Term
| 3 steps in the initial breakdown of glycogen to glucose |
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Definition
| glycogen --> glucose-1-phosphate --> glucose 6-phosphate |
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Term
| 2 enzymes coordinately regulated for the regulation of glycogen metabolism |
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Definition
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Term
| what enzyme controls phosphorylation hormonal control for glycogen metabolism |
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Definition
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Term
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Definition
| controls phosphorylation/dephosphorylation events |
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Term
| contrast the effect of phosphorylation on glycogen phosphorylase vs glycogen synthase activity |
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Definition
| increases glycogen phosphorylase activity, decreases glycogen synthase activity |
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Term
| towards what process does phosphorylation flux glycogen activity |
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Definition
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Term
| what does liver tissue respond to? |
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Definition
| only [glucose] (NOT own energy state, not ATP & AMP levels) |
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Term
| Why does liver tissue not respond to energy charge? |
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Definition
| it doesn't vary metabolically |
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Term
| Does AAMP activate liver phosphorylase? |
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Definition
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Term
| How does glucose binding affect liver phosphorylase? |
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Definition
| glucose binding inactivates phosphorylase by shifting the equilibrium from R to T |
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Term
| What is the main structure of glycogen synthase? |
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Definition
| a tetramer of identical subunits |
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Term
| two conformations of glycogen synthase |
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Definition
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Term
| What is an activating allosteric modulator of glycogen synthase? |
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Definition
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Term
| 3 allosteric inhibitors of glycogen synthase |
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Definition
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Term
| How does dephosphorylation affect glycogen synthase? |
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Definition
| phosphorylation turns OFF synthase |
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Term
| How does phosphorylation affect phosphorylase? |
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Definition
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Term
| type O glycogen storage disease (identified 1964) |
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Definition
| characterized by morning drowsiness, fatigue, convulsions due to hypoglycemia (low blood sugar), high levels of blood glucose & lactase after meals |
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|
Term
| causes of type O glycogen storage disease |
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Definition
| liver deficient in glycogen & a lack of glycogen synthase |
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Term
| Are synthesis (anabolic) & degradative (catabolic) pathways dependent or independent? |
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Definition
| independent, but somehow they must communicate |
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Term
| Are glycogen granules highly or lowly hydrated (surrounded by water)? |
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Definition
| highly hydrated; OH groups cause H bonding |
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Term
| Why is the T conformation of glycogen phosphorylase less active? |
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Definition
| it has a buried active site & low substrate affinity |
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Term
| Why is the R conformation of glycogen phosphorylase more active? |
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Definition
| it has an accessible active site & high substrate affinity |
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Term
| allosteric activators of glycogen phosphorylase |
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Definition
| AMP (indicates low energy) which promotes move to more active |
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Term
| 3 allosteric inhibitors of glycogen phosphorylase |
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Definition
| ATP, glucose 6-P, & glucose prevents the move to more active |
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Term
| Where does AMP bind for glycogen phosphorylase & what does it do? |
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Definition
| the allosteric site in the T state to promote the T to R conformational change |
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Term
| Where do inhibitors bind for glycogen phosphorylase & what do they do? |
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Definition
| the allosteric site in T state to prevent T to R conformational change |
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Term
| What is released by pancreas in response to low blood sugar? |
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Definition
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Term
| What is released by adrenal cortex in response to stress? |
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Definition
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Term
| 2 epinephrine receptors on liver cells |
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Definition
1. activates cAMP --> second messenger that activates enzyme needed for phosphorylation
2. triggers Ca2+ release --> partially activates protein kinase a |
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Term
| How does epinephrine act on muscle receptors? |
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Definition
| activates beta-adrenergic receptor, causing release of camp |
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Term
| When is insulin released? |
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Definition
| in response to high blood glucose |
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Term
| How does insulin binding affect muscle? |
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Definition
| it binds the insulin receptor, activates kinases that inactivate glycogen synthase kinase, drives pathway towards glycogenesis |
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Term
| 2 activities controlled by glycogen debranching enzyme |
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Definition
1. alpha (1-4) transglycolase (transfer of alpha (1-4) trisaccharide to non-reducing end of glycogen)
2. alpha (1-6) glycosidase (removes alpha (1-6) bound glucose at branching point in a hydrolysis reaction) |
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Term
|
Definition
| an isomerase that catalyzes reversible conversion of glucose-1-P to glucose-6-P |
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|
Term
| Where is glucose-6-phosphatase primarily found? |
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Definition
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Term
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Definition
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Term
| 3 enzymes involved in glycogenolysis |
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Definition
1. glycogen phosphorylase
2. glycogen debranching enzyme
3. phosphoglucomutase |
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Term
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Definition
| breaks alpha 1,4 linkages in the reaction: glycogen(n) + Pi --> glycogen(n+1) + glucose-1-phosphate |
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Term
| What is the rate determining step of glycogenolysis? |
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Definition
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|
Term
| From what vitamin is PLP derived? |
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Definition
|
|
Term
| What is the energy storage molecule in animal cells? |
|
Definition
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|
Term
| describe the structure of glycogen |
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Definition
| a highly branched polymer of D-glucose that branches every 8-12 residues with each branch ending in nonreducing sugar unit |
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|
Term
| How are glucose units removed from glycogen? |
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Definition
| glucose units removed sequentially from nonreducing ends; cleavage can occur on multiple branches simultaneously |
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|
Term
| 2 tissues in which glycogen is used for storage |
|
Definition
1. liver (most abundant...stored in granules)
2. skeletal muscle (energy source for movement) |
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Term
| 5 steps for making a new glycogen molecule |
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Definition
1. attach glucose to Glycogenin (Tyr residue ha OH that can form bond with glycogen)
2. Glycogenin complexes with glycogen synthase
3. glyogenin-synthase adds up to 7 more glucose residues (using the UDP-glucose substrate, Glycogenin adds glucose (NOT SYNTHASE))
4. glycogen synthase takes over once chain is > 8 residues long
5. glyogenin dissociates from synthase but remains bound to reducing end of glycogen molecule |
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Term
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Definition
| glycogen synthesis that takes place via the reaction: glycogen(n) + UDP-glucose --> glycogen(n+1) + UDP |
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Term
| 3 enzymes used for glycogenesis |
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Definition
1. UDP-glucose pyrophosphorylase
2. glycogen synthase
3. glycogen branching enzyme |
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Term
| Can glycogen synthase start from glucose? |
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Definition
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