GluconeogenesisGlucose Synthesis is Required for Survival •Brain is dependent on glucose 120g/day...
Transcript of GluconeogenesisGlucose Synthesis is Required for Survival •Brain is dependent on glucose 120g/day...
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Gluconeogenesis
• Suggested Reading:
• Lippincot’s Ilustrated reviews: Biochemistry
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Glucose Synthesis is Required for Survival
• Brain is dependent on glucose 120g/day
• Body glucose reserve is limited≈ 20 g (extra cellular fluid)
≈ 75 g ( liver glycogen); enough for 16 hours
≈ 400 g (muscle glycogen); for muscle use only
Main source of energy for resting muscle in postabsobtivestate is fatty acids. 80% of glucose is used by brain & rbc
• 70 Kg man has ≈ 15 Kg fat – Fatty acids can not be converted to glucose
– Utilization of FA is increased 4-5 X in prolonged fasting
– In prolonged fasting; FA ➔ ketone bodies at high rate
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Gluconeogenesis occurs mainly in the liver
Tissues that do not oxidize glc. completelye.g RBCExcercising muscle
Muscle A.Acids
Adipose tissue
Lactate
alanine
glycerol
Glucose
Peripheral tissues
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Lactate Pyruvate Amino acids
Amino acids oxaloacetate propionate
Glycerol Triosephosphates Fructose
Galactose Glucose
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Glucose
Glucose 6-phosphate
Fructose 1,6- bisphosphate
2 Phosphoenolpyruvate
Oxaloacetate
2 Pyruvate
Fructose 6-phosphate
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Carboxylation of Pyruvate Produces Oxaloacetate
ADPATP >CO2
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Formation and Hydrolysis of Glucose 6-phosphate
Glc. + Pi Glc. 6-phosphate + H2O ΔG = +veATP + H2O ADP + Pi ΔG = -ve
Glc. + ATP Glc. 6-phosphate + ADP ΔG = -ve
Glc. 6-phosphate + H2O Glc. + Pi ΔG = -ve
HK
Phosphatase
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Glucose
Glucose 6-phosphate
Fructose 1,6- bisphosphate
2 Phosphoenolpyruvate
Oxaloacetate
2 Pyruvate
Fructose 6-phosphate
ATP
GTP
ATP X 2
X 2
X 2
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T
2 ADP2 ATP
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The Cori Cycle
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PFK
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Pyruvate kinase
Pyruvate carboxylase
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Next topic: Glycogen Metabolism
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