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Gluconeogenesis

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Gluconeogenesis

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Gluconeogenesis

  1. 1. For more Visit us: www.dentaltutor.in For more Visit us: www.dentaltutor.in
  2. 2.  Gluconeogenesis makes glucose from non-carbohydrate starting materials ◦ Lactate ◦ Glycerol ◦ Most amino acids (not leucine, lysine) ◦ Glycerol and amino acids are used only in starvation conditions  Process occurs primarily in the liver For more Visit us: www.dentaltutor.in
  3. 3. The gluconeogenic pathway converts pyruvate into glucose. pyruvate glucose→→ → → → gluconeogenesis glycolysis Gluconeogenesis is not a reversal of glycolysisFor more Visit us: www.dentaltutor.in
  4. 4.  While basically opposite processes glycolysis and gluconeogenesis are not a simple reversal of each other  The three nonreversible steps of glycolysis must be bypassed with new routes ◦ Pyruvate  Phosphoenolpyruvate ◦ Fructose-1,6-bisphosphate  Fructose-6- phosphate ◦ Glucose-6-phosphate  Glucose For more Visit us: www.dentaltutor.in
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  6. 6. •The two enzymes that catalyze the reactions for bypass of the Pyruvate Kinase reaction are the following: •Pyruvate Carboxylase (Gluconeogenesis) catalyzes: pyruvate + HCO3 - + ATP  oxaloacetate + ADP + Pi •PEP Carboxykinase (Gluconeogenesis) catalyzes: oxaloacetate + GTP  PEP + GDP + CO2 C C CH2 O O- OPO3 2- C C CH3 O O- O ATP ADP + Pi C CH2 C C O O O- O- O HCO3 - GTP GDP CO2 pyruvate oxaloacetate PEP Pyruvate Carboxylase PEP Carboxykinase For more Visit us: www.dentaltutor.in
  7. 7.  Fructose 6-phosphate is formed from 1,6-bisphosphate by hydrolysis of the phosphate ester at carbon1.  Fructose 1,6-bisphosphatase catalyzes this exergonic hydrolysis Fructose 1,6-bisphosphate + H2O  fructose 6-phosphate + Pi For more Visit us: www.dentaltutor.in
  8. 8.  Glucose is formed by the hydrolysis of gulcose 6-phosphate in a reaction catalyzed by gulcose 6-phosphatase Gulose 6-phosphate + H2O  gulcose + Pi For more Visit us: www.dentaltutor.in
  9. 9. Glyceraldehyde-3-phosphate Dehydrogenase Phosphoglycerate Kinase Enolase PEP Carboxykinase glyceraldehyde-3-phosphate NAD+ + Pi NADH + H+ 1,3-bisphosphoglycerate ADP ATP 3-phosphoglycerate Phosphoglycerate Mutase 2-phosphoglycerate H2O phosphoenolpyruvate CO2 + GDP GTP oxaloacetate Pi + ADP HCO3 - + ATP pyruvate Pyruvate Carboxylase Gluconeogenesis Summary of Gluconeogenesis Pathway: Gluconeogenesis enzyme names in red. Glycolysis enzyme names in blue. For more Visit us: www.dentaltutor.in
  10. 10. Glucose-6-phosphatase Fructose-1,6-bisphosphatase glucose Gluconeogenesis Pi H2O glucose-6-phosphate Phosphoglucose Isomerase fructose-6-phosphate Pi H2O fructose-1,6-bisphosphate Aldolase glyceraldehyde-3-phosphate + dihydroxyacetone-phosphate Triosephosphate Isomerase (continued) For more Visit us: www.dentaltutor.in
  11. 11.  Step 3 of glycolysis: ◦ Catalyzed by phosphofructokinase ◦ Stimulated by: high AMP, ADP, Pi ◦ Inhibited by: high ATP  Reverse occurs in gluconeogenesis: ◦ Fructose-1,6-bisphosphatase stimulated by high ATP ◦ At times of excess energy (high ATP) gluconeogenesis is favored For more Visit us: www.dentaltutor.in
  12. 12. Reciprocal regulation of gluconeogenesis and glycolysis in the liver. The interconversion of fructose 6-phosphate and fructose 1,6- bisphosphate is stringently controlled The interconversion of phosphoenolpyruvate and pyruvate also is precisely regulated. For more Visit us: www.dentaltutor.in
  13. 13.  In the Cori cycle, ◦ Lactate from skeletal muscle is transferred to the liver ◦ Converted to pyruvate then glucose ◦ This glucose can be returned to the muscle
  14. 14. THANKS  For more Visit us: www.dentaltutor.in

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