
where we no longer can break into linear form
• Right sugar is still a reducing sugar – can still break and open up linearly
Variation on the O-glycosidic Bond
• Could also have something that is NOT sugar
- Methanol with hydroxyl will attack anomeric C
- Still lose H2O molecule
N-Glycosidic Bond
• Sugars can be bound to amino acids (ser,thr)
- Both have hydroxyl groups on them
• Lone pair on nitrogen will attack sugar to form a
new glycosidic linkage → attach sugars like
asparagine
Review – Glycosidic Bonds
• Monosaccharides are joined by o-glycosidic
linkages to form disaccharides/sugar polymers
• Intermolecular o-glycosidic bonds are formed
between a hydroxyl group and an anomeric carbon
• Condensation reaction where water is lost
• Di = 2, oligo = 3-20, poly = 1000s
• Glycoproteins may be o-linked (ser/thr) or N-
linked (asn)
- Added in the ER and modified in the Golgi
find more resources at oneclass.com
find more resources at oneclass.com
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BCH210H1 Full Course Notes
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Document Summary
Lecture 24: carbohydrates and complex sugars: monosaccharide 1 sugar, disaccharide 2 sugars, oligosaccharide 3 to 20 sugars, polysaccharides 1000s of sugars. Disaccharide formation: anomeric carbon considered hemiacetal, new functional group glycosidic bond lose a water molecule. Lone pair from one of the hydroxyl will attach anomeric carbon full acetal. Condensation reaction: h2o released (hydroxyl on c4 or c1 lost to form h2o, glycosidic linkage = no longer use the formula. Left sugar no longer a reducing sugar anomeric carbon in glycosidic bond where we no longer can break into linear form: right sugar is still a reducing sugar can still break and open up linearly. Variation on the o-glycosidic bond: could also have something that is not sugar. Methanol with hydroxyl will attack anomeric c. N-glycosidic bond: sugars can be bound to amino acids (ser,thr) Both have hydroxyl groups on them: lone pair on nitrogen will attack sugar to form a new glycosidic linkage attach sugars like asparagine.
