Gluconeogenesis Flashcards
What is the function of the Glucose-Alanine Cycle?
Pyruvate produced in the muscles is converted to Alanine. Alanine can carry toxic NH3 to the liver. In the liver, NH3 enters into the urea cycle and alanine is reconverted to pyruvate for gluconeogenesis.
What molecule stimulates PFK1, but inhibits the Fructose-1,6-bisphosphotase in gluconeogenesis?
Fructose-2,6-bisphosphate
What enzyme is used in the reversible reaction to form pyruvate from alanine?
Aminotransferase (Transaminase)
What enzyme converts Fructose-1,6-bisphosphate to Fructose-6-Phosphate?
Fructose-1,6-bisphosphotase
What cofactor is required by the Propionyl CoA Carboxylase?
Biotin
How much energy is consumed in gluconeogenesis?
6 ATP
What cofactor is required by the MethMalonyl CoA mutase?
Vitamin B12
18 amino acids are gluconeogenic. What amino acids are strictly ketogenic and cannot be used in gluconeogenesis?
Lysine & Leucine
How can glycerol be used in gluconeogenesis?
Glycerol is produced by removing FA tails to isolate the glycerol backbone. The glycerol is phosphorylated by the glycerol kinase to produce Glucose-3-Phosphate. G3P is hydrogenated to produce DHAP which can enter into gluconeogenesis.
What enzyme converts Glucose-6-Phosphate to Glucose?
Glucose-6-Phosphotase
What are the three irreversible steps of glycolysis that must be overcome in gluconeogenesis?
Glucose –> Glucose-6-Phosphate by hexokinase
Fructose-6-Phosphate –> Frustose-1,6-bisphosphate by PFK
Phosphoenolpyruvate –> Pyruvate by PDH
How can propionate be used in gluconeogenesis?
Propionate is produced from the B-oxidation of odd-numbered FAs. Propionyl CoA carboxylase converts Propionyl CoA to MethMalonyl CoA. MethMalonyl CoA Mutase then converts MethMalonyl CoA to Succinyl CoA. Succinyl CoA is a TCA intermediate that can produce oxaloacetate. Oxaloacetate can be converted to PEP to enter gluconeogenesis.
How does the rate of gluconeogenesis change with long-term starvation?
As starvation continues, the rate of gluconeogenesis decreases. The process is energy-consuming so it is only used to produce glucose for RBCs. Producing of ketone bodies will increase.
What tissues play a major role in gluconeogenesis?
Liver; during times of extended starvation, kidney glucose production increases
What amino acids are both gluconeogenic and ketogenic?
Aromatic amino acids & isoleucine
How can glycerol be used in gluconeogenesis?
Glycerol is produced by removing FA tails to isolate the glycerol backbone. The glycerol is phosphorylated by the glycerol kinase to produce Glucose-3-Phosphate. G3P is hydrogenated to produced DHAP which can enter into gluconeogenesis.
How does glucagon stimulate gluconeogenesis?
Glucagon stimulates FA catabolism. This produces acetyl CoA and NADH. High Acetyl CoA results in the induction of the PEP Carboxykinase by PKA and the inactivation of the pyruvate kinase by phosphorylation.
What is the function of the Glucose-Lactate Cycle (Cori Cycle)?
Lactate, produced from glycolysis in RBCs, is transported to the liver. In the liver, lactate is converted to pyruvate by the lactate dehydrogenase to enter into gluconeogenesis.
How does the direct and indirect synthesis of phosphoenolpyruvate from oxaloacetate differ?
Direct - Oxaloacetate –> PEP by the mitochondrial PEP carboxykinase, using 2 GTP
Indirect - Oxaloacetate –> Malate by the mitochondrial malate dehydrogenase. Malate is relocated to the cytosol via the malate shuttle and reconverted to oxaloacetate by the cytosolic malate dehydrogenase. Oxaloacetate –> PEP by the cytosolic PEP carboxykinase using 2 GTP
