T2 L6: Liver Homeostasis Flashcards
What are the 3 main energy sources for ATP synthesis?
Glucose, long chain fatty acids, and amino acids
What are long chain fatty acids stored as?
Triglycerides
Where are the fuels for energy synthesis stored?
In the liver and adipose tissues
What are 4 reasons why cerebral cells are so sensitive to hypoglycaemia?
- They derive their energy from aerobic respiration
- They can’t store glucose in significant amounts or synthesise glucose
- They can’t metabolise substrates others than glucose or ketone bodies
- Glucose entry into the brain is not facilitated by hormones so it’s limited
What is gluconeogenesis and where does it occur?
It’s synthesis of glucose from non-carbohydrate precursors like amino acids, glycerol, and lactate in the liver or kidneys
What is glycogenolysis and where does it occur?
It’s the metabolism of liver glycogen stores
What is glycolysis and where does it occur?
It’]s the oxidation of glucose by peripheral tissues
At what range is plasma glucose maintained at?
2.5 - 8 mM
When is dietary glucose the main source of blood glucose?
When glucose is being absorbed from the small intestine (2-3 hours following a meal)
How long do glycogen stores last?
12-24 hours
Which pancreatic cells secrete glucagon?
Alpha cell
Which pancreatic cells secrete insulin?
Beta cells
Where are Glut 1 transporters found?
Erythrocytes, muscles, brain, kidneys, colon, placenta, and foetal tissue
Where are Glut 2 transporters found?
Liver and pancreatic Beta cells
Where are Glut 3 transporters found?
Brain
Where are Glut 4 transporters found?
Skeletal muscles and adipose tissue
Which Glut transporter is sensitive to glucose?
Glut 4
Where are Glut 5 transporters found?
Small intestine (fructose transporter)
What are some properties of Glut 1 glucose transporters? Their affinity?
They are responsible to basal glucose uptake and decrease in glucose deprivation. Affinity = 1mM
What are some properties of Glut 2 glucose transporters? Their affinity?
Have a high capacity, low affinity of 15-20 mM. Takes up glucose only at very high [glucose] and conserves it for other tissues
What are some properties of Glut 3 glucose transporters? Their affinity?
They are predominantly neuronal and supply tissues with high energy demands. High affinity of 1 mM irrespective of [blood glucose]
What are some properties of Glut 4 glucose transporters? Their affinity?
Affinity = 5 mM. Found on insulin sensitive tissues
How do Glut 4 glucose transporters work?
They are found in cell cytosol so when insulin binds to a receptor, cell signalling occurs which translocates Glut 4 into the membrane. Then Glut 4 can transport glucose
What are some properties of cellular effects of insulin?
- occur within minutes
- don’t require protein synthesis
- occur in very low [insulin]
