Gluconeogenesis Flashcards
What is gluconeogenesis and where does it occur?
Pathway by which glucose can be made from non-carbohydrate such as amino acids, lactate, and glycerol
Occurs predominantly in the liver and some in kidney under normal conditions
Where does glycolysis mainly occur?
Brain and muscle
What three reactions in glycolysis are irreversible?
Hexokinase
PFK-1
Pyruvate kinase
What is the function of pyruvate carboxylase?
Catalyzes first reaction in gluconeogenesis
Pyruvate–>oxaloacetate
Occurs in mitochondria
What does pyruvate carboxylase require for its reaction?
Bicarbonate
Biotin
ATP
What is a strong allosteric activator of pyruvate carboxylase?
Acetyl CoA
What two things can pyruvate by made into?
Acetyl CoA
Oxaloacetate
How is oxaloacetate transported out of the mitochondria to the cytosol?
Converted to malate by a mitochondrial dehydrogenase
Malate is transported to the cytosol
Malate is converted to oxaloacetate in cytosol by dehydrogenase
What is the function of phosphoenolpyruvate carboxykinase (PEPCK)?
Converts oxaloacetate to phosphoenolpyruvate
Requires GTP
How is PEPCK regulated?
Stimulated by Glucagon
Inhibited by Insulin
What is the function of fructose 1,6-bisphosphatase-1?
Conversion of fructose 1,6-bisphosphate–>fructose-6-phosphate
Key regulatory step in gluconeogenesis
How is F1,6BPase regulated?
Activated by Citrate
Inhibited by AMP, F-2,6-BP
What is the function of PFK-2 and FBPase-2 and what is unique about these enzymes?
To form and break down F-2,6-BP, respectively
They are both part of a single protein
How does F-2,6-BP affect PFK-1?
Activates it by increasing its affinity for F-6-P
How does F-2,6-BP affect FBPase-1?
Inhibits it
What stimulates production of F-2,6-BP?
Insulin, activates PFK-2 activity, inhibits FBPase-2
What stimulates breakdown of F-2,6-BP?
Glucagon, activates FBPase-2, inhibits PFK-2
What is the function of glucose-6-phosphatase?
Catalyzes the final reaction of gluconeogenesis
Glucose-6-phosphate –> Glucose
Enzyme located in ER of liver and kidney only
What precursors can be used for gluconeogenesis?
Lactate
Glucogenic amino acids
Triacylglycerols (just backbone)
What is the Cori cycle?
Lactate generated in the muscle is transported to the liver, where it is converted to glucose.
Newly formed glucose is transported back to the muscle and used as fuel
Under what type of conditions does the Cori Cycle occur?
Anaerobic conditions
