Gluconeogenesis Flashcards
Describe the first regulated step of Gluconeogenesis.
Pyruvate is converted into Oxaloacetate by pyruvate carboxylase. This requires hydrolysis of an ATP. Pyruvate carboxylase is coupled to a biotin molecule for facilitation of this reaction. This step in highly up regulated by the presence of Acetyl Coa.
How is Oxaloacetate transferred outside of the mitochondria?
It is converted back to malate by the same enzyme from the CAC, where it travels outside into the cytoplasm. There it is converted back into oxaloacetate by a cytoplasmic isozyme of malate dehydrogenase.
What is biotin?
Biotin is an active form of Vitamin B7. It is required by many enzymes as a cofactor. Raw Eggs contain avidin, which has an enormously high affinity for biotin, and consumption of too many can lead to extreme inhibition of many bodily processes.
What is the second regulated step of gluconeogenesis?
Conversion of oxaloacetate to phosphoenolpyruvate(PEP) by phosphoenolpyruvate carboxykinase (PEPCK). Pyruvate -> PEP would cost 7kcal/mol, while Oxaloacetate -> PEP only cost 0.2kcal/mol
How is PEPCK regulated?
PEPCK is controlled by gene expression. Glucagon stimulates the expression of PEPCK, while Insulin inhibits its expression.
What is the third regulated step in gluconeogenesis?
Conversion of fructose-(1.,6)-bisphosphate -> Fructose-6-Phosphate by Fructose-(1,6)-bisphosphatase.
How is fructose-1,6,-bisphosphatase regulated?
fructose-1,6-bisphosphatase (FBP2) is strongly inhibited by fructose-2,6-bisphosphate, a product of PFK2. PFK2 is activated by insulin, which inhibits FBP2 (and gluconeogenesis), leading to up regulation of glycolysis. Glucagon deactivates PFK2 by way of the cAMP pathway, activating FBP2, leading to gluconeogenesis.
What are the final two steps in the gluconeogenesis pathway?
F-6-P is converted to glucose-6-phosphate, then is transported into the ER of liver or kidney cells, where glucose-6-phosphatase converts it into Glucose. It is then packaged and sent out of the cell.
What are the non-carbohydrate substrates that can be used in gluconeogenesis?
Alanine and Glutamine are deaminated and their carbon backbones are used.
Lactate can be turned into pyruvate and then to oxaloacetate.
When glycerol is released from adipose tissue, it is taken up by the liver and phosphorylated by glycerol kinase. It then enters the gluconeogenesis cycle at the point of dihydroxyacetone phosphate.
What is the Cori Cycle?
The Cori cycle refers to the cycle where glucose is converted into lactate in the muscle (through glycolysis), which then travels back to the liver, where it undergo gluconeogenesis to convert it back to glucose. It will then be sent back to the muscle to complete the cycle.
What is the function of gluconeogenesis?
To create glucose from from non-saccharide components in response to different bodily needs and signals.
