Chapter 24 - Glycogen Breakdown

Front 1

Where is glycogen stored and what is it used for in those areas?

which area has a higher conc of glycogen?

Back 1

liver - glycogen for glucose in bloodstrean
muscle - glycogen undergoes glycolysis for energy required by muscle

liver higher conc

Front 2

What is the structure of glycogen

Back 2

a 1,4 links
a 1,6 branch

Front 3

Branches are at every --- glucose residue

Back 3

10

Front 4

glycogen less/more energy rich than fatty acids

glycogen is a good source for what kind of activity?

the released glucose from glycogen can provide energy in the absence of ---. fatty acids can not do this!

glycogen is a supply of energy for ANAEROBIC /AEROBIC ACTIVITY

Back 4

less

sudden, strenuous activity

oxygen,

glycogen is a supply of energy for ANAEROBIC ACTIVITY

Front 5

Glycogen is in the ---- present as large intracellular ----

Back 5

cytoplasm, granules

Front 6

The efficient breakdown of glycogen to provide ----- for further metabolism requires four enzyme activities: one to ---- glycogen, two to ---- glycogen so that it remains a substrate for degradation, and one to ----t the product of glycogen breakdown into a form suitable for further metabolism.
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Back 6

G6P

degrade, remodel, covert

Front 7

1st step of glycogen breakdown

Back 7

glycogen --glycogen phosphorylase--> Glucose 1 phosphate
phosphorylytic cleavage
Pi splits the glycosidic linkage between c1 and c4

Front 8

Glycogen phosphorylase works on ---- ends

Back 8

non reducing (-OH, hydroxyl)

Front 9

Why phosphorolysis and not hydrolysis?

Back 9

glucose is already phosphorylate, no burning of tap, trapped inside muscle cell bc no transporter for g1p (neg charge).

The phosphorolytic cleavage of glycogen is energetically advantageous because the released sugar is already phosphorylated. In contrast, a hydrolytic cleavage would yield glucose, which would then have to be phosphorylated at the expense of a molecule of ATP to enter the glycolytic pathway.

Front 10

second step of glycogen breakdown?

Back 10

g1p --phosphoglucomutase-->g6p

Front 11

the reaction catalyzed by phosphoglucomutase.

A -- group is transferred from a --- residue of the enzyme to the substrate at carbon --- (-OH), and a different ---- group from carbon --- is transferred back to restore the enzyme to its initial state.

Back 11

phoshoryl, serine, phosphoryl

C6, C1

Front 12

whats another enzyme similar to phosphoglucomutase? what residue does it use to transfer phosphate to g1p?

Back 12

phosphoglyceratemutase

histidine!

Front 13

phosphorylase can not proceed if a l,4 linkage is --- glucose residues away from a branching point

what enzyme is used then? what does it do?

Back 13

4


transferase, shifts 3 glucose residues from the branch to the main chain.

Front 14

what is the other part of transferase that hydrolyzes that last branch residue?

Back 14

a 1,6 glucosidase

Front 15

what is the debranching enzyme?

Back 15

a- 1,6 glucosidase

Front 16

deficiency is trans+a1,6 glucosidase leads to what disease?

Back 16

cori's

Front 17

a l,6 glucosidase release --- through hydrolyzation

Back 17

GLUCOSE

this is a minor fraction of glucose produced from glycogen break down

Front 18

g6p --> glucose. what enzyme

absent in liver or muscle?

Back 18

g6phosphatase
absent in muscle
muscle use it directly

glucose is able to leave organ

Front 19

g6phosphatase generates what 2 things?

Back 19

glucose and orthphosphate (Pi)

Front 20

two forms of glycogen phosphorylase?
which is more active/

Back 20

phosphorylase a - MORE ACTIVE
phosphorylase b

Front 21

PHOSPHORYLASE IS phosphorylated on --- 14 of each sub unit. favors -- state

Back 21

SERINE, R (RELAXED) +active

Front 22

PHOSPHORYLASE NONACTIVE FORM IS PHOSPHORYLASE -- AND I IN -- STATE

Back 22

B, T (TENSE)

Front 23

When phosphorylase b in t state transition to a and r state is controlled by what


what are neg allosteric regulators that stabilize the t state and keeps it there?

what are the positive allosteric regulators that stabilize r (active state) / phosphorylase a?

--- bind phos b and turns it to phos a

Back 23

energy charge

ATP, GLUCOSE - high energy state

AMP - indicates low nrg state of cell which glucose production is needed so need to breakdown glycogen

amp - allosteric binding

Front 24

phosphorylase b --> phosphorylase a by what enzyme

Back 24

phosphorylated by phosphorylase kinase

Front 25

phosphorylase kinase is activated by what hormone---

Back 25

epinerphrine

phosp. phosphorylase b in muscle

Front 26

phosphorylase a has no ---- effectors like phosphorylase b

Back 26

allosteric

. In contrast, phosphorylase a is fully active, regardless of the levels of AMP, ATP, and glucose 6-phosphate.

Front 27

conformation change in T state shift the ---- domains is proximity of --- site.

Back 27

regulatory, active

Front 28

in liver, what binds to phos a and deactivates it?

Back 28

glucose

Front 29

unlike the enzyme in muscle liver phosphorylase in insensitive to regulation by --- bc the liver does no undergo dramatic changes in nrg state

Back 29

amp

Front 30

in liver, --- signals a fed state and dephosphorylates the a form

Back 30

insulin

Front 31

in liver, --- signals a starved state and cause phosphorylation of b -->a by --

Back 31

glucagon

phosphorylase kinase

Front 32

Phosphorylase kinase ia a multisubunit complex and is partly activated by ----- of its --- subunits by ---.

also partly activated by ----which binds to it delta subunit which is composed of?

what is required for full activaation of phosphorylase in liver?

Back 32

phosphorylation, beta, pka


Ca2+, calmodulin

ca2+ binding and pka phosphorylation

Front 33

what triggers Ca2+?
pka?

Back 33

hormones, muscle contraction, nerve impulses


hormones

Front 34

what activates PKA?
through what cascade?

Back 34

liver glucagon
(fasting)

muscle epinephrine (flight or fight)
cAMP cascade

Front 35

epinephrine binds beta/alpha-adregenic receptor on what cells.

glucagon binds to what cells

explain the epinephrine cascade in muscle / glucagon in liver

Back 35

BETA

muscle and liver

liver only (bind to glucagon receptor)

epinephrine -> receptor -> cAMP -> PKA -> phosphorylase kinase -> turns phosphorylase b into a

Front 36

explain epinephrine binding in liver cells

what kind of receptor? beta or alpha adregenic?

Back 36

it triggers phosphoinositide cascade

epinephrine ---> bind 7tm - alpha betaadregenic! --> activates phospholipase c cleaves pips to --> ip3 and DAG --> ip3 mind to receptor on er membrane --> release calcium

alpha (beta in muscle)

Front 37

What else is effected by PKA?

Back 37

FBPase 2 activated, glycolysis is inhibited, gluconeogenesis is stimulated.

fbpase 2 turns f 2,6 bp --> f6p for gluconeogenesis

remember fbpase 2 phosphorylates pfk2 (enzyme in glycolysis)

Front 38

How is PKA signaling turned off?

Back 38

PP1

Front 39

PP1 inactivates both --- -- and --- --- by ----

---- synthesis is then activated

Back 39

phosphorylase kinase
glycogen phosphorylase
dephosphorylation

glycogen

Front 40

signal transduction shut down

no -- present

--- activity of g protein turn off

--- convert cAMP to AMP

Back 40

hormones
GTPase
phosphodieterase