Term
| Identify two pathways which form "free" glucose and predict the physiological consequences of an enzyme deficiency that inhibits one or both of the pathways |
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Definition
1) Gluconeogenesis
2) Glycogen degradation
-A deficiency in the enzymes of these pathways would cause hypoglycemia, especially between meals |
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Term
| Identify the tissues which supply each of the major gluconeogenic precursors and physiological conditions that favor production of glucose from each precursor. |
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Definition
Lactate: general metabolism, RBC metabolism, muscle metabolism
Glucogenic amino acids: overnight degradation of muscle amino acids
Glycerol: Degradation of triacylglycerol (adiopse tissue) |
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Term
| Explain why fatty acids with an even number of carbons DO NOT increase the net synthesis of glucose |
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Definition
| Do not give anything new that can be used to make glucose (like TCA cycle); TCA cycle does not add anything new. |
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Term
| Predict the consequences of glycolysis and gluconeogenesis occurring simultaneously in the same cell |
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Definition
| - inefficient: breaking down glucose just to use the energy from it just to build it back up. |
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Term
| Predict the tissues that will utilize much of the glucose formed by gluconeogenesis during a prolonged fast or as a result of active exercise |
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Definition
Active exercise: skeletal muscle
Prolonged fast: Brain |
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Term
| Identify the substrate whose oxidation provides much of the ATP needed for gluconeogenesis |
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Definition
| lactate->pyruvate->oxaloacetate |
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Term
| Describe the relationship of gluconeogenesis from from amino acids to ureagenesis |
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Definition
| The formation of pyruvate involves transamination and removal of NH2, which must be taken up in the urea cycle |
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Term
| Identify the four enzymes that catalyze the three irreversible steps of gluconeogenesis |
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Definition
1)Pyruvate caboxylase
Pyruvate->Oxaloacetate
2) Phophoenolpyruvate carboxykinase
Oxaloacetate->Phosphoenolpyruvate
3) Fructose-1,6-bisphosphate
Frc-1,6-bisphosphate-> Frc-6-phosphate
4) Glucose-6-phosphatase
Glc-6-phosphate->Glucose |
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Term
| Compare the allosteric regulation of glycolysis and gluconeogenesis |
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Definition
There is less of it in gluconeogensis, but essentially, things that activate the enzymes of glycolysis will inhibit their glucneogenic counter parts:
EG: Frc-2,6-bisphosphate activates PFK1, but inhibits fructose-1,6-bisphosphatase. |
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Term
| Predict the effects of insulin and glucagon on the regulation of key glycolytic and gluconeogenic enzymes and on the synthesis of these enzymes |
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Definition
| glucagon inhibits expression of glycolytic enzymes in the liver and upregulates gluconeogenic enzymes. |
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Term
| Identify the specific response element that likely mediates the effects of glucagon on gene transcription |
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Definition
| cAMP response element (CRE) is the gene, probably upregulated by phosphorylation of CREB (cAMP response element binding protein) |
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Term
| Explain how ethanol metabolism reduces the concentration of two intermediates in gluconeogenesis |
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Definition
Ethanol gets converted to acetaldehyde, generating NADH. This changes the NADH/NAD+ ratio in the cell:
Result: both reactions get shifted right, taking away glucneogenesis intermediates)
Pyruvate + NADH -> Lactate + NAD+
Oxaloacetate + NADH -> Malate + NAD+ |
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