Glycogen Flashcards
glycogen is a polymer of
glucose
what is the main glycogen storage organ
liver
most glycogen disorders stem from what kind of abnormalities
liver
what allows the body energy in their storage for 24 hours
glucose and glycogen storage
what storage allows the body to survive for several weeks
triacylglycerol
will maternal glucose cross placenta to enter baby
yes
describe glycogen storage and a fetus/newborn
during the last few weeks, the baby will turn glucose into glycogen and store it in the liver.
describe what happens once baby is born regarding glucose/glycogen
when baby is born they are no longer receiving glucose through placenta, so glucose levels drop. this stimulates glycogenolysis
what happens to baby if mother is anorexic regarding glycogen
they will not have enough glycogen stored and will likely become hypoglycemic within their first few hours of birth
what is glycogen made out of
lots of glucose
what is the linkage of glucose in glycogen
α1,4 & α1, 6
describe the significance of the structure of glycogen
osmotic effects reduced
insoluble but reactive
how much glycogen is stored in liver
it varies with food intake. after eating more will be stored
glycogen in liver is used to buffer
blood plasma
if fasting when will glycogen in liver run out
12-24 hours
draw out glycogen in muscle pathway
pg 6
draw out glycogen in liver pathway
pg 6
is there glycogen in heart? explain
a little. there is a lot in purkinje conductors
is muscle glycogen affected by fasting
no
What does UDP G stand for
UDP glucose
UDP G is synthesized from
glucose 1 phosphate
UDP G is branch point for
glycogen synthesis
and other pathways
glycogen synthesis is catalyzed by what enzyme
by glycogen synthase and the branching enzyme.
glycogen degradation is catalyzed by what enzyme
glycogen phosphorylase and a debrancher enzyme
what is function of glucose 6 phosphatase
generates free glucose from G6P
what enzyme controls the interconverstion of glucose 6 phosphate and glucose 1 phosphate
phosphoglucomutase
what is the affect of galactose-1-phosphate uridyl transferase deficiency
hypoglycemia (glycogen metabolism is altered)
glycogen accumulation in liver
what is another name for glycogenin
Tyrosine-glycosyl transferase
how does the early fetus make glycogen when it has 0 glycogen
it forms the primer through glycogenin which autophosphorylates and self glucosylates
what kind of bond does glycogen synthase create
α1,4
where is glycgen synthase expressed
liver and muscle
where does glycogen synthase add add’l glycogen
adds additions at non reducing (OH) end
how is glycogen synthase shut off
phosphorylated
where is glycogen synthase phosphorylated
serine residue
each glycogen chain has how many residues
12-14
what enzyme allows branching to happen in glycogen
glycogen-branching enzyme (also called amylo (1→4) to (16) transglycosylase, or glycosyl-(4→6) transferase
draw out the glycogen synthase activation and inactivatino pathway
pg 12
top right
GSK3 requires priming by what
casein kinase
what activates PP1
insulin
glucose 6 phosphate
glucose
what inactivates PP1
glucagon
epinephrine
insulin signaling pathway increases what enzymes in muscle
hexokinase
glycogen synthase
what is functino of glycogen synthase
makes glycogen for energy storage
what is ultimately increasing the flux toward glycogen, esp in muscle
insulin affect on hexokinase
glucose transport in muscle is mediated by
GLUT4
exercise will increase what transporter
GLUT4
impaired glucose transport in skeletal muscle leads to what
contriutes to type 2 diabetes mellitus
cortisol induces
glycogen synthesis
draw the glucose to glycogen pathway
pg 16
describe the action of glycogen phosphorylase
removes single glucose residues by breaking α1, 4 linkages
name two advantages of glycogen phosphorylase and how it works through phorphorylating step
.The glucose is removed from glycogen is an activated state, i.e. phosphorylated and this occurs without ATP hydrolysis.
2.The concentration of Piin the cell is high enough to drive the equilibrium of the reaction in the favorable direction since the free energy change of the standard state reaction is positive.
