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21 Cards in this Set
- Front
- Back
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What are the primary precursors of gluconeogenesis?
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Alanine
Lactate Glycerol pyruvate oxaloacetate |
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Where does gluconeogenesis occur in a cell?
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cytosol
mitochondria lumen of ER |
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What is the main purpose of gluconeogenesis?
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synthesize glucose from non-carbohydrate precursors. This is important when metabolic needs for glucose are not met with the body's storage of carbohydrates alone
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What is the daily requirement for glucose for the body? for the brain? How much glucose is available in glycogen?
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for the body: 160g
for the brain: 120g available in glycogen: 190g |
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What organ is the major site of gluconeogenesis?
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Liver
also can occur in kidney cortex |
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What enzyme of gluconeogenesis is from the mitochondria while all others are from the cytosol?
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pyruvate carboxylase
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How does glycerol enter the gluconeogenesis pathway?
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Triacylglyercols are broken down into fatty acids and glycerol. FAs undergo beta oxidation to acetyl CoA while glycerol undergoes the following reactions:
Glycerol----->(glycerol kinase) glycerol phosphate----->(glycerol phosphate dehydrogenase) dihydroxyacetone phosphate |
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How does oxaloacetate enter the gluconeogenesis pathway?
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malate--->(malate dehydrogenase) oxaloacetate
or ASN--->ASP--->(transaminase) oxaloacetate |
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How does lactate enter the gluconeogenesis pathway?
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lactate---> (lactate dehydrogenase) pyruvate
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How does alanine enter the gluconeogenesis pathway?
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alanine--->(alanine aminotransferase) pyruvate
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How does alcoholism inhibit gluconeogenesis?
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You need NAD+ to have glycerol enter the gluconeogenesis pathway but all the ethanol uses the NAD+ --->acetaldehyde--->acetate--->acetyl CoA
The NADH released from the rxn ethanol--->acetaldehyde drives pyruvated to make lactate (enzyme lactate dehydrogenase) |
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What enzymes are involved in the irreversible steps of glycolysis? When enzymes serves as the reverse role of these enzymes in gluconeogenesis?
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hexokinase: glucose 6- phosphatase
phosphofructokinase: fructose 1,6 phosphatase pyruvate kinase: pyruvate--->(pyruvate carboxylase) oxaloacetate--->(phosphoenolpyruvate carboxykinase) phosphoenolpyruvate |
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What is the structure of pyruvate carboxylase?
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It has a biotin carrier domain that moves from the ATP grasp domain where biotin is carboxylated to the carboxylase transferase domain where biotin transfers carboylate to pyruvate to make oxaloacetate.
allosteric domain where acetyl CoA binds which is required for carboxylation |
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Where does the reaction of pyruvate--->oxaloactetate occur?
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mitochondria matrix
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Why is oxaloactetate first converted into malate and back to oxaloacetate before being converted to phosphoenolpyruvate?
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The rxn pyruvate--->oxaloacetate occurs in the matrix of the mitochondria. There aren't transporters for oxaloacetate but there are for malate so it is briefly converted just to transport out of the mitochondria
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What is the net reaction of pyruvate to PEP?
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pyruvate +CO2 + ATP +H20---->oxaloacetate + ADP +Pi + 2H+
oxaloacetate + GTP ---> PEP + GDP + CO2 Pyruvate + ATP + GTP + H20 --->PEP + ADP + GDP + 2Pi + 2H+ |
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What hormone induces phosphoenolpyruvate carboxykinase?
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glucagon
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Where does the rxn fructose 1,6 bisphosphate ----> fructose 6-phosphate (enzyme fructose 6-phosphatase) occur?
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lumen of the ER
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How many ATP? GTP? NADH? and water does it take for gluconeogenesis?
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4 ATP
2 GTP 2 NADH 6 H20 |
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Where does gluconeogenesis get all of this energy to supply the rxns?
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Fatty acids that are converted to Acetyl CoA via B oxidation.
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What is the cori cycle?
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Liver synthesizes glucose via gluconeogenesis while muscles use the glucose made by LV and release lactate (exercising muscle). That lactate is taken up by LV to make glucose
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