Liver glycogen

Question 1

What is the importance of storing glycogen

Answer 1

need it in order to raise blood sugar, glucose for the brain. better source compared to protein or fat

Question 2

What is the structure of glycogen. Where in the body stores a lot of glycogen.

Answer 2

liver and muscles, its a highly branched polymer there are way more alpha 1,4 linkages than alpha 1,6.

Question 3

Glycogen has more alpha 1,6 or alpha 1,4 linkages

Answer 3

alpha 1,4 !!

Question 4

why is it beneficial for glucagon to stimulate both glcogenolysis and gluconeogenesis in liver cells?

Answer 4

both processes add sugar to the blood

liver cells have an enzyme that others don’t; they take a phosphate off the glucose and export it. once phosphate is remove the glucose is exportable. the enzyme is glucose 6 phosphatase.

Question 5

What is the reaction catalyzed by phosphoglucomutase

Answer 5

not a control point, its a step in glycogenolysis and glycogensis.

glucose 1P to glucose 6P

Question 6

How are glycogenesis and glycogenolysis are not exact reversals of one another.

Answer 6

its advantageous to not have exact enzymes,. rates are seprately controlled at each step. liver slows down one pathway while it speeds up another. more control this way

Question 7

name a compound that is the donor of glucose rings to a variety of building products.

Answer 7

UPD glucose

Question 8

hexokinase

Answer 8

phosphorylation of glucose for muscle

Question 9

glucokinase

Answer 9

phosporylation of glucose in the liver

Question 10

phosphoglucomutase

Answer 10

moves phosphate from position one to position 6,

Question 11

UDP glucose (full name)

Answer 11

uridine diphosphate UDP glucose - reaction produces fthis form glucose 1 phosphate

Question 12

describe reaction catalyzed by glycogen synthase

Answer 12

UDP glucose donates a glucose to glycogen and glycogen gets one glucose bigger. catalyzes alpha 1,4 linkages.

Question 13

describe the need for brancher enzyme

Answer 13

alpha 1,6 branching enzyme works to remodel glycogen. doesn’t make glycogen longer though

Question 14

glycogen phosphorylase

Answer 14

important for glycogenolysis. it can break the 1,4 linkage to remove a glucose. its a phosphorolysis reaction. a PPi breaks the linkage

Question 15

debrancher enzyme

Answer 15

catalyzes hydrolysis of 1,6 linkages. water breaks the linkages. small amount relative to the 1.4 linkages

Question 16

glycogen phosphorylase cofactor

Answer 16

PLP (ODD but its here)

Question 17

How is PLP formed ?

Answer 17

from B6. oxidation followed by dehydrogenase. primary alcohol oxidized to an aldehyde. then a kinase transfers a phosphate from an ATP.

Question 18

Glycogen metabolism in response to insulin signals

Answer 18

speed up, slow down glycogenolysis

Question 19

glycogen metabolism in response to glucagon

Answer 19

glycogenolysis speed up and glycogenesis slows down

Question 20

glycogen metabolism in response to epinephrine

Answer 20

glycogenolysis speed up - during exercise, think about epinephrine and how this would need to break down glycogen

Question 21

glycogen metabolism and increase in cAMP or calcium

Answer 21

glycogenolysis speeds up - think about muscle cells

Question 22

Describe regulation of glycogen metabolism by glucagon and insulin.

Answer 22

glucagon signals in the fasting state will be undone by insulin in the fed state.

if glycogen synthetase gets phosphorylated it gets inactivated. (protein kinase A which is activated during glucagon)

if glycogen phosporylase- activated

Question 23

glycogen synthase

Answer 23

make glycogen, activated with insulin

Question 24

glycogen phosphorylase

Answer 24

breaks down glycogen. activates phosphorylase kinase

Question 25

how is glycogen synthesis activated again?

Answer 25

insulin activates a protein phosphatase 1 this removes the phosphate and activates glycogen synthetase.

PP1 can catalyze dephosphorylation of many enzymes and turn on enzymes of glycogen synthesis.

Question 26

adenylate cyclase reaction

Answer 26

catalyzes ATP to cyclic AMP

Question 27

Signal transduction mechanism for epinephrine binding to a beta receptor in a liver cell

Answer 27

beta receptor is adrenergic; adenylate cyclase mechanism. its a heptahelical receptor, activates protein kinase 1

liver cells have alpha 1 receptors and beta receptors

Question 28

signal transduction for when epinephrine binds to an alpha 1 receptor

Answer 28

glycogenoysis speeds up.

• associated with another enzyme - inositol triphosphate - phospholipase C. PIP2.

Question 29

describe exercise and epinephrine and glycogenolysis

Answer 29

raising level of cyclic aMP, causes phosphorylation of glycogen phosphorylase and glycogen synthease and therefore speeds up glycogenolysis

Question 30

what is phosphorylase kinase

Answer 30

It’s a protein kinase. calcium ion will allosterically activate it. it binds to a protein called calmodulin.

only protein kinase that catalyzes phosphorylation of glycogen phosphorylase and one of the protein kinases that catalyzes phosphorylation of glycogen synthase.