Term
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Definition
- the human body stores about 1-2% glycogen
- prolonged fasting or vigorous exercise will quickly deplete reserves of glycogen from the liver and muscles
- human body must invariable synthesize additional glucose from other raw materials
- muscles have 2-3% glycogen; liver stores 8-10% glycogen |
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Term
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Definition
- the production of new glucose from non-carbohydrate derived products of catabolism
- catabolic products include proteins, glycerolipids, and anaerobic respiration products like pyruvic acid/lactic acid
- gluconeogenesis occurs primarily in the liver in animals and germinating oilseeds in plants |
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Term
| gluconeogenesis as a reversal of glycolysis |
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Definition
- glucneogenesis is energetically expensive, but physiologically necessary
- occurs when blood sugar is low
- glycolysis and gluconeo.. occur in separate areas |
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Term
| Gluconeogenesis from lactic acid |
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Definition
- the cori cycle
- main function is to convert lactic acid from strenuous exercise/low oxygen back into glucose
- normally thermodynamically preferred to go to lactate but a high NAD(+) ratio to NADH makes it thermodynamically favorable to go to pyruvate and NADH |
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Term
| Gluconeogenesis from Alanine |
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Definition
- the glucose-alanine cycle
- alanine serves as a carrier of pyruvate carbon and toxic NH_3 from the muscles to the liver where pyruvate enters gluconeogenesis and NH3 is discarded as urea |
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Term
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Definition
| - moves the NH3 to convert L-Alanine to pyruvate or the reverse |
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Term
| Gluconeogenesis from glycerol |
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Definition
- glycerol comes from triglycerides
- two steps to return to gluconeogenesis
1. glycerol kinase
2. glycerol phosphate dehydrogenase |
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Term
| Glycolysis vs. gluconeogenesis |
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Definition
| - glycolysis is in the cytosol while gluconeogenesis is compartmentalized in the cytosol, mitochondria and ER (glyoxysomes in plants) |
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Term
| regulatory rxns in glycolysis |
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Definition
| irreversible, its why gluconeogenesis is necessary |
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Term
| allosteric enzymes/regulation of gluconeogenesis |
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Definition
| pyruvate carboxylase, fructose - bis phosphate phosphatase |
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Term
| Regulatory reactions of gluconeogenesis |
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Definition
- synthesis of PEP regulated by the processes involved in the creation of oxaloacetate (pyruvate carboxylase and PEP carboxykinase)
- other by-pass reactions |
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Term
| Role of mitochondrion in gluconeogenesis |
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Definition
1. pyruvate processing
- conversion to PEP
- conversion to malate
2. physiological strategy
- insure adequate supply of NADH for gluconeogenesis becasue gald-3P requires lots of NADH
- one starts with NAD and the other with NADH so that no matter what the levels in the body it can occur |
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Term
| The role of the endoplasmic reticulum in gluconeogenesis |
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Definition
- hydrolysis of glucose-6P by Glucose-6P phosphatase
- the glucose is released into the blood stream after it is hydrolyzed in the ER |
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Term
| Regulation of Gluconeogenesis |
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Definition
2 modes:
1. Allosteric Control
2. Hormonal Control |
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Term
| Regulation of PFK1 vs. Fructose-BP-Phosphatase |
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Definition
1. gluconeogenesis side
- F-2, 6-P2 inhibits
- citrate stimulates
- AMP inhibits
2. Glycolysis side
- F-2, 6-P2 stimulates
- Citrate inhibits
- AMP stimulates |
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Term
| Hormonal control of glucose metabolism |
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Definition
- high glucagon inhibits glycolysis and stimulates gluconeogenesis
- high insulin stimulates glycolysis and glucose uptake |
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Term
| Hormones involved in glucose metabolism |
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Definition
- insulin
- glucagon
- adrenalin (stimulates massive release of glucose) |
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Term
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Definition
| ensure optimum blood glucose levels |
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Term
| Gluconeogenesis in plants |
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Definition
- occurs in chloroplasts during photosynthesis
- associated with germinating oilseeds
- sucrose is the final product instead of glucose
- requires interactions between lipid bodies, glyoxysomes, mitochondria and cytosol |
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Term
| main steps of plant gluconeogenesis |
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Definition
triglycerides to
fatty acids to
acetyl-CoA (two) to
succinate to
malate to
PEP to
gluconeogenesis to
sucrose |
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Term
| The pentose-phosphate pathway |
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Definition
an alternate pathway for oxidation (catabolism) of glucose except that
- does not produce ATP
- produces NADPH
- produces pentose sugars
- produces intermediates that can feed into glycolysis |
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Term
| oxidative phase of pentose phosphate pathway |
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Definition
- cytosolic NADPH for biosynth of fatty acids, anti-oxidant activity
- produces pentose sugars for nucleic acid biosynthesis and cell wall components |
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Term
| glycogen and starch synthesis |
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Definition
**phosphoglucomutase converts glucose-6P to glucose-1P
- that is activated to UDP-glucose (makes glycogen) and ADP-glucose (makes starch) |
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