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Fate of Pyruvate & Citric Acid Cycle

Fate of Pyruvate & Citric Acid Cycle. Introduction of Glucose Metabolism Lecture-3. Fate of pyruvate. 1- Lactate (in cytosol ) Enzyme: lactate dehyrogenase (LDH) in anaerobic glycolysis 2- Acetyl CoA in mitochondria Enzyme: pyruvate dehydrogenase

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Fate of Pyruvate & Citric Acid Cycle

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  1. Fate of Pyruvate& Citric Acid Cycle Introduction of Glucose Metabolism Lecture-3

  2. Fate of pyruvate 1- Lactate(in cytosol) Enzyme: lactate dehyrogenase (LDH) in anaerobic glycolysis 2- Acetyl CoA in mitochondria Enzyme: pyruvatedehydrogenase occurs in aerobic glycolysis Acetyl CoA is required for citric acid cycle (CAC) 3- Oxalacetate in mitochondria Enzyme: pyruvatecarboxylase Oxalacetate is required for: 1- Citric acid cycle (condenses with acetyl CoA): to yield energy ATP OR2-Gluconeogenesis (to synthesize glucose)

  3. Fate of Pyruvate Glucose glycolysis Gluconeogenesis No Oxygen No Mitochondria OR BOTH PYRUVATE mitochondria LACTATE OXALACETATE Oxygen & Mitochondria ACETYL CoA CITRIC ACID CYCLE

  4. Formation of acetyl CoA from pyruvate • Pyruvate (end product of aerobic glycolysis) is transported into the mitochondria. • In the mitochondrial matrix, pyruvate is converted to acetyl CoAby pyruvatedehydrogenase complex (multienzyme complex) This reaction is irreversible • Pyruvatedehydrogenase complex is composed of three enzymes & five coenzymes • Coenzymes of the complex are derived from water soluble vitamins: 1- Thiamine pyruphosphate, TPP (derived from thiamine, vitamin B1) 2- NAD+ (derived from niacin) 3- FAD (derived from riboflavin) 4- Lipoic acid 5- Coenzyme A (derived from pantothenic acid)

  5. Pyruvatedehydrogenase complex PYRUVATE ACETYL CoA

  6. Citric acid cycle or,(Krebs cycle)

  7. Citric Acid Cycle Citric acid cycle is the final pathway where the oxidative metabolism of Carbohydrates (as glucose), proteins (amino acids) & lipids (fatty acids) to yield energy (ATP) Acetyl CoAis the end product for oxidation of carbohydrates, lipids & proteins Acetyl CoAcondenses with oxalacetateto form citrate (first reaction of the cycle) 3 NADH are produced = 3 X 3 = 9 ATP (by oxidative phosphorylation) One FADH2 is produced = 1 X 2 = 2 ATP (by oxidative phosphorylation) One ATP is produced (by substrate level phosphorylation) Net = 12 ATP / one acetyl CoA

  8. Citric Acid Cycle CYCLE - SUMMARY Acetyl CoA 3 NAD 3 NADH + H 2 CO2 1 FAD 1 FADH2 1 ADP 1 ATP

  9. Citric acid cycle or,(Krebs cycle)

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