Gluconeogenesis Hormonal Regulation

So we know the liver's role is to maintain blood-glucose levels. It does this by using fructose-2,6-Bisphosphate. 

• Reminder: This is NOT the same thing as Fructose-1,6-Bisphosphate, and actually is not involved in glycolysis or gluconeogenesis at all, besides its ability to activate or inhibit enzymes. 

Which enzymes!? 

It STIMULATES phosphofructokinase but INHIBITS fructose-1,6-bisphosphatase 

Concept check:

What does this tell you about when the liver would want to make fructose-2,6-bisphosphate? 

(A. It would want to make fructose-2,6-bisphosphate when it wants to undergo glycolysis and NOT undergo gluconeogenesis. → phosphofructokinase is stimulated, which will catalyze the step towards generating pyruvate in glycolysis, and will inhibit fructose-1,6-bisphosphate from generating glucose)  → Insulin will activate F-2,6-BP synthesis 

What generates F-2,6-BP? 

PFK-2

Again, it is not the same thing as PFK (phosphofructokinase). This enzyme has 2 functional domains that make and break down F-2,6-BP. 

• Note: Think of the liver as being “self-less” → it stops producing sugar when glucose levels are low. 

Cori Cycle: this cycle illustrates how the liver and muscle cells work together. 

→ Lactate produced by the muscles during contraction goes into the blood, the liver removes them and converts it into glucose, which is again released into the blood.