Chemistry 501 Handout 14 Glycolysis, Gluconeogenesis, and

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Chemistry 501 Handout 14 Glycolysis,
Gluconeogenesis, and the Pentose Phosphate
PathwayChapter 14
Lehninger. Principles of Biochemistry. by Nelson
and Cox, 5th Edition W.H. Freeman and Company
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Major pathways of glucose utilization
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The first phase of glycolysis (the preparatory
phase)
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The second phase of glycolysis (the payoff phase)
O
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The two phases of glycolysis
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Three possible catabolic fates of the pyruvate
formed in glycolysis
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1. Phosphorylation of glucose
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2. Conversion of glucose 6-phosphate to fructose
6-phosphate
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The phosphohexose isomerase reaction
anomeric carbon
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3. Phosphorylation of fructose 6-phosphate to
fructose 1,6-bisphosphate
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4. Cleavage of fructose 1,6-bisphosphate
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The class I aldolase reaction
imine
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5. Interconversion of the triose phosphates
Fate of the glucose carbons in the formation of
glyceraldehyde 3-phosphate
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6. Oxidation of glyceraldehyde 3-phosphate to
1,3-bisphosphoglycerate
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The glyceraldehyde 3-phosphate dehydrogenase
reaction
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7. Phosphoryl transfer from 1,3-bisphosphoglycera
te to ADP
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8. Conversion of 3-phosphoglycerate to
2-phosphoglycerate
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The phosphoglycerate mutase reaction
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9. Dehydration of 2-phosphoglycerate to
phosphoenolpyruvate
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10. Transfer of the phosphoryl group from
phosphoenolpyruvate to ADP
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Entry of glycogen, starch, disaccharides, and
hexoses into the preparatory stage of glycolysis
Feeder pathways for glycolysis
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Feeder pathways for glycolysis
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Dietary polysaccharides and disaccharides undergo
hydrolysis to monosaccharides
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Glycogen breakdown by glycogen phosphorylase
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Other monosaccharides enter the glycolytic
pathway at several points
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Conversion of galactose to glucose 1-phosphate
Defects in any of the three enzymes in this
phatway Cause galactosemia in humans
Galactose methabolite involved in
galactokinase-deficiency galactosemia
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Fates of pyruvate under anaerobic conditions
Fermentation
Pyruvate is the terminal electron acceptor in
lactic acid fermentation
no net change in NAD or NADH
acidification in muscle and blood limits
the period of vigorous activity
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Ethanol is the reduced product in ethanol
fermentation
tightly bound coenzyme, thiamine pyrophosphate
Industrial-scale fermentations yield a variety of
common foods and industrial chemicals
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The alcohol dehydrogenase reaction
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Thiamine pyrophosphate (TPP) and its role in
pyruvate decarboxylation
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Thiamine pyrophosphate
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Gluconeogenesis
Carbohydrate synthesis from simple precursors
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Opposing pathways of glycolysis and
gluconeogenesis in rat liver
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Synthesis of phosphoenolpyruvate from pyruvate
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Role of biotin in the pyruvate carboxylase
reaction
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Alternative paths from pyruvate to
phosphoenolpyruvate
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Citric acid intermediates and many amino acids
are glucogenic
Citrate Isocitrate a-ketoglutarate Succinyl-CoA Su
ccinate Fumarate Malate
Pyruvate
oxaloacetate
C.A.C.
Amino acid catabolism
C.A.C. Intermediates
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Feeder pathways for glycolysis (preparatory phase)
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General scheme of the pentose phosphate pathway
of glucose oxidation
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Oxidative reactions of the pentose phosphate
pathway
NADP
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Nonoxidative reactions of the pentose phosphate
pathway
The nonoxidative phase recycles pentose
phosphates to glucose 6-phosphate
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The first reaction catalyzed by transketolase
thiamine pyrophosphate
General reaction Transfer of a two-carbon group
from a ketose donor to an aldose acceptor
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The reaction catalyzed by transaldolase
The second reaction catalyzed by transketolase
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Role of NADPH in regulating the partitioning of
glucose 6-phosphate between glycolysis and the
pentose phosphate pathway
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Role of NADPH and glutathione (GSH) in protecting
cells against highly reactive oxygen derivatives