Glycogen metabolism

Question 1

where do you find most glycogen stores

Answer 1

cytosol of liver and skeletal muscle

Question 2

how is glucose linked

Answer 2

alpha 1,4-glucosidic bond in the main and branched alpha 1,6 linkages

Question 3

what happens to glucose arising from glycogen breakdown in skeletal and heart muscles

Answer 3

remains in the muscle cells and is used to provide energy for muscle work

Question 4

occurs during fasting and is stimulated by glucagon in liver

Answer 4

glycogenolysis

Question 5

after a meal what enzymes are active

Answer 5

glycogen synthase and 4:6 transferase (branching enzyme)

Question 6

during fasting what enzymes are active

Answer 6

debrancher enzyme and glycogen phophorylase

Question 7

insulin is up, glycogen synthesis active or inactive

Answer 7

active

Question 8

how is futile (energy wasting) controlled during glycogen synthesis

Answer 8

breakdown and formation are not active at same time

Question 9

glycogen synthesis requires

Answer 9

ATP and UTP

Question 10

Glucose 1-P and UTP synthesize

Answer 10

UDP-glucose

Question 11

UDP-glucose adds glucosyl residues to glycogen core (glycogenin) by

Answer 11

glycogen synthase

Question 12

reattaches 6-8 residues in alpha-1,6-bond after chain reaches about 11 residues in length

Answer 12

branching enzyme

Question 13

glycogen synthesis and glycogenolysis are regulated by

Answer 13

hormonal changes (insulin and glucagon)

Question 14

key regulatory enzyme for degradation?

Answer 14

glycogen phosphorylase

Question 15

during fasting _____ elevates in liver

Answer 15

glucagon

Question 16

during exercise, _____ and ____ elevate

Answer 16

AMP and epinephrine

Question 17

____ are partially degraded during exercise or fasting

Answer 17

glycogen molecules

Question 18

glycogen phosphorylase catalyzes the cleavage of ______ bond releasing ______

Answer 18

alpha 1,4 glycosidic bond releasing glucose 1-P

Question 19

hydrolyzes alpha 1,6 glycosidic bond

Answer 19

debranching enzyme

Question 20

glucose 1-P converted to ______ and catabolized for energy in muscle

Answer 20

Glucose 6-P

Question 21

In liver what happens to glucose 1-P

Answer 21

converted to glucose 6-P then to glucose by glucose 6-phosphatase and released from the liver as free glucose

Question 22

glucose 6-phosphatase is found where

Answer 22

liver cell’s lumen of ER

Question 23

muscle cells do not need to convert ____ to glucose for usage

Answer 23

glucose 6-P

Question 24

liver glycogenesis inhibitors and activators include

Answer 24

- = glucagon, epinephrine, and Ca 2+
\+ = insulin, glucose 6-P

Question 25

liver glycogenolysis inhibitors and activators

Answer 25

``` - = glucose, insulin, glucose 6-P, ATP + = glucagon, epinephrine, Ca2+ ```

Question 26

muscle glycogenesis inhibitors and activators

Answer 26

``` - = epinephrine + = insulin, Glc 6-P ```

Question 27

muscle glycogenolysis inhibitors and activators

Answer 27

``` - = insulin, Glc-6P, ATP + = epinephrine, AMP, Ca2+ ```

Question 28

insulin binds to what enzyme to dephosphorylate

Answer 28

protein phosphatase 1 (PP1)

Question 29

activation of PP1 does what in general and does what to glycogen synthase and phophorylase

Answer 29

dephosphorylates | activates glycogen synthase and inactivates glycogen phosphorylase

Question 30

glucagon only affects

Answer 30

liver

Question 31

Glucagon does what in liver cells

Answer 31

1. binds G protein coupled receptors on hepatocytes 2. cAMP from glucagon activated adenylate cyclase increases protein kinase A activity (PKA) 3. PKA phosphorylates glycogen synthase making it inactive and phosphorylates glycogen phosphorylase making it active

Question 32

muscle glycogen degradation increased with

Answer 32

exercise and epinephrine signaling

Question 33

exercise activates muscle glycogenolysis how?

Answer 33

1. muscle contration that produces AMP which is activator of glycogen phosphorylase 2. nerve signal which increase Ca2+ which binds calmodulin which activates phosphorylase kinase 3. epinephrine through PKA activates same phosphorylase kinase

Question 34

exercise results in:

Answer 34

active glycogen phosphorylase

Question 35

does epinephrine signaling initiate liver glycogen degradation?

Answer 35

yes

Question 36

epinephrine binds to what in hepatocytes and what occurs

Answer 36

alpha1 adrenergic receptors which are Q's which activate phospholipase C

Question 37

how does phospholipase C do its job?

Answer 37

1. hydrolyzes PIP2 to DAG and IP3. 2. IP3 stimulates release of Ca2+ form ER 3. Ca2+ binds to calmodulin which activates calmodulin-dependent protein kinase and phosphorylase kinase (both Ca2+ and DAG activate PKC) 4. these 3 kinases phosphorylate glycogen synthase making it inactive. Phosphorylase kinase phosphorylates glycogen phosphorylase making it active

Question 38

how does neonatal hypoglycemia become relevant

Answer 38

mother is uncontrolled diabetic

Question 39

who is at most risk for life threatening hypoglycemia?

Answer 39

babies that are born prematurely

Question 40

fetal exposure to high levels of glucose results in

Answer 40

high glycogen stores and increased insulin levels in fetus

Question 41

______ may develop life threatening hypoglycemia with new borns

Answer 41

hyperinsulinemia

Question 42

GSD 1 is called what and what happens with it

Answer 42

von Gierke disease glucose 6-P severe fasting hypoglycemia, lactic acidosis, hyperuricemia, increase in FA/cholesterol by increase in glucagon signal

Question 43

GSD 2 is called what and what happens with it

Answer 43

Pompe disease Lysosomal alpha glucosidase leads to cardiac failure and myopathy

Question 44

GSD 3 is called what and what happens with it

Answer 44

Cori disease issue with amylo-1,6-glucosidase (debrancher) ketolytic hypoglycemia, increase in beta oxidation. glycogen deposits have short outer branches

Question 45

GSD 4 is called what and what happens with it

Answer 45

Anderson disease issue with amylo-4,6-glucosidase (brancher) hepatosplenomegaly

Question 46

GSD 5 is called what and what happens with it

Answer 46

McArdle disease (muscle) muscle glycogen phosphorylase exercise induced muscle pains, cramps, and weakness

Question 47

GSD 6 is called what and what happens with it

Answer 47

Hers disease (hepatocyte) liver glycogen phosphorylase hepatomegaly, good prognosis

Question 48

Pompe disease involves what organ(s)

Answer 48

all organs with lysosomes

Question 49

von Gierke disease involves what organ(s)

Answer 49

liver

Question 50

Andersens disease involves what organ(s)

Answer 50

liver

Question 51

Cori disease involves what organ(s)

Answer 51

liver, skeletal muscle, heart

Question 52

McArdle disease involves what organ(s)

Answer 52

skeletal muscle

Question 53

Hers disease involves what organ(s)

Answer 53

liver (hepatocytes)