26.1 Biochem: Glucose tolerance curves Flashcards
What is GLUT 2 for? What is its Km mean (in terms of affinity)?
For the liver/kidney etc.
Low affinity
What is GLUT 3 for? What is its Km/affinity?
Brain, high affinity (low Km)
What is GLUT 4 for? What is its Km/affinity?
Muscle and adipose tissue, less Km/affinity than brain (more than liver etc.)
What is the concentration of glucose in the hepatic portal vein? Why?
Significantly higher than in general circulation, so cells can still take up glucose despite the lower affinity of Glut2
How does glucose transport in both directions occur?
Conformational change of Glut to expose the ligand binding site
What is glucose intolerance in diabetic in part attributed to?
Impaired glucose uptake by GLUT 4
What is the difference in plasma glucose levels throughout the day in diabetics vs. non-diabeticsa?
Diabetics: always high, tends to spike after meals
Normal: fairly steadily low, slight post prandial increase
What causes Glut4 to be translocated?
PI3K phosphorylates proteins allowing Glut 4 to be translocated- a ‘key player’
What are the major organs where glycogen metabolism occurs?
Liver and kidney cortex
Where can glycogen metabolism occur under hypoxic conditions?
Astrocytes and cancer cells
What is the rate limiting step in glycogen regulation?
Glycogen synthase
Where is glucagon synthesised? When it is secreted into the blood? What type of hormone is it?
In the a-cells (pancreas)
Secreted when blood glucose drops below 4.5mmol
Peptide hormone
What are the precursors in gluconeogenesis?
Lactate, alanine and glycerol
In exercise, what is limited preventing gluconeogenesis? What do we use instead? What is a byproduct?
NAD+
Cori cycle generates glycolysis but also has lactate as a byproduct
(normally the alanine cycle allows for ATP generation)
Do muscles have glucagon receptors?
No
