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27 Cards in this Set
- Front
- Back
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what specific bond is associated with branching on a glycogen molecule?
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alpha-1,6-glycosidic bond
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branching on a glycogen molecule occurs at approximately every ______ glucose monomers.
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8 to 14
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in the first step of glycogen synthesis, glucose-1-P goes to UDP-glucose via what enzyme and cofactor?
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UDP-glucose pyrophosphorylase and UTP
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are the 2 Phosphates on UDP-glucose both from UTP?
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No, one is from UTP and the other remains from glucose-1-P.
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what, self-glycosylating, protein forms the initial glucose monomer chain from which glycogen can be formed?
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Glycogenin
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what enzyme acts to add UDP-glucose to the growing glycogen chain?
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glycogen synthase
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is UDP-glucose added to the non-reducing or reducing end of the glycogen template?
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non-reducing end
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what action the the 'branching enzyme' perform? be specific
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-a 7 segment section is transferred from the non-reducing endof a chain to the C6-hydroxyl group on the same or another glycogen molecule.
-every segment transferred comes from a chain at least 11 residues long. -branching point must be at least 4 residues from all other branches |
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In regards to glycogen degredation, what are the yeilded percentages of glucose-1-P to free glucose?
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90% G-1-P to 10% free glucose
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wat is the action of 'glycogen phosphorylase'?
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-causes the cleavage of alpha-1,4-linked residues yeilding G-1-P + Gly(n-1).
-continues cleavage until at least 5 residues from a branching point. |
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what is the mechanism of action of the 'debranching enzyme'?
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-first, the enzyme transfers the last three residues on the branch chain to the non-reducing end of another glycogen molecule.
-then, the enzyme cleaves the alpha-1,6-glycosidic linkage to yeild free glucose + debranched glycogen. |
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How many active sites does the 'debranching enzyme' have?
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2 active sites
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what are the allosteric effectors of 'glycogen phosphorylase'? how do they effect the enzyme?
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activator: AMP, (phosphorylation)
inhibitors: ATP, Glucose-6-P, free glucose. |
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what are the allosteric effectors of 'glycogen synthase'? how do they effect the enzyme?
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activators: ATP, liver glucose, gucose-6-P.
inhibitor: (phosphorylation) |
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glucogon binds to a cell surface receptor protein which is a member of a group of proteins called, _____.
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G-proteins
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the G-protein receptor of glucagon activates what enzyme?
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adenylate cyclase
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adenylate cyclase aids in the synthesis of what molecule?
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cyclic-AMP
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what group of proteins does cAMP phosphorylate and activate?
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"cAMP dependant protein kinases"
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cAMP dependant protain kinases phosphorylate and activate what two enzymes?
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phosphorylase kinase and PPI-1 (phosphoprotein phosphatase inhibitor-1)
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'phosphorylase kinase' phosphorylates what two enymes with what effect?
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glycogen synthase (inactivates)
glycogen phosphorylase (activates) |
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what two effects do the actions of action of phsphorylase kinase have which together have an additive effect.
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it activates glycogen degredation at the same tome as it inhibits gycogen synthesis.
-this ensures a unidirectional path. |
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Ca+ inds to what subunit of the phosphorylase kinase enzyme? what affect does this have?
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binds to 'calmodulin' subunit. results in increased enzyme activity.
(binding of AMP also causes increased activity...) |
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what glucose transporter is activated by insulin? where is it present? how is it stored?
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GLUT-4. present in muscle and adipose tissue. stored in intracellular vesicles.
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what two effects does insulin binding to muscle cells have on the glucose transporter GLUT-4?
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stimulates its release from intracellular vesicles and also INCREASES its Vmax.
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what effect does insulin binding have on 'phosphodiesterase'? what does this enzyme do?
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activates phosphodiesterase which in turn degrades cAMP.
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what effect does insulin have on 'phosphoprotein phosphatase-1 (PP-1)? what does this enzyme do?
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activates the enzyme which leads to the Dephosphorylation of: phosphorylase kinase, glycogen synthase, glycogen phosphorylase and PPI-1
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which enzyme of gluconeogenesis is effected by insulin? how?
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insulin leads to the inactivation of PEPCK.
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