Metabolism and Sugars 4/2/03

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Metabolism and Sugars4/2/03
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Carbohydrate and sugar structure
Carbohydrates or saccharides are essential
components of living organisms. (CH2O)n Where
n3 or greater. A single saccharide is called a
monosaccharide. Oligosaccharide is a few linked
monosaccharides and are at time associated with
proteins (glycoproteins) or lipids
(glycolipids) Polysaccharides consist of many
monosaccharides i.e. cellulose or glycogen
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Monosaccharides (D-aldoses)
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The Fischer convention, the basis for the D-
configuration in sugars comes from
D-glyceraldhydes configuration around its
asymmetric carbon.
Epimers differ in configuration around one
carbon atom i.e. D-glucose and D-mannose but
D-glactose and D-glucose are not epimers because
they very around two carbon atoms. There are 2n-2
stereoisomers
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Carbohydrates are classified as to the nature of
the carbonyl group ketone ketose aldehyde
aldose
Triose Tetrose Pentose Hexose
2(n-3) stereoisomers of ketoses
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Monosaccharides can form ring structures
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Glycosidic binds are between two sugars
They can either be in the a or b configuration
and can be linked through the 1-2, 1-4 or 1-6
linkage
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Sugar Polymers The Polysacchrides

• Energy Storage
• Starch a-amylose and amypectin
• Structural
• Cellulose and Chitin
• Glycosaminoglycans
• Proteoglycans

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a-amylose
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Cellulose (polyglucose)
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Glycosaminoglycans Proteoglycans
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Bacteria Cell Walls
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Peptidoglycan
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Metabolism
Metabolism is the overall process through which
living systems acquire and utilize free energy to
carry out their functions
The coupling of exergonic reactions of nutrient
breakdown to the endergonic processes is required
to maintain the living state
How do living things acquire the energy needed
for these functions?
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Phototrophs- acquire free energy from
sunlight Chemotrophs - oxidize organic compounds
to make ATP ATP is the energy carrier for most
biological reactions
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A road map of metabolic pathways.
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Metabolic pathways
A series of consecutive biochemical reactions
catalyzed by enzymes that produce a specific end
product. Catabolism- the breakdown of food stuffs
to simple organic chemicals. Anabolism- the
synthesis of biomolecules from simple organic
chemicals. The breakdown of foods converge to a
few simple compounds.
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• Very Few metabolites are used to synthesize a
  large variety of biomolecules
• Acetyl-Coenzyme A (acetyl-CoA)
• Pyruvate
• Citrate acid cycle intermediates
• Three main pathways for energy production
• Glycolysis
• Citric acid cycle
• Oxidative-Phosphorylation

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Certain pathways are involved in both breakdown
and buildup of molecules these pathways are
called amphibolic. The citric acid cycle is an
example of this.
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Metabolic pathways are irreversible
They have large negative free energy changes to
prevent them running at equilibrium. If two
pathways are interconvertible (from 1 to 2 or 2
to 1), the two pathways must be different!
Independent routes means independent control of
rates.
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2
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The need to control the amounts of either 1 or 2
independent of each other.
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Y