Glycogen metabolism Flashcards
what is glycogenesis?
glucose –> glycogen
(anabolic)
what is glycogenolysis?
glycogen –> glucose
(catabolic)
define anabolic
builds things
define catabolic
breaks things
how does glucose get to skeletal muscles?
transported from blood by GLUT4
+activated by insulin
how does glucose get to/from liver?
transported from blood by GLUT2
which organs can store glucose as glycogen?
liver and skeletal muscles
what are glycogenolysis and glycogenesis reciprocally regulated by?
insulin and glucagon
what does glucagon signaling do to glycogenolysis and glycogenesis pathways?
glycogenolysis ON
glycogenesis OFF
what does insulin signaling do to glycogenolysis and glycogenesis pathways?
glycogenolysis OFF
glycogenesis ON
what is the reducing end vs non-reducing end of glycogen?
ONE reducing end = free -OH from C1
MANY non-reducing ends = free -OH from a different carbon
which end of glycogen are glucose molecules added / removed?
non-reducing end
what is the benefit of glycogen branching?
makes glycogen SOLUBLE
more branching = efficient glucose binding / removal at the same time for cell to use faster
what bonds are between glucose molecules on glycogen linear chain?
alpha(1,4)
what bonds are between molecules at glycogen branching points?
alpha(1,6)
3 stages of glycogenesis
- formation of UDP-glucose
- elongation
- branch formation
how is UDP-glucose made?
glucose -> glucose-6P -> glucose-1P -> UDP-glucose
(phosphate group is on C1)
what enzyme forms alpha(1,4) bonds on linear glycogen chain?
glycogen synthase
what enzyme both breaks alpha(1,4) bonds on linear chain and forms alpha(1,6) bonds at branch points on glycogen chain?
branching enzyme
how many UDP-glucose molecules does glycogen synthase add before stopping?
11
how many glucose molecules does branching enzyme cleave off and carry to make a new branch point?
6-8
how does insulin hormonally regulate glycogen synthase?
+insulin ->
activates protein phosphatase-1 ->
activates glycogen synthase
how does glucagon regulate glycogen synthase?
(only in liver- muscles don’t have glucagon receptors)
activates PKA -> inactivates glycogen synthase
what enzyme breaks alpha(1,4) bonds?
glycogen phosphorylase
what enzyme breaks alpha(1,6) bonds?
debranching enzyme
how is glycogenolysis hormonally turned OFF during fed state?
insulin -> activates protein phosphatase-1
-> inactivates both glycogen phosphorylase and its kinase (so it cant be re-activated)
what molecule is the reciprocal regulation signal for glycogenolysis and glycogenesis?
insulin
what molecule is the allosteric regulator for glycogenolysis and glycogenesis?
glucose-6P
PP-1 =
protein phosphatase-1
draw reciprocal regulation on whiteboard for insulin
draw reciprocal regulation on whiteboard for glucagon
