Download BIO 330 Cell Biology Lecture Outline Spring 2011 Chapter 9

BIO 330 Cell Biology
Lecture Outline
Spring 2011
Chapter 9: Glycolysis and Fermentation
I. Metabolism
A. Anabolic pathways
Endergonic
B. Catabolic pathways
Exergonic
Create metabolites
II. ATP
A. Phosphoanhydride bonds
Hydrolysis splits 2nd bond
Exergonic: G = -7.3 kcal/mol
B. ATP/ADP
Energy release / storage
III. Chemotrophic Energy Metabolism
A. Biological oxidation
Removal of electrons (and protons, i.e., H atoms)
Dehydrogenation / dehydrogenases
B. Reduction
Addition of electrons (and protons…)
Hydrogenation / hydrogenases
C. Redox reactions
Oxidation and reduction happen simultaneously
D. Electron acceptors
Coenzymes
NAD+  NADH
E. Glucose oxidation
Stepwise release of free energy
G = -686 kcal/mol
IV. Glycolysis and Fermentation
A. Glycolytic pathway
10 reactions converting 1 glucose to two pyruvate molecules
3 phases
Preparation and cleavage
Add 2 phosphates to glucose via 2 ATP
Hexokinase – 1st step; rate-limiting enzyme
Phosphofructokinase-1 (PFK-1) (site of regulation)
Aldolase – splits 1 6-C molecules into 2 3-C molecules
Oxidation and ATP generation
BIO 330 Cell Biology
Lecture Outline
Spring 2011
Substrate-level phosphorylation
Phosphoglycerate kinase creates ATP
NADH is produced
Pyruvate formation and ATP generation
Phosphoenolpyruvate hydrolysis by pyruvate kinase
B. Pyruvate oxidation to Acetyl CoA
In presence of oxygen
Preparation for entry to Krebs cycle (citric acid cycle; tricarboxylic acid cycle)
C. Fermentation
In absence of oxygen
Pyruvate is reduced by NADH to regenerate NAD+
Lactate fermentation
Lactate dehydrogenase works in either direction depending on
prevailing conditions in the cell
Lactic acid produced in muscle is carried to liver and reincorporated into
glucose via gluconeogenesis
Lactic acid in bacteria can be used commercially for dairy products
Alcoholic fermentation
Pyruvate loses CO2 to become ethanol
Pyruvate decarboxylase
Alcohol dehydrogenase
Alcoholic fermentation by yeast is used in baking and alcohol production
No net oxidation occurs
2 ATP produced per glucose molecule
V. Alternative Glycolysis Substrates
A. Alternative substrates are converted to metabolic intermediates
Proteins and lipids are converted to intermediates of the TCA cycle
Carbohydrate substrates are converted to intermediates of glycolysis
B. Other sugars and glycerol
Fructose, galactose, mannose are common alternatives
Polysaccharides and disaccharides are converted to monosaccharides
Monosaccharides are converted to intermediates
Pentoses must be converted to hexoses
Phosphogluconate pathway (pentose phosphate pathway)
Glycerol is converted to dihydroxyacetone phosphate
C. Polysaccharides
Phosphorolytic cleavage
Similar to hydrolysis, using phosphate instead of water
VI. Gluconeogenesis
BIO 330 Cell Biology
Lecture Outline
Spring 2011
Synthesis of glucose from 3-C or 4-C precursors
Similar to “reverse glycolysis”
3 very endergonic steps require different enzymes
Bypass reactions
G6Pase (glucose-6-phosphatase)
FBPase (fructose-1,6-bisphosphatase)
PEPCK (phosphoenolpyruvate)
PC (pyruvate carboxylase)
VII. Regulation of Glycolysis and Gluconeogenesis
A. Spatial separation
Glycolysis and gluconeogenesis occur in different cells / tissues
B. Regulation
Allosteric regulation of enzyme activity
Glycolysis
Hexokinase
PFK-1
Pyruvat e kinase
Gluconeogenesis
FBPase
Pyruvate carboxylase
AMP and Acetyl CoA regulate both pathways
C. Fructose-2,6-bisphosphate regulation of glycolysis and gluconeogenesis
Phosphofructokinase (PFK) 2 is a bifunctional enzyme
cAMP inhibits PFK 2 indirectly with regards to its kinase activity
cAMP upregulates PKF 2 indirectly with regards to its phosphatase activity