lecture 3: glycogen, glycolysis Flashcards
what protein is located at the centre of the glycogen
glycogenin
what is it and what is the function of glycogenin
is it a protein backbone
acts as an anchor for the glucose monors to eveually attach and form glycogen
what branches off the glycogenin
glycogen branches!!
is the glycogen only linear>?
no it is like a tree with linear and then branching segments
what is responsible for breaking the glucose branches
branching enzymes
where is glycogen stored and what is the purpose
stores in muscle and liver for energy storage for future use (exercise, rest, starvation)
what are the 2 main bonds of the glycogen?
alpha 1-4 glycosidic bonds
alpha 1-6 glycosidic bonds
which bonds are responsible for the linear portion of glucose
aplha 1-4 glycosidic
which bonds are responsible for the branching part of glycogen
1-6 glycocidic bonds
what does 1-4 mean or 1-6
there is a bond between the 1first carbon of a glucose and the 4 or 6 carbons of a different glucose which are bound by an oxygen molecule
after how many glucose monomers do we get an 1-6 bond
5-8
why is branching important
allows you to utilize many glucose monomers at once
what is a strand of glycogen made up of
glucose monomers bound together
true or false: glycogen is made up solely of reducing ends
no , made up of reducing and non reducing ends
what are the two types of ends to the glycogen
reducing
non reducing
which ends are sensitive to glycogen phosphorylase
non reducing ends
what happens at the non reducing ends
sensitive to glycogen phosphorylase
this is where you can either build up or break down the glycogen
(these are the first glucose monomers to be cleaved for energy)
what is the purpose of glycogen phosphorylase
breats down glycogen
(breaks away glucose monomers from he glycogen tree to go down the glycolotic pathway
what is the function of glycogen synthase
to synthesize glycogen
true or false: a main branch of glucose forms from the glycoenin protein
true
what are the reducing ends of glycogen
the ends where there is no synthesis or breakdown of the glycogen tree
(these are the ends that are connected to glycogen)
does the glycogen phosphorylase cleve off 1 or multiple glucose monomers at once
one at a time, very rapidly
explain how glycogen phosphorate works
cleaves the monomers off at the non reducing end
uses inorganic phosphate to attach to that glucose
beomces glucose 1 phosphate and then that can go to glycolysis
what does the breakdown/activation of the glycogen depend on
intensity of exercise
what are the 4 enzymes involved in branching and debranching as well as storage/breakdown linearly?
1-6 bonds:
branching and debranching enzymes
1-4:
glycogen synthase and glycogen phosphorylase
what is the function of the branching enzyme of glycogen
branching enzyme creates the 1-6 glycosidic bonds (branch)
what is the function of the debranching enzyme
debranching cleaves/breaks the 1-6 bond
do the branching and debraching enzymes work at the non reducing ends
no thats for the 1-4 bonds only
what stimulates the glycogen synthase and the branching enzyme (the creation of more glycogen) and what is the function
insulin
allows us to store glycogen for future energy use
what are the 2 main functions insulin
allows glucsoe uptake in the cell
stimulates glycogen synthase and branching enzyme
is insulin (synthase and branching) important for glycogenesis or glycogenolysis
glycogenesis
are glycogen phosphorylase and debranching important for glycogenesis or glycogenolysis
glycogenolysis
where is insulin located
can be found in liver and muscles (secreted by beta cells of liver)
what are the 3 stimulators of glycogen phosphorylase (glycogenolysis)
epinephrine
glucagon
AMP
what are the two HORMONES that stimulate glycogenolysis
glucagon
epinephrine
what is the product stimulator of glycogenolysis
AMP
explain how glucagon is a stimulator
Glucagon is stimulated by the alhpa cells in the pancreas during exercise to signal the breakdown of the glycogen for glucose
where is glucagon found
liver
explain how epinephrine is a stimulator of glycogenolysis
when exercise is high, in the liver and in the muscle, stimulated to breakdown glycogen for energy
is the relationship between exercise intensity and stimulators directly proportional or indirectly
directly
as energy increases
hormone secretion increases
where is epinephrine found
liver and muscle cells
where is the AMP stimulator found
muscle
explain how AMP is a stimulator for glycogenolysis
During high intensity exercise, AMP will begin to accumulate in the cell
When AMP is present, the cell knows there is a low energy source so it stimualtes glycogen phosloryza and debraching enzymes
true or false: glycogenolysis and glycogenesis are supposed to happen at the same time
false, do not want these systems workign at the same time (coutner productuve)
what are the two forms of glycogen phosphorylase
phosphorylase a (active) phosphoralase b(inactive)
explain active vs inaction phosphorlaze
when there is a phophosphate bound to the glucogen phosphorylase, it is activated and will stimulate the breakdown of glycogen
when the phosphate group is removed, you get glycogen phosphorylase b (inactive) which will inhibit glycogenolysis
what inhibits the glycogen synthase
when a phosphate group is added to glycogen synthase, it is inhibited and cannot do glycogenesis
what happens at the same time that glycogen phosphorylase is activated
when the enzyme for glycogenolysis is activated (has a phosphate group attached), the enzyme for glycogenesis (glycogen synthase) is INHIBITED by phosphorylation
what is an example of a futile system
glycogenolysis and glycogenesis
what is the protein/kinase that allows this activation/inhibition of the two systems at the same time
c (cyclic amp) dependent protein kinase
do epinephrine and glucagon enter the cell to directly activate glycogenolysis
no , they simulate CAMP dependent protein kinase
what is the function of Camp depending on protein kinase?
Activates glycogen phosphorylase (glycogenolysis) by adding an inorganic phosphate to the enzyme
AT THE SAME TIME
inhibits glycogen synthase (glycogenesis) by adding an inorganic phosphate to the enzyme
who is the main contributor for the activation and inhibition of glycogenolysis and glycogenesis
C-amp depending protein kinase
what is the breakdown of glycogen dependent on
exercise intensity (ie. light exercise=less rate of breakdown/ glycogenlosys)
where is epinephrine/adrenaline released from
adrenale glands (adrenal medula)
explain glycogen utilization during exercise
light exercsie: almost have 100% of glycogen content left (very light rate of glycogen breakdwon)
moderate: over a 2 hour period, there is a graducal reduction of glyocgen from the msucle fibers doing the work
heavy exercise: wont be able to exercise for long ebcause you will breakdown all the glycogen content
what happens when the the glycogen content is at almost 0% in your muscles
muscles are fatigued because the myofibirls are almost totally depeleted of glycogen
what are the two options for glucose 6 phosphate
1) glycogen synthesis
2) glycolysis
what are the first 4 steps of glycolysis and the energy requirements
Glucose > glucose 6 phosphate (1 ATP needed)
Glucose 6 phophate >frucose 6 phosphate (no energy)
fructose 6 phosphate> frcose 1,6 dispohoate (1 ATP NEEDED)
fructise 1-6 diphosphates splits
2 atp deficit
what happens once fructose 1-6 diphosphate is formed
the 6 carbon molecule will split into two 3 carbon entities
when is atp start to be synthesized in glycolysis
after it splits into the 2 3 carbon units
when is the first 2 atp manufactured in glycolysis
1-3 diphosphoglyceric acid to
3 phosphoglyceric acid
when is the last 2 atp’s being made in glycolysis
phospholenulpyruvic > pyruvate
ADP>ATP by losing a phosphate
what is the final product of glycolysis
2 pyruvic acids (pyruvate)
what is the net energy yield of glycolysis
2 atp
