1. Metabolism and Sugars
4/2/03

2. 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

3. Monosaccharides (D-aldoses)

4. The Fischer convention, the basis for the D-
configuration in sugars comes from D-glyceraldhyde’s
configuration around its asymmetric carbon.
CHO
OHH
HHO
OHH
OHH
CH2OH
CHO
OHH
HHO
OHH
HHO
CH2OH
D-glucose L-glucose
1
2
3
4
5
6
1
2
3
4
5
6
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

5. 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

6. Monosaccharides can form ring structures
O O
PyranFuran

10. Glycosidic binds are between two sugars
They can either be in the α or β configuration and
can be linked through the 1-2, 1-4 or 1-6 linkage

11. Sugar Polymers The Polysacchrides
• Energy Storage
– Starch α-amylose and amypectin
• Structural
– Cellulose and Chitin
• Glycosaminoglycans
• Proteoglycans

12. α-amylose

13. Cellulose (polyglucose)

14. Glycosaminoglycans & Proteoglycans

15. Bacteria Cell Walls

16. Peptidoglycan

17. 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?

18. Phototrophs- acquire free energy from sunlight
Chemotrophs - oxidize organic compounds to
make
ATP
ATP is the energy carrier for most
biological reactions

19. A road map of
metabolic
pathways.

21. 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.

22. 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

23. 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.

24. 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!
1
A
2
XY
Independent routes means
independent control of
rates.
The need to control the
amounts of either 1 or 2
independent of each other.