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-Metabolism and Sugars

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									Metabolism and Sugars
        4/2/03
 Carbohydrate and sugar structure
Carbohydrates or saccharides are essential
components of living organisms.
(C•H2O)n Where n=3 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
Monosaccharides (D-aldoses)
    The Fischer convention, the basis for the D-
    configuration in sugars comes from D-glyceraldhyde’s
    configuration around its asymmetric carbon.
                  1 CHO                 1 CHO

              H
                   2      OH        H
                                         2       OH

                   3                    3
            HO            H        HO            H

                   4                    4
              H           OH        H            OH

                   5                     5
              H           OH       HO            H

                  6 CH 2OH              6
                                            CH 2OH


                  D-glucose             L-glucose

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 2 n-2
stereoisomers
 Carbohydrates are classified as to the nature of the
 carbonyl group : ketone = ketose aldehyde = aldose
                                   Triose
2(n-3)
stereoisomers
of ketoses
                                   Tetrose


                                   Pentose




                                   Hexose
Monosaccharides can form ring structures




             O              O




            Furan       Pyran
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
Sugar Polymers The Polysacchrides

• Energy Storage
  – Starch a-amylose and amypectin
• Structural
  – Cellulose and Chitin
• Glycosaminoglycans
• Proteoglycans
a-amylose
Cellulose (polyglucose)
Glycosaminoglycans & Proteoglycans
Bacteria Cell Walls
Peptidoglycan
                 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?
Phototrophs- acquire free energy from sunlight


Chemotrophs - oxidize organic compounds to
make


                   ATP
     ATP is the energy carrier for most
            biological reactions
A road map of
  metabolic
  pathways.
              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.
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
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.
    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
                  A              rates.
1                              2
                                The need to control the
           Y          X         amounts of either 1 or 2
                                independent of each other.

								
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