Metabolism 04- Gluconeogenesis Flashcards
Two pathways that form free glucose
Glycogenolysis and gluconeogenesis
Tissues that supply the major gluconeogenic precursors
Muscle (alanine), red blood cells
RBCs: Lactate
Muscle: Alanine
Why do even number fatty acids not lead to an increase in net synthesis of glucose
Because you need to generate 3 carbon molecules to get proprionyl coA –> oxaloacetate –> pyruvate
Consequences of glycolysis and gluconeogenesis occurring simultaneously in same cell
no net energy gain for tissues that need it
What tissues will likely utilize much of the glucose formed by gluconeogenesis during a prolonged fast / exercise?
Brain during prolonged fast, as well as RBCs. The skeletal muscle will also use a lot during exercise
Substrate whose oxidation provides much ATP needed for gluconeogenesis
Fatty acids
Relationship between gluconeogenesis from amino acids and ureagenesis
Breakdown of amino acids like alanine generates ammonia, which is toxic and needs to be disposed of. To get rid of it, the liver puts it through the urea cycle so it can be safely disposed of – this in itself is energy costly meaning glucose from alanine requires 10ATP, not 6.
4 enzymes that catalyze the three irreversible steps of gluconeogenesis
Pyruvate carboxylase
PEP carboxykinase
Fructose 1,6 Bisphosphatase
Glucose - 6 - phosphatase
Allosteric regulation of glycolysis and gluconeogenesis comparison: Glucokinase/hexokinase vs glucose 6 phosphatase
glucokinase/hexokinase is activated by glucose and insulin
Glucose 6 phosphatase is inactivated by glucose and insulin, activated by glucagon
Allosteric regulation of glycoloysis and gluconeogenesis: PFK1 and Fructose 1,6 bisphosphatase
PFK1 : inhibited by ATP and citrate, activated by AMP and F26BP
Fructose 1,6 bisphosphatase: Inactivated by AMP and F26BP
Allosteric regulation of glycolysis and gluconeogenesis: Pyruvate kinase vs PEP carboxykinase and Pyruvate carboxylase
Pyruvate kinase: Inhibited by glucagon and ATP
PEP carboxykinse (PEPCK): glucagon promotes, insulin inhibits
Pyruvate carboxylase: Acetyl Co-A promotes
Specific response element that likely mediates effects of glucagon on gene transcription
CREB
How does ethanol metabolism reduce the concentration of 2 intermediates in gluconeogenesis
Ethanol metabolism changes NADH/NAD+ ratio
Moreover ethanol uses pyruvate and oxaloacetate in its degradation
Two tissues with highest concentration of glycogen
Muscle, liver
