1.12 Glycogen Metabolism Flashcards
Glycogen is degraded by removal of a terminal glucose from where?
the nonreducing end of a glycogen chain
Where is Glycogen mostly stored
In liver and muscle
What enzyme degrades the terminal glucose from the glycogen chain
Glycogen Phosphorylase
Glycogen metabolism is demonstrative of a hydrolysis or a phosphorolysis?
Phosphorolysis
At what point on the Glycogen chain does the enzyme stop removing terminal glucose molecules?
On the fourth residue from the branch point
After Glucose molecule is released from Glycogen chain, what structure is it?
Glucose 1-Phosphate
What enzyme converts Glucose 1-phosphate to Glucose 6-phosphate?
Phosphoglucomutase
What activates and prepares Glucose 1-phosphate to be added to the glycogen chain?
The activation and attachment of a sugar nucleotide
Ex: G1P + UTP –> UDP-Glucose
What enzyme catalyzes the addition of a sugar nucleotide to G1P
UDP-glucose pyrophosphorylase
What enzyme catalyzes the first step of glycogen synthese by converting G6P to G1P
Phosphoglucomutase
What enzyme catalyzes the addition of the glycosyl unit to the glycogen chain?
Glycogen Synthase
What happens to UDP during the addition of the glycosyl unit to the terminal end of the glycogen chain
It is displaced by the terminal Hydroxyl group of the growing glycogen molecule
T or F, The glycosyl residues can only be added to the glycogen chain if it already contains 4 residues
True
How is a branch made during Glycogen synthesis
Breaking of an alpha 1-4 link of a block of about six or seven glycosyl residues from the terminal nonreducing end. This block is transfered to a more interior residue on the C-6
What enzyme catalyzes the alpha 1-6 linkages found at branching sites
branching enzyme Glycosyl (4-6) transferase
Role of Glycogenin
Acts as a primer for new branches of glycogen. Since glycogen synthase can only add to chains of 4 residues, this enzyme makes those first four residues attach so that glycogen synthase can act
What is the only enzyme that is common to both glycogen synthesis and metabolism
Phosphoglucomutase
T or F, Glycogen synthesis and breakdown are reciprocally regulated, stimulation of one inhibits the other
True
Glycogen Phosphorylase is phosphorylated to form a, what occurs?
This is the active form of glycogen phosphorylase and triggers glycogen breakdown
Phosphorylase a is dephosphorylated or phosphorylated?
Phosphorylated
Glycogen Synthase a is dephosphorylated or phosphorylated?
Dephosphorylated
When glycogen synthase a is dephosphorylated, what is triggered?
Glycogen Synthesis
