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12 Cards in this Set
- Front
- Back
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what are the advantages of having glycogen as a glucose source
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readily accessible, broken down quickly to maintain blood glucose levels, readily mobilized and plentiful source, provides energy in anaerobic conditions because glucose can be used in the absence of oxygen
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what are the three steps to glycogen degredation
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1. the release of glucose 1 phosphate
2. remodeling of the glycogen substrate 3. formation of glucose 6 phosphate from glucose 1 phosphate |
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what are the fates of glucose 1 phosphate derived from glycogen
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glycolysis
PPP hydrolyzed to glucose to be released into blood |
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draw a structure showing the most common linkage between glucose units found in glycogen
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at least to glucose molecules with alpha 14 linkages (down) between them
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why is the formation of glucose 1 phosphate energetically favorable even though the delta G is very small
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it is favored because the ration of phosphate to glucose 1 phosphate is greater than 100 to 1
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why can't the glucose 1 phosphate diffuse out of the cell
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the negative charge keeps it trapped and there are no membrane transporters
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why does the liver possess specific enzymes that can cleave glucose 6 phosphate to form glucose and phosphate
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the phosphate must be removed so glucose can leave the cell because the liver controls blood glucose levels
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why must glycogen control be manifested differently in muscle and liver
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muscle maintains glucose for itself, liver maintains glucose for the entire organism
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by what mechanism is phosphorylase kinase activated by Ca2+ levels
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when the delta subunit binds to calcium ions and the beta subunit is phosphorylated the kinase molecule obtains maximum activity
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give the reaction catalyzed by UDP glucose pyrophosphorylase
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glucose 1 phosphate + UTP --> UDP glucose + PPi (pyrophosphate)
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how does insulin stimulate glycogen synthesis
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insulin triggers a pathway that activates kinases, which phosphorylate and inactivate glycogen synthase kinase, which can no longer deactivate glycogen synthase so the enzyme is activate and able to synthesize glycogen
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why creation of UDP glucose is irreversible
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because pyrophosphate (PPi) will hydrolyze into two phosphate molecules
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