Term
| What tissues are involved in gluconeogenesis? |
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Definition
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Term
| In what subcellular compartments does gluconeogenesis occur? |
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Definition
| Cytosol, mitochondria, and endoplasmic reticulum |
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Term
| What are the three irreversible enzymes of glycolysis that have to be circumvented in Gluconeogenesis? |
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Definition
| Pyruvate Kinase, Phosphofructokinase 1, and Hexokinase (Glucokinase) |
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Term
| How is the irreversible pyruvate kinase step of glycolysis circumvented in gluconeogenesis? |
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Definition
2 enzymes: pyruvate carboxylase and phosphoenolpyruvate carboxykinase
pyruvate -> oxaloacetate (intermediate)
via pyruvate carboxylase
oxoacetate -> phosphoenolpyruvate
via phosphophenolpyruvate carboxykinase |
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Term
| How is the irreversible phosphofructokinase-1 step of glycolysis circumvented in gluconeogenesis? |
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Definition
by the enzyme Fructose 1,6 biphosphatase
Fructose 1,6 Biphosphate-> Fructose 6-phosphate
via Fructose 1,6 biphosphatase |
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Term
| How is the irreversible hexokinase (specifically glucokinase [liver]) step circumvented in gluconeogenesis? |
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Definition
enzyme Glucose 6-phosphatase
glucose 6-phosphate -> Glucose |
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Term
| What cofacter do all carboxylases need? |
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Definition
| What is the final step of glycogenolysis in the muscles?Biotin, one of the B-complexes |
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Term
| What is the biggest cause of Biotin deficiency? |
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Definition
| Binding of avidin (protein) to biotin. Abnormally high levels of avidin present in the system of patients who consume many raw egg whites |
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Term
| How does biotin deficiency present? |
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Definition
| Allopecia, scaly dermititis, and waxy pallor |
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Term
| what is the last enzyme in hepatic glycogenolysis? |
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Definition
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Term
| What enzyme of gluconeogenesis is found in the endoplasmic reticulum? |
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Definition
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Term
| What enzymes of gluconeogenesis that circumvent the irreversible steps of glycolysis are found in the cytosol? |
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Definition
| phosphoenolpyruvate carboxykinase and Fructose 1,6 biphosphatase |
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Term
| What enzyme of gluconeogenesis is found in the mitochondria? |
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Definition
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Term
| What enzyme of gluconeogenesis that circumvents an irreversible step of glycolysis consumes GTP? |
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Definition
| Phosphoenolpyruvate carboxykinase |
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Term
| What enzyme of gluconeogenesis that circumvents an irreversible step of glycolysis consumes ATP? |
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Definition
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Term
| What is the net consumption if gluconeogenesis? What process provides this energy? |
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Definition
4 ATP, 2 GTP, 2 NADH
Process is beta oxidation |
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Term
| What is the presentation of a patient that has an gluconeogenic enzyme deficiency? |
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Definition
| Fasting hypoglycemia with lactic acidosis, hyperuricemia, hyperlipidemia, and ketosis |
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Term
| Why does lactic acidosis occur in patients with a gluconeogenic enzyme deficiency? |
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Definition
| The breakdown in gluconeogenesis will eventually force substrate back into pyruvate which can reversible retrovert back to lactate and alanine |
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Term
| Why do patients with gluconeogenic enzyme deficiency present with hyperuricemia? |
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Definition
| The hyperuricemia is secondary to the lactic acidosis. Elevated lactate levels supress the ability of the kidney to excrete uric acid |
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Term
| Why do patients with a gluconeogenic enzyme deficiency present with hyperlipidemia and ketosis? |
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Definition
| The presenting hypoglycemia will cause a drop in insulin levels. This lower insulin will upregulate (via glucagon) the release and metabolism of triglycerides (via beta oxidation and ketogenesis) which will result in the hyperlipidemia and ketosis |
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Term
| What is the clinical test for gluconeogenic enzyme deficieny? |
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Definition
| Infusion with alanine and subsequent monitoring of blood glucose. If the blood glucose level rises then the patient is normal, if the level remains the same then the patient could have a enzyme disorder of gluconeogenesis |
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Term
| What is a good way to narrow down the culpable enzyme in a patient with gluconeogenic enzyme deficiency? |
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Definition
| Infusion of glycerol and subsequent monitoring of blood glucose. If the glucose rises then the enzyme culpable is earlier in the chain: either a problem with Pyruvate Carboxylase or a problem with Phosphoenolpyruvate Carboxykinase. If the blood sugar does not rise then the problem is with either: Glucose 6-phosphatase or Fructuse 1-6 biphosphatase |
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