Gluconeogenesis Flashcards
The whole body needs _____ grams of glucose per day
160
The daily glucose requirement of the brain is ____ grams
120
Glucose present in body fluids is ____ grams
20
Glucose readily available from glycogen is ____ grams
190
How long can you go without ingesting glucose to where your glucose reserves can compensate?
One day
_______ is especially important for during longer periods of fasting or starvation
Gluconeogenesis
What organs does gluconeogenesis occur?
Liver and Kidneys
What is Gluconeogenesis?
Synthesis of glucose from non-carbohydrate precursors
Is gluconeogenesis a reversal of glycolysis?
No, because different enzymes catalyze the reactions and oxaloacetate is used in gluconeogenesis whereas it is not found in glycolysis
What is the overall process of gluconeogenesis? (first and last molecule)
Pyruvate into glucose
What are the 3 major precursors of gluconeogenesis?
Lactate
Amino acids
Glycerol
Gluconeogenesis _____ the irreversible steps of glycolysis
Bypasses
How does gluconeogenesis bypass the irreversible steps of glycolysis?
Through the 4 enzymes not present in glycolysis:
Pyruvate Carboxylase
Phosphoenolpyruvate Carboxykinase
Fructose 1,6-Bisphosphatase
Glucose 6-Phosphatase
Where does gluconeogenesis first occur?
In the mitochondria
How does gluconeogenesis transition from beginning in the mitochondria to the cytoplasm
Pyruvate is in the mitochondria and converts to oxaloacetate, which converts to Malate. This can leave the mitochondria via the Malate Shuttle and re-convert back to oxaloacetate in the cytoplasm
List the steps of gluconeogenesis
Pyruvate is converted into oxaloacetate by pyruvate kinase
OAA is converted into phosphoenolpyruvate by phosphoenolpyruvate carboxykinase
phosphoenolpyruvate is converted to 2-Phosphoglycerate by enolase
2-Phosphoglycerate is converted into 3-Phosphoglycerate by phosphoglycerate mutase
3-Phosphoglycerate is converted into 1,3-Bisphosphoglycerate by Phosphoglycerate kinase
1,3-Bisphosphoglycerate is converted into Glyceraldehyde 3-phosphate by G3P dehydrogenase
G3P converts to Fructose 1,6-bisphosphate by Aldolase
Fructose 1,6-bisphosphate converts to Fructose 6 phosphate by Fructose 1,6 bisphosphatase
Fructose 6 phosphate converts to Glucose 6 phosphate by phosphoglucokinase
G6P is converted into Glucose by Glucose 6 phosphatase
Where is Glucose 6 phosphate located?
in the lumen of the ER
What 3 proteins are used to shuttle glucose/G6P and what does each specifically do?
T1- transports Glucose-6-Phosphate to ER
T2-transports inorganic phosphate back
T3-transports free Glucose back to the cytoplasm
Glycolysis ____ ATP, Gluconeogenesis ____ ATP
Generates
Consumes
Gluconeogenesis and Glycolysis are ______ ______
reciprocally regulated
When is glycolysis favored?
When blood [insulin] is high
When is gluconeogenesis favored?
When blood [glucose] levels are low and glycogen stores are depleted
Where does glycolysis occur? Tissue and subcellular
RBCs, exercising muscles, brain, cytosol
Where does gluconeogenesis occur? Tissue and subcellular
Liver (mostly), kidneys, and small intestines
Subcellular: mitochondria and cytosol
What are the positive regulators of glycolysis?
Glucose Insulin AMP Fructose 2,6-Bisphosphate Fructose 1,6 Bisphosphate
What are the positive regulators of gluconeogenesis?
Glucagon Citrate Cortisol Thyroxine Acetyl CoA
What are the negative regulators of glycolysis?
Glucagon ATP Citrate G6P Fructose 6 Phosphate Alanine
What are the negative regulators of gluconeogenesis?
ADP
AMP
Fructose 2,6-bisphosphate
Describe the energy usage and yield of glycolysis
Use: 2 ATP
Yield: 4 ATP
Net Yield: 2 ATP/glucose oxidized
Describe the energy usage and yield of gluconeogenesis
Use: 4 ATP, 2 GTP
Yield: 0
Net Yield: 6 ATP Equivalents/glucose oxidized
In the ______, rates of glycolysis and gluconeogenesis are adjusted to maintain blood glucose
Liver
_______ strongly stimulates Phosphofructokinase and inhibits Fructose 1,6- bisphosphatase
Fructose 2,6-bisphosphate
What 2 enzymes regulate the conc. of Fructose 2,6- bisphosphate
Phosphofructokinase 2 (PFK2) Fructose Bisphosphatase 2 (FBPase2)
What is the Corri Cycle?
Lactate produced in skeletal muscle and RBCs can be converted back to pyruvate in the liver
The pyruvate can enter the gluconeogenesis pathway and regenerate glucose (which is the source of lactate)
What is generated by the action of pyruvate carboxylase?
Oxaloacetate
What enzyme is the gluconeogenesis partner of phosphofructokinase?
Fructose 1,6 bisphosphatase
What is the most important substrate of the Corri Cycle?
Lactate
