Glycogen breakdown Flashcards
what other types of fuels are present when we don’t have carbs
proteins form our muscles
triglycerol from our diet or from adipose tissue
what is PROTEIN broken down into
amino acids
what is triacylglycerol broken down into
fatty acids
what do we do if our body is in a starved state
want to breathe-by engaging muscles
how is protein used as a fuel
broken down into amino acids
then into ammonia and then incorporated into the urea cycle
how else can acetyl coa be made
from fatty acids and amino acids
what type of fuel does our brain and some cells with no mitochondria use
only glucose
how is protein converted into glucose
broken down into amino acids
converted into CoenzymeA
converted into pyruvate
converted into glucose
how is triacylglycerol converted to glucose
broken down into glycerol and then glucose
can fatty acids be converted into glucose
NO
what is stored in the muscles
glycogen
what is glycogen used for
used as fuel on demand
where is glycogen stored
in muscles or in the liver
what happens to the glycogen stored in the liver
it is used for glycogen derived glucose for the pentose phosphate pathway
what happens during fight or flight
the liver also mobilises its glycogen stores and releases glucose for use by muscles
what happens after prolonged fasting
glycogen reserves will be used up and the metabolism needs to start synthesising glucose from non carbohydrates to maintain levels
what is it called when glucose is made from non carbohydrates
gluconeognesis
how long is prolonged fasting
more than 24 hours
what is necessary for human life
a constant supply of blood glucose
what is the energy source for exercising muscles
glucose- it is the substrate for anaerobic respiration
how do we get glucose
diet intake
make glucose- gluconeogensis
degredation of glycogen
why is glucose from diet intake not the best
not always readily available and is sporadic
when is glucose mobilised from glycogen
between meals or during exercise
describe glycogen
excellent short term storage source which when required can be accessed and used immediately
what is the molecular mass of one molecule of glycogen
10^8 daltons
where is glycogen stored
in discrete cytoplasmic granules which contain most of the enzymes necessary for glycogen synthesis and degradation
describe glycogen
homopolysaccharide made from only a D GLUCOSE
multiple chains and highly branched
which bonds are found in glycogen
a 1,4 glycosidic bonding and 1,6 glycosidic bonding found at the branches
where does glycogen branches occur
8-10 glucosyl residues
what is the significance of branching
glycogen is synthesised and broken down by adding or removing glucose units from NON REDUCING ENDS
what does branching create
countless non reducing ends which means glycogen can be synthesised or broken down rapidly
what is the main function of liver glycogen
maintenance of blood glucose between meals and during early stages of fasting
what is the main function of muscle glycogen
fuel reserve for muscle contraction
is the glucose released from the glycogen exportable in the liver
is released into the blood to be used by other tissues
is the glucose released from the glycogen exportable in the muscle
cannot leave the muscle it enters glycolysis
what is the size of glycogen stores in liver
10% wet weight of liver-stores lasts about 24 hrs
what is the size of glycogen stores in muscle
1-2% of wet weight of muscle but we have more muscle than liver
what is the hormonal control of glycogen in the liver
glucagon and adrenaline promote breakdown
insulin promotes synthesis
what is the hormonal control of glycogen in the muscle
adrenaline promotes breakdown
insulin promotes synthesis
when is glycogen broken down
from non reducing terminals when blood glucose begins to fall( in liver only)
when muscles need glucose for ATP(broken down in muscles and liver)
how is glycogen broke down
glycogen (n residues) + Pi with the enzyme glycogen phosphorylase to form glucose 1 phosphate and glycogen( n-1 residues)
when might glycogen phosphorylase be defective
defective in type V glycogen storage disease(effects muscle)
what hormones does the liver respond to
glucagon and adrenaline
what hormones does the muscle respond to
adrenaline ONLY
describe phosphorylated glucose
much more energy rich molecule can glucose
when does glycogen phosphorylase stop cleaving
stops 4 units to the branch point
which enzymes do we need to cleave at the branch point
- transferase- cuts three units off and attaches to the long chain
- amylo- a 1,6 glucosidase
what does transferase do
it cuts three units off the branch and attaches to the long chain
what does amylo-alpha 1,6 glucosidase do
hydrolyses the last glucose unit and attaches it to the long chain and then glucose phosphorylase can work again
what is the ratio of glycogen breakdown
generates mainly glucose 1 phosphate along with some glucose( 8:1)
what is the pathway of glycogen breakdown in the liver
- broken down into glucose 1 phosphate(8) and glucose(1)
