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6 Cards in this Set
- Front
- Back
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What are the metabolic purposes of glycolysis? |
1) extract energy quantally from glucose via small transformations 2) produce derivatives useful for other small molecule synthesis |
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Explain how the well-fed state (reflected as sufficient blood glucose) promotes glycolysis. |
Glucose enters the muscle cells from the blood by release of insulin. Insulin also activates hexokinase to turn glucose into glc-6-phosphate and thus promotes glycolysis. |
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Explain how the fasting state inhibits glycolysis. |
Low blood glucose=low levels of insulin, so insulin will not activate hexokinase. PFK-1 will not be activated because of allosteric regulation. |
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Compare the mechanisms that up-regulate glycolysis over different time-scales. |
Insulin upregulates glycolysis by activating hexokinase when blood glucose is high. PFK-1 upregulates glycolysis when it is activated: when ATP is low or AMP or ADP is high (during fed state). glyceraldehyde 3-phosphate + inorganic phosphate --> 1,3-bisphosphoglycerate + ADP --> 3-phosphoglycerate + ATP :is favorable because the net delta G is negative. This is substrate phosphorylation bc ATP is directly generated! Pyruvate kinase generates ATP through substrate level phosphorylation also, delta G is neg. |
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Explain how the glycolytic pathway accommodates hypoxia. |
Hypoxia (lack of oxygen) up regulates glycolysis.
During hypoxic or anaerobic conditions, pyruvate is converted into lactate through fermentation (in vigorously contracting muscle, and other cells). When lactate dehydrogenate converts pyruvate to lactate, NAD+ is produced and can be used in glycolysis to produce 1,3-bisphosphoglycerate. |
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Explain the multiple roles of phosphorylation for glycolytic intermediates, and for regulation of glycolysis. |
A phosphorylation event (to glucose 6-phosphate by hexokinase) traps glucose inside the cell so it can be used for glycolysis. PFK-1 phosphorylates fructose 6-phosphate to fructose 1,6-bisphosphate and this represents the commitment step in glycolysis. PFK-1 is regulated by phosphorylation/ dephosphorylation. ATP is generated by substrate level phosphorylation by phosphoglycerate kinase and pyruvate kinase. |
