Glycogen metabolism

Question 1

what is glycogenesis?

Answer 1

glucose –> glycogen
(anabolic)

Question 2

what is glycogenolysis?

Answer 2

glycogen –> glucose
(catabolic)

Question 3

define anabolic

Answer 3

builds things

Question 4

define catabolic

Answer 4

breaks things

Question 5

how does glucose get to skeletal muscles?

Answer 5

transported from blood by GLUT4

+activated by insulin

Question 6

how does glucose get to/from liver?

Answer 6

transported from blood by GLUT2

Question 7

which organs can store glucose as glycogen?

Answer 7

liver and skeletal muscles

Question 8

what are glycogenolysis and glycogenesis reciprocally regulated by?

Answer 8

insulin and glucagon

Question 9

what does glucagon signaling do to glycogenolysis and glycogenesis pathways?

Answer 9

glycogenolysis ON
glycogenesis OFF

Question 10

what does insulin signaling do to glycogenolysis and glycogenesis pathways?

Answer 10

glycogenolysis OFF
glycogenesis ON

Question 11

what is the reducing end vs non-reducing end of glycogen?

Answer 11

ONE reducing end = free -OH from C1

MANY non-reducing ends = free -OH from a different carbon

Question 12

which end of glycogen are glucose molecules added / removed?

Answer 12

non-reducing end

Question 13

what is the benefit of glycogen branching?

Answer 13

makes glycogen SOLUBLE

more branching = efficient glucose binding / removal at the same time for cell to use faster

Question 14

what bonds are between glucose molecules on glycogen linear chain?

Answer 14

alpha(1,4)

Question 15

what bonds are between molecules at glycogen branching points?

Answer 15

alpha(1,6)

Question 16

3 stages of glycogenesis

Answer 16

1. formation of UDP-glucose
2. elongation
3. branch formation

Question 17

how is UDP-glucose made?

Answer 17

glucose -> glucose-6P -> glucose-1P -> UDP-glucose

(phosphate group is on C1)

Question 18

what enzyme forms alpha(1,4) bonds on linear glycogen chain?

Answer 18

glycogen synthase

Question 19

what enzyme both breaks alpha(1,4) bonds on linear chain and forms alpha(1,6) bonds at branch points on glycogen chain?

Answer 19

branching enzyme

Question 20

how many UDP-glucose molecules does glycogen synthase add before stopping?

Answer 20

11

Question 21

how many glucose molecules does branching enzyme cleave off and carry to make a new branch point?

Answer 21

6-8

Question 22

how does insulin hormonally regulate glycogen synthase?

Answer 22

+insulin ->
activates protein phosphatase-1 ->
activates glycogen synthase

Question 23

how does glucagon regulate glycogen synthase?

Answer 23

(only in liver- muscles don’t have glucagon receptors)

activates PKA -> inactivates glycogen synthase

Question 24

what enzyme breaks alpha(1,4) bonds?

Answer 24

glycogen phosphorylase

Question 25

what enzyme breaks alpha(1,6) bonds?

Answer 25

debranching enzyme

Question 26

how is glycogenolysis hormonally turned OFF during fed state?

Answer 26

insulin -> activates protein phosphatase-1 -> inactivates both glycogen phosphorylase and its kinase (so it cant be re-activated)

Question 27

what molecule is the reciprocal regulation signal for glycogenolysis and glycogenesis?

Answer 27

insulin

Question 28

what molecule is the allosteric regulator for glycogenolysis and glycogenesis?

Answer 28

glucose-6P

Question 29

PP-1 =

Answer 29

protein phosphatase-1

Question 30

draw reciprocal regulation on whiteboard for insulin

Question 31

draw reciprocal regulation on whiteboard for glucagon