Central Metabolic Pathways

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Central Metabolic Pathways

• Review

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Glycolysis and TCA Cycle
glucose (C6)
Glycolysis
2 ATP
2 ADP P
TCA Cycle
2 C3
2 NAD
Formation of Acetyl CoA
2 ADP P
2 NADH
2 ATP
2 C2 (acetyl CoA)
2 ADP P
2 C6
2 CO2
2 NADH
2 ATP
2 acetyl groups (C2)
2 pyruvate (C3)
2 CO2
2 C5
2 C4
2 NAD
2 NADH
2 NADH
2 CO2
2 ATP
2 NADH
2 FADH2
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Glycolysis
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Stage I of Glycolysis
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Metabolism of Glucose-6-P
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Summary of Stage I
Glucose 2 ATP gt 2 GA3P 2 ADP
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Stage II of Glycolysis
Substrate Level Phosphorylation
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Stage II of Glycolysis
3PGA gt Serine, Cysteine and Glycine PEP gt
Aromatic Amino Acids
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Stage II of Glycolysis
Substrate Level Phosphorylation Pyruvate gt
Alanine
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Summary of Stage II
2 GA3P 2 NAD 4 ADP 2 Pi
2 Pyruvate 2 NADH 2 H 4 ATP
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Summary of Glycolysis
Glucose 2 NAD 2 ADP 2 Pi
2 Pyruvate 2 NADH 2 H 2 ATP
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Recycling of NADH

• Anaerobic Fate of Pyruvate

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Homolactate Fermentation
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Alcoholic Fermentation
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Energetics of Fermentation
Glucose gt 2 Lactate Glucose 6 O2 gt 6 CO2
6 H2O
?Go -200 kJ/mol ?Go -2866 kJ/mol
Most of the energy of glucose is still available
following glycolysis!
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Glycolysis and TCA Cycle
glucose (C6)
Glycolysis
2 ATP
2 ADP P
TCA Cycle
2 C3
2 NAD
Formation of Acetyl CoA
2 ADP P
2 NADH
2 ATP
2 C2 (acetyl CoA)
2 ADP P
2 C6
2 CO2
2 NADH
2 ATP
2 acetyl groups (C2)
2 pyruvate (C3)
2 CO2
2 C5
2 C4
2 NAD
2 NADH
2 NADH
2 CO2
2 ATP
2 NADH
2 FADH2
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Citric Acid Cycle(TCA Cycle)(Krebs Cycle)
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Amphibolic Nature of TCA Cycle
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Summary of TCA Cycle
Acetyl-CoA 3 NAD FAD GDP Pi
2 CO2 3 NADH 3H FADH2 GTP CoA-SH
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Generation of TCA Cycle Intermediates
Animals and Some Bacteria
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Generation of TCA Cycle Intermediates(Glyoxylate
Cycle)
Plants and Some Microorganisms
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Net Reaction of Glyoxylate Cycle
Net increase of one 4-carbon unit!
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Electron TransportOxidative Phosphorylation
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Sequence of Electron Transport

• Complex I NADH-CoQ Reductase
• Complex II Succinate-CoQ Reductase(Succinate
  Dehydrogenase)
• Complex III CoQ-Cytochrome c Reductase
• Complex IV Cytochrome Oxidase

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Location of Electron Transport

• Bacterial Plasma Membrane
• Mitochondrial Inner Membrane

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Oxidative Phosphorylation
Proton Pumping
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Chemiosmotic Hypothesis

• Proton Pumping
• Electrochemical Gradient
• FoF1-ATPase (conformational coupling)
• ATP-ADP Translocase

Coupling of Electron Transport and Oxidative
Phosphorylation
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Regulation of Central Metabolic Pathways