module 5- glycogen metabolism Flashcards
what enzyme connects glycogen metabolism with PPP, glycolysis & gluconeogenesis?
glucose 6-P
T or F: glycogen is a large, branched polymer of glucose
T
what is the key regulatory enzyme in glycogen synthesis?
glycogen synthase
2 ways glycogen phosphorylase is regulated?
allosterically interactions & reversible phosphorylation
what 2 enzymes signal the need for glycogen breakdown?
epinephrine & glucagon
glycogen synthase & glycogen degradation are ( ) regulated?
reciprocally
what is glycogenin
protein, where glycogen synthase begins
T or F: branched structure increases rate of glycogen synthesis & degradation
T
what are the 2 linkages responsible for branching
a-1,4 & a-1,6
how many ATP are needed per 1 glucose molecule for glycogen synthesis?
2 ATP
how many ATP are produced for every 1 glucose 6-P oxidized during glycogen degradation
31
what is the % of storage efficiency of glycogen
94%
what is glycogen synthesis pathway called
glycogenesis
what type of glucose is used in glycogenesis
activated form - called UDP-glucose
UDP-glucose function
adds glucose units to glycogen
Is UDP-glucose used in glycogen breakdown?
No
what is the glycogen degradation pathway called?
glycogenolysis
T or F: glucose itself is not the substrate for glycogenesis but UDP-glucose is used as activated precursors
T
mutases function
change position of phosphate group
glycogen synthesis converts….
glucose -> glycogen
glycogen degradation converts…
glycogen -> glucose
where is glucose added to the glucose chain & what type of bond does it form?
adds to terminal glucose (C4) to form a-1,4 glycosidic bond
how does a glycogen molecule get started?
glycogenin acts as both catalyst & substrate
oligiosacchardie is primer
what enzyme catalyzes formation of a-1,6 bond?
the branching enzyme
how many residues apart between a-1,6 bonds?
8-12
how many glucose units can 1 glycogen have?
30,000
what enzyme extends both non-reducing ends followed by more branching?
glycogen synthase
what is the key regulatory enzyme in glycogen synthesis
glycogen synthase
what enzyme is a strong allosteric activator of glycogen synthase
glucose 6-P
phosphorylase A is ( ) form and is ( )
active, phosphorylated
phosphorylase B is ( ) form and is ( )
inactive, dephosphorylated
main enzyme that degrades glycogen
glycogen phosphorylase
glycogen synthase is active in ( ) form and phosphorylase is active in ( )
unphosphorylated, phosphorylated
what enzyme interconverts glucose 6-P and glucose 1-P
phosphoglucomutase
T or F: glycogen phosphorylase can only cleave a-1,4 bonds
T
T or F: the debranching enzyme releases free glucose
T
products of the reaction catalyzed by glycogen phosphorylase
glucose 1-P & glycogen molecule that is 1 glucose molecule shorter
fates of glucose 6-P in the liver vs muscle
liver- free glucose is produced & enters blood
muscle- used by muscles to metabolize energy
glycogen storage depletes in ( ) during exercise
1 hour
what is glycogen supercompensation
glycogen amounts are doubled
what tissue/organ is glycogen phosphorylase b sensitive to allosteric modifiers in?
muscle
when is epinephrine secreted? vs when is glucagon secreted?
E-when quick energy burst is needed
G- secreted by the pancreas in response to low blood sugar
glycogen storage diseases is caused by?
lack of glucose 6-P = unable to release glucose = build up
when you eat, glucose levels ( ) which causes insulin ( ) and be stored as glycogen
increase, release
T or F: glycogen synthase & glycogen phosphorylase are both regulated by cAMP signalling system
T
What enzyme converts glycogen phosphorylase A to B
Phosphatase
What enzyme converts glycogen phosphorylase B to A
Kinase
6 steps of regulatory cascade
- Binding of hormone to receptor
- Adenylate cyclase activated
- cAMP production increases
- PKA activation
- Glycogen phosphorylase is phosphorylase
- Stimulation of gluconeogenesis
Phosphorylase & glycogen synthase become phosphorylated in response to
Glucagon or epinephrine
What metabolic pathway does PP1 inhibit?
Glycogenolysis (degradation)
Insulin binds to receptor and causes what
Phosphorylation of 2nd messenger
