Three Fates of Pyruvate

1. Three Fates of Pyruvate • Pyruvate  acetyl-CoA • Occurs in mitochondria • Produce CO2 and NADH + H+ • Pyruvate Dehydrogenase • Aerobic • **Acetyl-CoA used in the TCA cycle

2. Three Fates of Pyruvate • Pyruvate  Lactate • Produce CO2 and NAD+ • Homolactic fermentation • Anaerobic • Pyruvate  Ethanol • Produce CO2 and NAD+ • Alcoholic fermentation • Anaerobic

3. Citric Acid Cycle • 8 reactions • Oxidize acetyl groups • Acetyl groups come from many sources (not just carbohydrates) • “Hub” of cellular metabolism • Intermediates are precursors for the biosynthesis of other compounds • 3 NAD++FAD+GDP+Pi+acetyl-CoA 3 NADH+FADH2+GTP+CoA+2 CO2

4. Citric Acid Cycle • Reaction 1 • Oxaloacetate (OAA) + acetyl-CoA + H2O Citrate + CoASH • Citrate synthase • Condensation • Reaction 2 • Citrate  Isocitrate • Aconitase • Isomerization

5. Citric Acid Cycle • Reaction 3 • Isocitrate + NAD+ Ketoglutarate (KG) + NADH + H+ + CO2 • Isocitrate dehydrogenase • Dehydrogenation and oxidative decarboxylation • Reaction 4 • Ketoglutarate + CoASH + NAD+ Succinyl-CoA + NADH + H+ + CO2 • Ketoglutarate dehydrogenase • Dehydrogenation and oxidative decarboxylation

6. Citric Acid Cycle • Reaction 5 • Succinyl-CoA + GDP + Pi Succinate +GTP + CoASH • Succinyl-CoA synthetase • Substrate level phosphorylation via coupling reactions • Reaction 6 • Succinate + FAD  Fumarate + FADH2 • succinate dehydrogenase • Dehydrogenation

7. Citric Acid Cycle • Reaction 7 • Fumarate + H2O  Malate • Fumarase • Hydration • Reaction 8 • Malate  Oxaloacetate • Malate dehydrogenase • Dehydrogenation

8. ATP Production • NADH : ATP  1 : 3 • FADH2 : ATP  1 : 2 • GTP : ATP  1 : 1

9. Summary of ATP Produced