Biochem Muscle Weakness Glycogen

Front 1

descriptive name for glycogen
structure of glycogen (bonds)

Back 1

branched chain homopolysaccharide made from alpha-D-gluc

alpha 1,4 glycosidic linkages
alpha 1,6 about every 8-10 glucose units

Front 2

where is glycogen stored

Back 2

cytoplasm in large hydrated granules, each containing ~100,000 gluc units
primarily in liver and muscles

Front 3

is more glycogen stored in muscle or liver

Back 3

total glycogen stored in muscle (because there is so much more muscle) is three times that of liver, even though liver has higher concentrations of glycogen

Front 4

why not store glucose in fat? or as free glucose?

Back 4

cannot convrt fat back to glucose, only glucose to fat

free glucose is osmotically active so need glycogen

Front 5

how does the function of glycogen differ in liver and muscle?

Back 5

liver maintains blod glu
muscles supply fuel reserve

Front 6

where is glycogen utilized

Back 6

75% brain, the rest is erythrocytes skeletal and heart muscles

Front 7

how long does the glycogen supply last in the liver

Back 7

less than 24 hours

Front 8

what is gluconeogenesis and why would you need glycogen if you have this pathway?

Back 8

- the synthesis of glu from small molecules like aa (happens in liver)
is much SLOWER, need fast release hence glycogen

Front 9

muscles and glycogen, why doesnt glucose diffuse out of muscles when it is made from muscle glycogen?

Back 9

muscles lack Glucose-6-phosphatase and therefore glucose found in muscles is in the G-6-P form that doesnt diffuse out of cells.

Front 10

Four broad steps of glycogen synthesis

Back 10

synthesis if UDP glucose
adding of primer
elongation
branching

Front 11

explain biochemical process of glycogen synthesis

Back 11

glucose is taken up into the cell and phosphorylated by hexokinase (glucokinase in liver)

G-6-P is then mutated to G-1-P via phosphoglucomutase

G-1-P is converted to UDP-gluc using UTP
via uridylyltransferase or UDPGLc pyrophosphorylase

Front 12

explain biochemical process of glycogen synthesis continued
use specific aa sites

Back 12

UDP-glucose is attached to glycogenin at OH of tyr 194 via autoglucosylation

glycogenin has a glucosyltransferase activity (note: udp is kicked out in the reaction)

Front 13

explain biochemical process of glycogen synthesis continued

Back 13

elongation
new glycosidic bond formed between incoming(activated) C1 OH and the accepting C4
via glycogen synthase
adds three at a time
alpha 1,4 glycosidic linkage

Front 14

what is special about glycogen synthase?

Back 14

it is rate limiting and regulated

Front 15

is glycogen synthase's Km for small glycogen molecules large or small

Back 15

it's large(ie low affinity)

Front 16

glycogen branching
enz?

Back 16

glucosyl 4:6 transferase

Front 17

how does glucosyl 4:6 transferase work

Back 17

transfers 6-8 gluc residues from end of chain to another residue forming an alpha 1,6 bond

hence its 4:6 b/c it breaks an alpha 1,4 bond and makes an alpha 1,6 bond

Front 18

is glucose added to the reducing or nonreducing end of a chain?

Back 18

non reducing

Front 19

why branch?

Back 19

increases glycogen solubility
increases nonreducing ends to which glucosyl residues can be added

Front 20

describe glycogenolysis

Back 20

glycogen phosphorylase uses Pi to cleave alpha 1,4, requires PLP (B6 derivative)as coenz

debranching enzyme: 4-alpha-D-glucotransferase, removes outer 3 of limit dextrin and attaches to a nonreducing end, amylo-alpha1,6,glucosidase cleaves last glucose

Front 21

decribe the debranching enzyme and the two catalytic sites (bifunctional)

Back 21

debranching enzyme: 4-alpha-D-glucotransferase, removes outer 3 of limit dextrin and attaches to a nonreducing end, amylo-alpha1,6,glucosidase cleaves last glucose usig water

Front 22

whats the ratio of glucoses released from phosphorylase to debranching enz

Back 22

12:1

Front 23

how else can you degrade glycogen?

Back 23

lysosomal glycogen degradation 1-3%

Front 24

REGULATION
glycogen phosphorylase is active or inactive when phosphorylated

Back 24

active when phosphorylated

a form active
b form inactive

Front 25

what activates glycogen phosphorylase
what inactivates it

Back 25

activated via phosphorylase kinase using ATP

inactivated using phosphoprotein phosphatase

Front 26

REGULATION of phosphorylase kinase
what regulates the regulator

Back 26

phosphorylated is active

phos'd by protein kinase A

dephos'd by phosphoprotein phosphatase

Front 27

glycogen phosphorylase chemical characteristics

Back 27

allosteric
T and R states,
a is active b/c P shifts equilibrium to R state

Front 28

how is PKA . . released from regulatory sites

Back 28

H activates Gprotein receptor causes formation of cAMP
cAMP binds regulatory sites on PKA and releases catalytic portion

Front 29

what does PKA inhibit and how

Back 29

phosphoprotein phostphatase

it P's protein phosphatase inhibitor activating it so that protein phosphatase cant change things back into their inactive forms

Front 30

PKA activates phosphorylase kinase which activates glycogen phosphatase releasing glucose

Back 30

jkh

Front 31

PKA inhibits phosphoprotein phosphatase by activating it's inhibitor(protein phosphatase inhibitor) so that

glycogen phosphorylase isnt turned off

Back 31

lkb

Front 32

summary of cAMP activation

Back 32

inhibits synyhesis (glycogenesis)
increases catabolism (glycogenolysis)

Front 33

cAMP

Back 33

activates glycogen phosphorylase kinase and therefore glycogen phosphorylase

inactivates glycogen synthase (because glycogen phosphorylase kinase is activated)

activates protein phosphatase inhibitor

Front 34

is glycogen synthase active or inactive when p'd

Back 34

inactive

Front 35

synthesis vs catabolism and phosphorylation

Back 35

synthesis is inactive when p'd

catab is active when p'd

Front 36

synthesis vs catabolism and phosphorylation

Back 36

synthesis is inactive when p'd

catab is active when p'd

Front 37

Insulin and glycogen synthesis

Back 37

maybe:
inhibition of protein kinases,
activation of phosphoprotein phosphatase

glycogen synthase is de P'd (active)
phosphorylase kinase and phosphorylase are de P'd (inactive)

Front 38

insulin and glycogen synthesis

Back 38

promotes
conversion of cAMP to 5'AMP

Front 39

what are allosteric effectors?

Back 39

bind enz regulatory site to promote R or T state

Front 40

what is the effector of phophorylase kinase b (catab)

Back 40

Ca, will activate this even though it's dephosed



binds delta subunit, conf change activates gamma

Front 41

what is the effector of phosphorylase b

Back 41

AMP, activates it, in muscles

Front 42

effector of phosphorylase a

Back 42

glucose, inhibits it , only hepatic

Front 43

effector of synthase b

Back 43

G-6-P, activates, in both liver and muscle

Front 44

how does Ca activate glycogenolysis in liver?

Back 44

Ca increased in liver due to epi binding alpha-adrenergic receptors

this activates phospholipase C generating IP3 and DAG
IP3 causes Ca release in cytosol which activates glycogenolysis

Front 45

AMP to ATP ratio, if increased reflects what?

Back 45

low energy

Front 46

AMP is an allosteric effector of?

Back 46

phosphorylase b, activates

Front 47

high amp to atp ratio means what

Back 47

activation of catabolism