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12 Cards in this Set

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