glycogen synthesis and regulation

Question 1

glycogen synthesis

Answer 1

glucose-> glucose-6-phosphate by HEXOKINASE/GLUCOKINASE(LIVER)
glucose-6-phosphate-> glucose-1-phosphate by
PHOSPHOGLUCOMUTASE
glucose-1-phosphate + UTP-> UDP-glucose + PPi
TRANSFERASE
UDP-glucose + glycogenin-> glycogen + UDP
GLYCOGEN SYNTHASE/BRANCHING ENZYME

Question 2

Activation of glycogen synthase

Answer 2

glycogen synthase b (P)-> a by PROTEIN PHOSPHATASE
glycogen synthase a-> b(P) by PROTEIN KINASE A using ATP
A is active form

Question 3

glycogen breakdown

Answer 3

glycogen-> glucose-1-phosphate
GLYCOGEN PHOSPHORYLASE/DEBRANCHING ENZYME
glucose-1-phosphate-> glucose-6-phosphate
MUTASE ENZYME
glucose-6-phosphate-> glucose (liver) OR glycolysis

Question 4

glycogen phosphorylase activation

Answer 4

a (P)-> b protein phosphatase
b-> a (P) protein kinase a using ATP
A is active form

Question 5

what activates PKA and protein phosphatase

Answer 5

PKA: glucagon + adrenaline

protein phosphatase: insulin

Question 6

camp pathway to glycogen phosphorylase a

Answer 6

camp activates PKA -> activates glycogen phosphorylase kinase -> activates glycogen phosphorylase a

Question 7

how else is glycogen content regulated in the liver

Answer 7

when glucose is high, it binds to glycogen phosphorylase-> inactivation -> less glycogen breakdown

Question 8

how else is glycogen content regulated in muscle by ca

Answer 8

during muscular contraction, ca is released from SR
ca binds to calmodulin of glycogen phosphorylase kinase, activating it-> glycogen phosphorylase gets a phosphate, activating it-> increased glycogen breakdown

Question 9

how else is glycogen content regulated in muscle by ATP/AMP

Answer 9

during exercise, atp drops and amp rises
amp is an allosteric activator of glycogen phosphorylase
atp is an allosteric inhibitor of glycogen phosphorylase