BCH 3120 Lecture Notes - Lecture 2: Anomer, Pyranose, Triose
28 Apr 2018
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January 11, 2017
Carbohydrates and Glycolysis
Carbohydrates
Have molecular formula CxH2xOx
-Polyols: have lots of alcohols
-1 degree of unsaturation
Aldose: carbohydrates with an aldehyde
Ketose: carbohydrates with a ketone
Monomeric and polymeric:
-Monosaccharides: formed of a single unit (ex. glucose)
-Disaccharides: formed of 2 units (ex. Sucrose = glucose + fructose)
-Oligosaccharides: short chains (from 3 to several units)
•Structure is non-repetitive and complex
•Often linked to non-carbohydrate molecules (ex. Glycoproteins and glycolipids)
-Polysaccharides: long chain
•Structure is repetitive and simple, linear
Most form cyclic structures: 6-member ring pyranoses, 5-member ring furanoses
-Ex. Glucose forms a pyranose
•
-Anomeric carbon is used to determine stereochemistry
•D: highest priority is on right
•L: highest priority is on left
•α: OH is axial
•β: OH is equatorial
Carbohydrate Classification by Number of Carbons
n = 3: triose
CHO
HOH
C
CH2OH
HO H
HOH
HOH
O
C
CH2OH
OH
OH
OH
OH
anomeric carbon:
reactive centre
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January 11, 2017
n = 4: tetrose
N = 5: pentose
n = 6: hexose
-Ex. Aldohexose, ketohexose
N = 7: heptose
n = 8: octose
Key Monosaccharides
Numbered from top to bottom (1 at top)
Manose: C2 epimer of glucose
Galactose: C4 epimer of glucose
Disaccharides
2 sugars linked by glycosidic bond at anomeric carbon
-Anomeric carbon is linked to an O
OO
OH
HO
OH
OH
HO
OH
OH
OH
O
OH OH
OH
OH
HO
HO
HO
Glucose Mannose Galactose
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January 11, 2017
Polysaccharides
Can have branching
Can have more complex sugars
Cellulose: Beta(1—>4) sugar
-Linkage through carbon 1 and 4 of Beta conformation of glucose
Roles of Carbohydrates
Structural role: carbohydrate fibres or gels support and protect biological structures
-Cellulose: plant cell walls
-Glycosaminoglycans: tendons and cartilage
Energetic role: main fuel
-Also other metabolites
Functional role: carbohydrates on the cell surface are the main mediators of cell-cell interactions
-Glycobiology: studies how carbohydrates mediate biological functions
Carbohydrate Metabolism: Glycolysis
Glucose + 2 ADP + 2 Pi + 2 NAD+ —> 2 pyruvate + 2 ATP + 2 NADH + 2 H2O + H+
10 enzymes
Starts with glucose and produces pyruvate
Net production of 2 pyruvate molecules, 2 NADH, and 2 ATP
-Production of ATP is substrate level phosphorylation: formation by direct addition of phosphoryl groups
Broken up into 2 parts: phase I and phase II
Phase I: energy investment phase
-Uses 1 glucose, produces 2 units of GAP, uses 2 units of ATP
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Document Summary
Monosaccharides: formed of a single unit (ex. glucose) Oligosaccharides: short chains (from 3 to several units: structure is non-repetitive and complex, often linked to non-carbohydrate molecules (ex. Polysaccharides: long chain: structure is repetitive and simple, linear. Most form cyclic structures: 6-member ring pyranoses, 5-member ring furanoses. Anomeric carbon is used to determine stereochemistry: d: highest priority is on right, l: highest priority is on left, : oh is axial, : oh is equatorial. Carbohydrate classification by number of carbons n = 3: triose. N = 5: pentose n = 6: hexose. N = 7: heptose n = 8: octose. Numbered from top to bottom (1 at top) 2 sugars linked by glycosidic bond at anomeric carbon. Anomeric carbon is linked to an o. Linkage through carbon 1 and 4 of beta conformation of glucose. Structural role: carbohydrate bres or gels support and protect biological structures. Functional role: carbohydrates on the cell surface are the main mediators of cell-cell interactions.
