Gluconeogenesis Flashcards
what level is the most potent promoter of glycolysis or gluconeogenesis
Blood glucose (bg) level
what occurs in the fed state (after eating)
Decrease in glucagon
Increase in insulin, glycolysis, glycogen synthesis, amino acid synthesis, fatty acid synthesis
what occurs in the fasted state
decrease insulin
increase glucagon, fatty acid oxidation, amino acid breakdown, gluconeogenesis, glycogenolysis
how many calories worth of energy does the body store as glycogen
2000
What is Gluconeogenesis
Synthesis of glucose from non-carbohydrate precursors (pyruvate, lactate, glycerol
what does gluconeogenesis maintain
maintenance of blood glucose levels during starvation or vigorous exercise
where does gluconegensis occur
mainly in the liver and to a lesser extent in the kidney
what makes up glucose
60% Certain AA – degradation of muscle protein
28% Lactate – from anaerobic glycolysis in exercising muscle “Cori cycle”
12% Glycerol – breakdown of triacylglycerol in adipose
what are the 3 irreversible enzymes of glycolysis
Hexokinase (1) converts glucose to glucose 6-phosphate
Phosphofructokinase (2). converts fructose 6-phosphate to fructose-1,6-bisphosphate
Pyruvate kinase (3) converts phosphoenolpyruvate to pyruvate
what can any metabolite be converted into
pyruvate or oxaloacetate
what does the conversion of lactate to glucose require
energy which is derived from the oxidation of fatty acids in the liver.
where does glucose produced by the liver enter
the bloodstream for delivery to peripheral tissues and the cori cycle
what is the Cori cycle
Metabolism under conditions of vigorous exercise (limited oxygen)
represents the transfer of chemical potential energy in the form of glucose from the liver to peripheral tissues
what enzymes aren’t cytosolic
Glucose 6-phosphatase - ER
Pyruvate carboxylase - mitochondria
PEP carboxykinase - cytosolic and mitochondrial
where is oxaloacetate produced
mitochondria
where does the conversion of Oxaloacetate to PEP(Phosphoenolpyruvate)
and PEP to Glucose
cytoplasm
what energy requirement is needed for gluconegenesis
4 ADP 2 GDP 2NAD
what happens in low energy charge
glycolysis on (to generate ATP)
Gluconeogenesis off (requires ATP)
What happens in high energy charge
glycolysis off (sufficient ATP)
gluconeogensis on (requires ATP)
What is the equation for low energy charge
ADP + AMP = PEPCK + PC + Fructose-1,6-Bpase (off) PFK-1 (on)
what is the equation for high energy charge
ATP = Pyruvate Kinase + PFK-1 (0ff)
what happens in the fed state in healthy individuals
insulin represses PEPCK and gluconeogenesis is off
what occurs in the fed state in diabetes mellitus
insulin doesn’t repress PEPCK and gluconeogenesis is on and produces glucose
what can glucose be incorporated into
storage polysaccharides
After conversion to glucose 6-phosphate, where can glucose enter
the PPP (aka hexose monophosphate shunt)
what is the PPP
it runs parallel to glycolysis
what is the formula for the pentose phosphate pathway
C5H10O5
what is the Pentose Phosphate Pathway active in
the tissues that synthesise fatty acids or steroids (mammary glands, adrenal cortex, liver)
what is consumed in the Pentose Phosphate Pathway
NADPH
What is the Pentose Phosphate Pathway an important process in
RBCs
what stages are in the Pentose Phosphate Pathway
Divided into oxidative (NADPH produced) and non-oxidative stages (production of 5 carbon sugars)
what fuel is glucose
major metabolic fuel
what is insulin and glucagon release driven by
blood glucose level
what organ relies on glucose for energy
the brain
When dietary glucose is consumed by tissues, what happens
liver glycogen and gluconeogenesis (from lactate, glycerol and alanine) become the sources of glucose
