Glycolysis: Allowed abbreviations

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Glycolysis: Allowed abbreviations. Glucose Glucose 6-phosphate Fructose 6-phosphate Fructose 1,6-bisphosphate Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate 1,3-Bisphosphoglycerate 3-phosphoglycerate 2-phosphoglycerate Phosphoenolpyruvate Pyruvate. N/A G-6P F-6P F-1,6BP - PowerPoint PPT Presentation

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Glycolysis: Allowed abbreviationsGlucoseGlucose 6-phosphateFructose 6-phosphateFructose 1,6-bisphosphate Dihydroxyacetone phosphateGlyceraldehyde 3-phosphate1,3-Bisphosphoglycerate3-phosphoglycerate2-phosphoglyceratePhosphoenolpyruvatePyruvate

N/AG-6PF-6PF-1,6BPDHAPG-3P1,3-BPG3-PG2-PGPEPN/AFates of Other Sugars

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GLUCONEOGENESIS5

Gluconeogenesis Synthesis of "new glucose" from common metabolites Humans consume 160 g of glucose per day 75% of that is in the brain Body fluids contain only 20 g of glucose Glycogen stores yield 180-200 g of glucose So the body must be able to make its own glucose 73

8Substrates for Gluconeogenesis Pyruvate, lactate, glycerol, amino acids and all TCA intermediates can be utilized Fatty acids cannot!Why?Most fatty acids yield only acetyl-CoA Acetyl-CoA (through TCA cycle) cannot provide for net synthesis of sugars 94Gluconeogenesis Occurs mainly in liver and kidneys Not the mere reversal of glycolysis for 2 reasons:

Energetics must change to make gluconeogenesis favorable (delta G of glycolysis = -74 kJ/mol

Reciprocal regulation must turn one on and the other off - this requires something new!105Gluconeogenesis Something Borrowed, Something New Seven steps of glycolysis are retained:

Steps 2 and 4-9 Three steps are replaced or bypassed:

Steps 1, 3, and 10 (the regulated steps!)The new reactions provide for a spontaneous pathway (G negative in the direction of sugar synthesis), and they provide new mechanisms of regulation Make sure you know the THREE BYPASS STEPS of Gluconeogenesis116

1st bypass reaction:Pyruvate PEPPyruvate is converted back to PEP in two steps.Not shown here is the transport process: since oxaloacetate is usually found in the mitochondrial matrix, it must be transported out into the cytosol. However, there is no transporter for oxaloacetate.1st bypass reaction:Pyruvate PEPTherefore, oxaloacetate is reduced to malate first using malate dehydrogenase.Malate is transported out into the cytosol and then reoxidized back to oxaloacetate

2nd bypass reaction:Fructose 1,6-Bisphosphate Fructose 6-phosphateTechnically the reverse of the glycolytic reaction, but it is mediated by a different enzyme.

Mediated by a different enzyme.2nd bypass reaction:Glucose 6-Phosphate GlucoseCori cycle

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18Pentose Phosphate Pathway19