BGM1002/L26 Control of Glucose & Glycogen Metabolism Flashcards
What happens to glycogen metabolism in muscles during exercise?
Increased glycolysis
Increased glucose uptake
Increased glycogen breakdown
Decreased glycogen synthesis
What happens to glycogen metabolism in muscles at rest?
Decreased glycolysis
Decreased glucose uptake
Decreased glycogen breakdown
Increased glycogen synthesis
What happens to glycogen metabolism in the liver after a meal?
Decreased glucose release
Decreased glycogen breakdown
Increased glycogen synthesis
What happens to glycogen metabolism in the liver during fasting/exercise?
Increased glucose release
Increased glycogen breakdown
Decreased glycogen synthesis
What 3 key hormones regulate glycogen metabolism?
Epinephrine
Glucagon
Insulin
Where is epinephrine released from?
Adrenal medulla
Where are glucagon and insulin released from?
Pancreas
What mechanism does epinephrine act through to affect glycogen metabolism?
G-protein linked receptors
What cascade of events does epinephrine cause in glycogen metabolism?
cAMP-dependent phosphorylation cascade
Where does epinephrine act to affect glycogen metabolism?
Muscle and liver
What hormone is secreted by beta cells?
Insulin
What hormone is released by alpha cells?
Glucagon
What other kinds of cells does the pancreas contain?
Delta cells (somatostatin), PP cells and others
Why is the pancreas highly vascularised?
For glucose sensing and high O2/nutrient demand
What percentage by mass of the pancreas are islet cells?
What percentage blood flow of the pancreas do they require?
1-2% mass
10-15% blood supply
What tissue does glucagon act on?
Liver
What tissues does insulin act on?
Liver and muscle cells
Adipose tissue
Name 2 key enzymes in control of glycogen metabolism.
Glycogen phosphorylase
Glycogen synthase
How is glycogen phosphorylase activated?
Phosphorylation
How is glycogen synthase activated?
Removal of phosphate group
Which 2 key hormones in glycogen metabolism act via G-protein linked receptor?
Glucagon and epinephrine
By what mechanism does insulin work?
Via a receptor tyrosine kinase
How many isoforms of GLUT transporters exist?
16
Where are GLUT1 and GLUT3 found?
All mammalian tissues
Where are GLUT2 found?
Liver and pancreatic beta-cells
What is the Km of GLUT1 and GLUT3 transporters?
1mM
What is the Km of GLUT2 transporters?
15-20mM
What is the role of GLUT2 transporters in (a) the liver and (b) in the pancreas?
(a) removes excess glucose from blood
(b) regulation of insulin
When blood glucose is high, how do GLUT2 transporters mediate insulin secretion? (5)
Glucose enters cell
Glycolysis occurs
Ca2+ activated
Ca2+ enter cell
Insulin secreted
How does insulin affect transport of GLUT4 transporters?
Insulin stimulates transport of GLUT4 to plasma membrane in muscle and adipose cells
What is the Km of GLUT4 transporters?
5mM
How can number of insulin receptors be increased in muscle?
Endurance training
What is type 1 diabetes mellitus?
Absolute insulin deficiency due to beta-cell destruction
How is type 1 diabetes mellitus treated?
Exogenous insulin injection, pancreas/islet transplant
Give 2 potential future treatments for type 1 diabetes mellitus.
Xenotransplantation, iPS/ePS stem cells, immunomodulation
Name the 2 stages that type 2 diabetes WAS considered to have.
1 - hypeinsulinemia/beta cell compensation/peripheral insulin resistance
2 - insulin deficiency caused by beta-cell death
Give the revised progression of type 2 diabetes.
1 - no change
2 - beta-cell ‘hideaway’ to avoid cell death
What occurs during hyperglycaemia to cause polydipsia?
Glucose enters renal filtrate
Glucose reabsorption saturated
Water follows by osmosis
Large volume of urine
