Gluconeogenesis Flashcards
What is gluconeogenesis?
The formation of glucose from non-carbohydrate precursors
Where does gluconeogenesis occur?
Liver only
When would gluconeogenesis occur?
When blood glucose levels are extremely low
How is gluconeogenesis similar to glycolysis?
The 7 reversible steps are shared and are catalyzed by the same enzymes
How is step 1 of glycolysis bypassed in gluconeogenesis?
Glucose-6-phosphatase cuts off the phosphate with hydrolysis
How is step 3 of glycolysis bypassed in gluconeogenesis?
Fructose-1,6-bisphosphatase cuts off the phosphate with hydrolysis
Does bypassing steps 1 and 3 of glycolysis create ATP?
No, the phosphate is released as an inorganic phosphate
How is step 10 of glycolysis bypassed in gluconeogenesis?
A two step reaction. First, pyruvate carboxylase adds a CO2 to pyruvate to form oxaloacetate by using ATP hydrolysis to drive the reaction. Then PEP carboxylkinase uses a GTP to add a phosphate to oxaloacetate and cleaves off the CO2 to form PEP
Where in the cell does gluconeogenesis occur?
Bypassing step 10 occurs in the mitochondrial matrix, the rest occurs in the cytosol
What is the energy cost of gluconeogenesis?
2 NADH, 4 ATP and 2 GTP
Why is ATP and NADH invested in gluconeogenesis?
Reversing glycolysis step 6 and 7
How does fructose-2,6-bisphosphate regulate glycolysis and gluconeogenesis?
It regulates the rate limiting step in both. PFK-2 is activated by insulin, which produces F-2,6-BP. It activates PFK-1 and inhibits fructose-1,6-bisphosphatase