what is pyridoxal phosphate
vitamin B6
what does PLP stand for
Pyridoxal phosphate
50% of body’s PLP is bound to
glycogen phosphorylase
glycogen phosphorylase cannot remove glucose from
α1, 6 branches
what is needed to remove the glucose connected by α1, 6 branches
glycogen debranching enzyme (GDE)
what does GDE stand for
glycogen debranching enzyme
what is the official name of GDE
amylo-1,6-glucosidase, 4-α-glucanotransferase
describe the action of GDE
cleaves three glucose residues and transfers them to nonreducing endo f chain
cleaves the remainder α1,6 glucose and it becomes free glucose
draw out the pathway of epinephrine and Ca2+ in glycogen degradation
pg 20
epinephrine and Ca2+ oppose control of
synthase & phosphorylase
what activates glycogen synthase
glucose 6 P
what inactivates glycogen phosphorylase
Glucose 6P
ATP
Glucose
Ca2+ in muscle promotes
glucose production & glycogen degradation
what are the activators of breakdown of glycogen in muscle
Ca2+
AMP
what are the inhibitors of glycogen breakdown in muscle
ATP
G6P
what are the synthesis of glycogen activators in muscle
G6P
what are the two states of glycogen phosphorylase
T or R
what state can glycogen phosphorylase bind glycogen
R state
R state of glycogen phosphorylase is enhanced byq
AMP
R state of glycogen phosphorylase is inhibited by
ATP
G6P
when fasting, what is main source of blood glucose in first 12-24 hours
glycogen degradation
after 24 hours of fasting what is main source of blood glucose
gluconeogenesis
if PFK1 is mutated what glycogen storage disease results
GSD VII - Tarui
why does mutation of PFK1 cause a glycogen storage disease
If PFK1 is mutated, that means there is accumulation of G6P
G6P inhibits glycogen phosphorylase
glycogen phosphorylase is responsible for degradation of glycogen
what is other name of GSD4
Anderson
what kind of defiency is GSD4
branching enzyme deficiency in liver and muscle
what is deficienct in GSD4
Transglucosidase
how does GSD4 present
hepato-splenomegaly
muscle and liver structure damaged b/c branching of glycogen damaged
retardation
dead within 3 years common
GSD5 stands for
McArdle
where is deficiency in GSD5?
myoglycogen phosphorylase deficiency
describe how pt with GSD5 presents
exercise intolerance
what causes myoglycogen phosphorylase deficiency
genetic defect in phosphorylase (this affects breakdown of glycogen)
GSD2 what is other name
Pompe
GSD2 is due to
acidic α glucosidase deficiency
describe what is happening in GSD2
lysosomal defect. body can’t get rid of glycogen, it accumulates. will have enlarged heart, floppy baby. usually die around 9 months
what two mutations can cause von gierke disease
lack of glucose 6 phosphatase
translocase
describe von gierke disease and why pt is not well
if there is no glucose 6 phosphatase, free glucose can’t be released from liver. → severe fasting hypoglycemia
increased G6P = increased PPP & increased glycolysis to pyruvate
more lactate production b/c more pyruvate
more Acetyl CoA b/c more pyruvate = more fatty acid synthesis
b/c there is more glycolysis → more glycerol 3 phosphate → triglyceride synthesis, hyperlipidemia
hepatomegaly, cirrohis
GSD0 explain
it is not true GSD
glycogen synthase deficiency
what are symptoms of GSD0
hypoglycemia lethargy pallor nausea vomiting sometimes seizures before breakfast
what relieves hypoglycemia in pts with GSD0
protein rich meals
uncooked corn starch before bed
what are the normal glucose levels for baby
3.3-10
what are low glucose levels of baby after birth
1.5-less than 10
why can’t glucagon signal myocyte?
myocyte doesn’t have receptors for glucagon
draw epinephrine & glucagon pathway
pg 19, left pic
draw epinephrine and glucagon covalent siganling control
pg 19 right pic
what will nitric oxide to to BP
decrease
what is the job of glycogen in cardiac muscle?
to produce oxaloacetate
how does the cardiac cell producing oxaloacetate help it to make energy?
it increases capacity of TCA
where is pyruate converted to oxaloacetate in cardiac muscle
mitochondria
how does oxaloacetate help TCA cycle
Increases capacity of TCA cycle to process Acetyl CoA.
what does glucose do to glycogen phosphorylase
exposes the phosphates so that insulin can come and take them off and inactivate
what does insulin do to glycogen phosphorylase
removes the phosphates, inactivating it
describe the symptoms of von gierke’s disease
pg 35
in the liver, what happens to blood while fasting
glucagon increases
insulin decreases
in liver, what happens to tissue while fasting
cAMP increases
glycogen degradation increases
glycogen synthesis decreases
in liver, what happens to blood after carbohydrate meal
glucagon decreases
insulin increases
in liver, what happens to tissue after carbohydrate meal
cAMP decreases
glucose increases
glycogen degradation decreases
glycogen synthesis increases
in liver what happens to blood during exercise and stress
epinephrine increases
in liver, what happens to tissue during exercise and stress
IP3 increases
Ca2+ calmodulin increases
glycogen degradation increases
glycogen synthesis decreases
in muscle, what happens to blood while fasting (rest)
insulin decreases
in muscle, what happens to tissue while fasting (rest)
glycogen synthesis decreases
glucose transport decreases
in muscle, what happens to blood after carbohydrate meal while at rest
insulin increases
in muscle, what happens to tissue after carbohydrate meal while at rest
glycogen synthesis increases
glucose transport increases
in muscle what happens to blood during exercise
epinephrine increases
in muscle, what happens to tissue during exercise
AMP increases Ca2+ calmodulin increases cAMP increases glycogen degradation increases glycolysis increases