- converted into glucose 6 phosphate by phosphoglucomutase- reversible reaction
- glucose 6 phosphate dephosphorylated into glucose by glucose 6 phosphatase with hydrolysis
- glucose released into blood to maintain glucose levels
what is the pathway of glycogen breakdown in the muscle
- glucose 1 phosphate (8) and glucose(1) rpdocued by breakdown of glycogen
- the small amount go glucose is converted into glucose 6 phosphate by hexokinase using ATP
- the glucose 1 phosphate is converted into glucose 6 phosphate by phosphoglucomutase
- glycolysis in the muscle generates ATP
- the muscle doesn’t have glucose 6 phosphatase and cannot convert glucose 6 phosphate INTO GLUCOSE. trapped in the muscle for glycolysis
what is produced in the pentose phosphate pathway
ribose and NADPH
how do we regulate the glycogen metabolism
controlled by hormones
allosteric control regulates glycogen metabolism
give an example of allosteric control of glycogen metabolism
amp allosterically stimulates glycogen breakdown while ATP inhibits glycogen breakdown
what does adrenaline and and glucagon do in the liver
stimulates muscle glycogen breakdown ready for fight or flight
what does glucagon do
signals low blood glucose but muscles ignores this as muscle serves glycogen for its own needs
how does the hormone signalling work
1.adrenaline works in muscle and liver
2.glucagon only works in liver
3.binding of the hormones leads to activation of adenylate cyclase
4.catalyses formation of cAMP from ATP
5.activates protein kinase A ( in the cytosol)
6.the catalytic site phosphorylates phosphorylase kinase
7.phosphorylase kinase phosphorylates glycogen phosphorylase
8. we then get glycogen breakdown
this is regulated by glycogen synthase( inactive) which can be activated by protein kinase A
when is phosphorylase kinase most active
in the presence of PKA
or when muscles are contracted ( high levels of calcium ions present)
what is the hormonal control of glucagon and adrenaline known as
an amplification cascade
when is insulin released
when blood glucose is elevated( after a meal) and stimulates glycogen synthesis whilst inhibiting breakdown
how does the hormone signalling work
1.adrenaline works in muscle and liver
2.glucagon only works in liver
3.binding of the hormones leads to activation of adenylate cyclase
4.catalyses formation of cAMP from ATP
5.activates protein kinase A ( in the cytosol)
6.the catalytic site phosphorylates phosphorylase kinase
7.phosphorylase kinase phosphorylates glycogen phosphorylase
8. we then get glycogen breakdown
this is regulated by glycogen synthase( inactive) which can be activated by protein kinase A
what else does active phosphoprotein phosphatase 1 do
hydrolyses glycogen phosphorylase a( active) into glycogen phosphorylase b( inactive)
glycogen switched off
what is the hormonal control of glucagon and adrenaline known as
an amplification cascade
what tissue is affected in von gierkes disease
liver
intestine
kidney
what tissue is affected in pompe disease
liver muscle heart
what tissue is affected in forbes disease
liver muscle
due to abnormal glycogen structure
what tissue is affected by andersen disease
liver
abnormal glycogen structure
what tissue is affected in McArdlie disease
muscle only
what tissue is affected in pompe disease
liver muscle heart
what tissue is affected in forbes disease
liver muscle
due to abnormal glycogen structure
what tissue is affected by andersen disease
liver
abnormal glycogen structure
what tissue is affected in McArdlie disease
muscle only
what enzyme is defected in von gierke disease
glucose 6 phosphatase
what enzyme is defected in pompe disease
lysosomal a glucosidase
what enzyme is defected in forbes disease
amylo 1,6 glucosidase
what enzyme is defected in andersen disease
1,4 a glucan branching enzyme
what enzyme is defected in McArdlie disease
phosphorylase
what tissue do we need for diagnosis of von gierkes disease
liver
what tissue do we need for diagnosis of pompe disease
leukocytes
liver
muscle
what tissue do we need for diagnosis of forbes disease
leukocytes
liver
muscle
what tissue do we need for diagnosis of andersen disease
leukocytes
liver
muscle
what tissue do we need for diagnosis of McArdlie disease
muscle
what is the outcome for patients with McArdle disease
normal lifespan exercise must be avoided
what is NASH
non alcoholic steatohepatitis-
what is the outcome for patients with forbes disease
good prognosis
what is the outcome for patients with andersen disease
death in first 3 years
what are the symptoms of NASH
silent or non specific making it difficult to diagnose- remain unaware till late stages of the disease
what is NASH
non alcoholic steatohepatitis-
describe NASH
defined as liver manifestation fo metabolic disorder and most severe form of non alcoholic fatty liver disease
what else might people suffer with if they have NASH
obesity
pre diabetic
diabetes
what are the symptoms of NASH
silent or non specific making it difficult to diagnose
