GNG

Question 1

LDH-5

Answer 1

Cori cycle; lactate oxidized to pyruvate; NAD+ required as cofactor

Question 2

Main substrates for GNG

Answer 2

1. Lactate from anaerobic glycolysis
2. Glucogenic a.a. (alanine & glutamate) from muscle protein breakdown
3. Glycerol derived from TAG lipolysis

Question 3

Irreversible steps in GNG (4)

Answer 3

1. Pyruvate carboxylase (mitochondrial matrix); requires Biotin (ABC)
2. PEP-carboxykinase (cytosolic); requires GTP
3. F1,6-Bisphosphatase (cytosolic)
4. G6-Phosphatase (cytosolic)

Question 4

Hepatic Glyercol Kinase fx?

Answer 4

• phosphorylates glycerol producing Glycerol-3-P
• Glycerol-3-P converted to DHAP
• No net production of glucose from the carbons of
  acetyl CoA or of fatty acids

Question 5

Role of Fructose 2,6 bisphosphate in GNG?

Answer 5

Decreased levels of F2,6-Bisphosphate decreases inhibition inhibition of FBP-1, which leads to increased rate of GNG

• Glucagon ->->->PKA-> phosphorylated PFK-2/FBP-2 (bifunctional) complex
• phosphorylated PFK-2 (INactive)/phosphorylated FBP (Active) impeding formation of F2,6-bisphosphate

Question 6

Glucose-6-Phosphatase fx?

Answer 6

In order for export of glucose to blood to occur, phosphate must be removed from G6P by glucose-6-phosphatase