Metabolism and Sugars
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)
The Fischer convention, the basis for the D-
configuration in sugars comes from D-glyceraldhyde’s configuration around its asymmetric carbon.
CHO
D-glucose L-glucose 1
Epimers differ in configuration around one carbon atom i.e. D-glucose and D-mannose but D-glactose and D-D-glucose are not
epimers because they very around two carbon atoms. There are 2n-2
Carbohydrates are classified as to the nature of the carbonyl group : ketone = ketose aldehyde = aldose
Triose
Tetrose
Pentose
Hexose
2(n-3)
Monosaccharides can form ring structures
O O
Glycosidic binds are between two sugars
They can either be in the or configuration and
Sugar Polymers The Polysacchrides
• Energy Storage
– Starch -amylose and amypectin
• Structural
– Cellulose and Chitin
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
Phototrophs- acquire free energy from sunlight
Chemotrophs - oxidize organic compounds to
make
ATP
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.
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
Certain pathways are involved in both
breakdown and buildup of molecules these
pathways are called
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
X
Y
Independent routes means independent control of
rates.
