Gluconeogenisis Flashcards
Where & when does gluconeogenisis occur?
Occurs mainly in the liver and kidney in both the cytosol and mitochondria, and usually during fasted states.
Can skeletal muscle perform gluconeogenesis & why?
No, due to the absence of Glucose-6-Phosphatase
What would be a good way of conceptualizing gluconeogenesis with regard to glycolysis?
Basically glycolysis in reverse with the exception of 3 irreversible steps that have alternate pathways in gluconeogenisis.
What is the first step of gluconeogenesis?
Converting Pyruvate to Oxaloacetate
What enzyme converts Pyruvate into Oxaloacetate?
Pyruvate Carboxylase
How is Pyruvate converted into Oxaloacetate?
Shuttled into the Mitochondria through specific carrier proteins, then interacts with CO2, ATP, and the gluconeogenic enzyme: pyruvate caboxylase to become Oxaloacetate.
Within the first step of gluconeogenesis, Oxaloacetate is further converted into what?
Phosphoenolpyruvate (PEP)
Where does Oxaloacetate interact with Phosphoenolpyruvate Carboxykinase?
In the Cytoplasm.
What enzyme converts Oxaloacetate into Phosphoenolpyruvate?
Phosphoenolpyruvate Carboxykinase
When the enzyme Phosphoenolpyruvate reacts with Oxaloacetate, what acts as the electron donor & what is liberated from the reaction?
GTP acts as the electron donor
CO2 is liberated back.
What is the second step of gluconeogenesis?
Converting Fructose-1,6-Bisphosphate into Fructose-6-Phosphate
How is Phosphoenolpyruvate able to convert into Fructose-1,6-Bisphosphate?
It is a reversible reaction of glycolysis.
What enzyme converts Fructose-1,6-Bisphosphate into Fructose-6-Phosphate?
Fructose-1,6-Bisphosphatase
What is the third step of gluconeogenesis?
Converting Glucose-6-Phosphate into Glucose.
What enzyme is converts Glucose-6-Phosphate into Glucose?
Glucose-6-Phosphatase
Phosphatase enzymes do what?
They are the enzymes that break the phosphate bond.
What is the rate limiting step of gluconeogenisis?
Fructose-1,6-Bisphosphate to Fructose-6-Phosphate
What is Fructose-1,6-Bisphosphatase activated by?
Citrate
What is Fructose-1,6-Bisphosphatase inhibited by?
AMP & Fructose-2,6-Bisphosphate
What activates Pyruvate Carboxylase?
Acetyl CoA
What is the “big picture” regulator of gluconeogenisis & why?
Glucagon
Glycolysis happens in response to insulin < > Glucagon inhibits glycolysis & promotes gluconeogenisis.
What is an acronym to remember the metabolic steps specific to gluconeogenesis?
P
O
P
F
F
G
G
What hormone stimulates gluconeogenesis?
Glucagon
