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46 Cards in this Set
- Front
- Back
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What is the structure of glycogen?
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α 1,4 linkages between a number of glucoses with branching; α 1-6 branch points occur every 8 to 12 residues
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What I the requirement for hydrolization of glucoses off glycogen?
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non-reducing ends
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What's the primary difference between the starches (amlose and amylopectin) and glycogen?
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starches have much less branching
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How and where is glycogen stored?
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liver, muscle, and some kidne in cytosolic storage granules
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What different role does glycogen serve in muscle and liver?
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glycogen in muscle is for use in muscle (it has no glucose-6-phosphatase), glycogen in liver is for mobilization of glucose systemically
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How much glycogen is stored in the liver (activity wise)?
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About 12 hours or so
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How much glycogen is stored in the liver (activity wise)?
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About 1 hour
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What enzyme is primarily responsible for glycogen degradation?
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glycogen phosphorylase (highly regulated)
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What enzyme is required for degradation of glycogen 4 glucose units away from a branch point?
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debranching enzyme, transfers about 4 units to a longer unbranched end (leaving the glucose with the α 1,6 bond)
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Which enzyme trims the glucose at a 1->6 branchpoint?
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α-1,6 glucosidase
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What's the product of glycogen phosphorylase?
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glucose-1-P
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What enzyme catalyzes the glucose-1-P to glucose-6-P reaction (or vice-versa in synthesis)?
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phosphoglucomutase (reversible)
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Which enzyme can remove a phosphate from glucose-6-P for mobilization?
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glucose-6-phosphatase (primarily in the liver, in kidney for kidney only)
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Enzyme that attaches UDP to glucose-1-P and provides the energy for the addition of glucose-1-P to non-reducing end of the glycogen chain.
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glucose 1-phosphate uridyltransferase
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enzyme that adds a glucose off a high energy nucleotide sugar to the non-reducing end of glycogen (irreversible)
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glycogen synthase
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a protein at the reducing end of glycogen that provides scaffolding and works as an enzyme primer to allow for glycogen synthase to add additional glucoses
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glycogenin
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enzyme that takes 6-mer glucoses and greater from the nonreducing end and transfers them to the nearest C-6
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branching enzyme
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a glycogen storage disease associated with glucose-6-phosphatase that leads to severe fastig hypoglycemia and an enlarged liver
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von Gierke disease (Type I)
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a glycogen storage disease that leads to an accumulation of glycogen due to a lack of lysosomal α-1,4-glucosidase and ultimately results in death from massive cardiomegaly at an early age
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Pompe disease (Type II)
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a glycogen storage disease caused by deficiencies in glycogen debranching enzyme; simalr to von Gierke's, but milder hypglycemia
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Cori disease (Type III)
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a glycogen storage disease cause by deficiencies of glycogen branching enzyme; leads to hepatosplenomegaly and is usually fatal
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Andersen disease (Type IV)
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a glycogen storage disease that manifests as exercise induced muscle pain and cramps due to deficincies in muscle glycogen phosphorylase
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McArdle disease (Type V)
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a glycogen storage disease associated with deficits in liver glycogen phosphorylase; leads to hepatomegaly, mild hypoglycemia (generally has a good prognosis)
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Hers disease (Type VI)
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hormone responsible for signalling the formation of glycogen in the liver and muscle in the fed state
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insulin
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hormone responsible for the breakdown of glycogen in the liver in the fasted state
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glucagon
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signal responsible for the breakdown of glycogen in muscle and liver in times of stress, fear, and injury
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epinephrine
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signal responsible for the breakdown of glycogen in muscle and liver during stress and exercise
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Ca2+
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state in which key enzymes are phosphorylated
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Fasted state (by glucagon)
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state in which key enzymes are dephosphorylated
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Fed state (by insulin)
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key glycogen enzyme(s) that are turned on in the fasted state
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glycogen phosphorylase and phosphorylase kinase
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key glycogen enzyme(s) that are turned off in the fasted state
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glycogen synthase
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key glycogen enzyme(s) that are turned on in the fed state
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glycogen synthase
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key glycogen enzyme(s) that are turned off in the fed state
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glycogen phosphorylase & phosporylase kinase
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receptor for glucagon
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7-TM protein (G-protein) that stimulates the synthesis of cAMP via adenylate cyclase
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critical protein that is activated by a downstream signal of glucagon via cAMP
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protein kinase A
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breaksdown cAMP
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phosphodiesterase
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inhibits phosphodiesterase
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cAMP
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enzyme that is stimulated by insulin
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protein phosphatase 1
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protein that dephosphorylates glycogen synthase
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protein phosphatase 1
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mechanism by which glycogn metabolism enzymes are primarily regulated in the muscle
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calcium (calmodulin) release stimulated by exercise induces protein kinases to phosphorylate phosphorylate kinase, glycogen phosphorylase, and glycogen synthase
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allosteric activator of glycogen phosphorylase in the muscle
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AMP
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a signalling protein that decreases cAMP levels
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insulin
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in what tissue is glucose intake upregulated by insulin and by what mechanism
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GLUT4 is upregulated in muscle tissue allowing for greater glucose uptake
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allosterically activates phosphorylase kinase
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Ca2+
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what extracellular messenenger is responsible for initiating the cAMP dependent glycogenolytic cascade in muscle?
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epinephrine (via β receptors)
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what can be a result of maternal malnutrition (relative to glycogen synthesis)
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neonatal hypoglycemia
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