Control Of Glucose/glycogen Flashcards
Why in muscle cells is glycogen and glucose controlled
For muscle energy needs, if more energy needed glucose increases
What happens in muscle cells when exercise occurs
Increased glucose uptake into cells
Increased glycogenolysis
Decreased glycogenesis
Increased glycolysis for atp
Why does liver respond to high or low glucose eg after meal or at rest
To control blood glucose and also supply for other cells
What happens to liver cells after a meal (high glucose)
Increase glucose uptake by liver cells
Increased glycogenesis for storage
Decreased glycogenolysis
Which 3 hormones control glucose blood conc
Epinephrine
Insulin
Glucagon
Where is epinephrine produced and when is it released
Produced by chromaffin cells in the adrenal medulla
Released in emergency low glucose conc levels
Increases blood glucose
What cells does adrenaline act on for glucose increase in blood
Muscle and liver (causes contraction and also for general increase in blood)
What happens when epinephrine/adrenaline binds to GPCR on muscle or liver cells
Activates the G protein
G protein activates adenylate cyclase
ATP converted into cAMP
Camp activates PKA
PKA activates phosphorylase kinase
Activates phosphorylase A (glycogen phosphorylase) from B by phosphorylation
Phosphorylase A causes glycogenolysis (removes glucose from glycogen via phosphorylation)
What happens to glycogen synthase when glucagon or adrenaline bind
It’s inactivated (phosphorylation of it) via pKA
Stops glycogen synthesis
Where is glucagon produced
Alpha cells in the pancreas islets of langerhans
Where is insulin produced and secreted
Beta cells in pancreas
Why is it important that pancreas is highly vascularised
For glucose and o2 level sensing
Needs to secrete hormones when sensing glucose levels in blood
Where does glucagon bind to to increase BGC
Liver cells
What 4 effects does glucagon have
Decrease glucose uptake in liver cells
Increase gluconeogenesis
Increase glycogenolysis (via camp pka)
Decrease glycogenesis
Where does insulin act on when B cells detect high BGC
Liver and muscle cells receptors
How is glycogen synthase deactivated by PKA
Phosphorylation of it
What kind of receptors does insulin bind to on liver or muscle cells
RTK
Receptor tyrosine kinase (enzyme linked receptors)
How is glycogen phosphorylase A activated by PKA
Addition of a phosphate
Explain how insulin causes glycogenesis when bound to RTK
Causes auto phosphorylation on the receptor domains
IRS becomes phosphorylated
Activates Protein kinases
PK inactivate glycogen synthase kinases (by phosphorylation)
This activates glycogen synthase because glycogen synthase kinase no longer phosphorylates glycogen synthase
= active glycogen synthase
Which enzyme keeps glycogen synthase phosphorylated (inactive) which is then inactivated by insulin binding
Glycogen synthase kinase
What is IRS
Insulin receptor substrate
Why does glucose need glut uniporters for transport
It’s hydrophilic
Which GLUT receptor channels are found on all cells
Glut 1 and 3
Where is glut 2 found
Liver and pancreas
Why is GLUt2 important at the Bcells in pancreas
It regulates the release of insulin
Explain the steps of what happens when high glucose levels flow into Bcells down glut2 receptor channel
Causes glycolysis within the B cell
Releases ATP
ATP is used to block K+ channels
This causes depolarisation which causes ca2+ channels to open
Ca2+ flooding into Bcell causes insulin release
Why is glut 2 important in liver cells
Allows uptake of glucose when too high in blood
Where is GLUT 4 located and controlled by
In fat (adipose) cells and muscle cells
Controlled by insulin
How does insulin binding to muscle cells cause uptake of glucose
When insulin binds to muscle cells it causes glut 4 transporters to be released from the recycling endosome
They are embedded into the plasma membrane for glucose uptake into muscles when exercise is high
What is type 1 diabetes caused by
Insulin deficiency
Autoimmune attack on Bcells so insulin can’t be released
What do type 1 diabetics rely on
Insulin injection
What was type 2 thought to be caused by first
Increased insulin in the blood due to food intake
Caused peripheral resistance to insulin in liver and muscle cells
Glucose levels can’t decrease
Apart from peripheral resistance of liver and muscle cells to insulin, what else was thought to cause diabetes
B cell death due to exhaustion from continuous insulin release
What was found recently to cause diabetes 2 which now shows it is reversible
Beta cell hiding to avoid death
B cells hide from the lipids and fat which overspill from the liver
B cells therefore hide from the lipids and aren’t active
How can diet reverse diabetes 2
B cells stop hiding from the overspill of fats and lipids
Because of the inability of diabetics to store glucose as glycogen, what happens
Renal excretion of glucose form the kidneys in urine , the reabsorption channels become saturated with glucose
Causes water loss in urine too due to high osmolarity in the blood (high glucose)
