Term
| stages of glycogen breakdown |
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Definition
1. release glucose as glucose-1-phosphate
2. remodel glycogen
3. convert G-1-P into G-6-P |
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Term
| enzyme to release glucose (G-1-P) |
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Definition
| glycogen phosphorylase. removes glucose units sequentially from non reducing end using phosphorolysis. |
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Term
| enzyme to remodel glycogen |
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Definition
| debranching enzyme: transferase moves 3 residues from branch to another nonreducing end. glucosidase hydrolyses 1,6 bond releasing glucose. |
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Term
| enzyme to convert G-1 to G-6-P |
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Definition
| phosphoglucomutase. intramolecular transfer: has a BISPHOSPHATE intermediate |
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Term
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Definition
| break bond by inserting phosphate. active site excludes water to prevent competition. it is used to release G-1-P, which is easier/ takes less energy to process into G-6-P compared to glucose (product of hydrolysis) |
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Term
| stages of glycogen synthesis |
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Definition
1. activation of G-1-P by UDP-glucose.
2. addition of glucose to nonreducing ends of glycogen.
3. Branching enzyme to add alpha-1,6 linkages |
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Term
| G-1-P for synthesis comes from |
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Definition
| G-6-P. phosphoglucomutase is a reversible reaction. |
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Term
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Definition
| equivalent to ATP. adds to glucose to get acitvated UPD-glucose and PPi |
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Term
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Definition
only found in the liver
G-6-P + H20 -> glucose + Pi
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Term
| UDP-glucose pyrophosphorylase |
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Definition
G-1-P + uridine triphosphate (UTP) -> UDP-glucose + PPi
- reaction is readily reversible, but PPi is rapidly hydrolysed in vivo to orthophosphate
- that rxn is irreversible.
- reaction is driven forward by low conc of PPi
- many biosynthetic rxns are driven in this way
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Term
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Definition
active, phosphorylated form.
favors the R state.
was activated by phosphorylase kinase at serine residue
active regardless of levels of AMP, ATP, or G-6-P |
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Term
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Definition
inactive, non-phosphorylated form.
favors the T state.
phosphorylase kinase converts it to phos. a
in normal conditions, ATP and G-6-P keep phos. b inactive
elevated levels of AMP during excersise activate phos. b |
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