Gluconeogenesis Flashcards
3 reactions that require different enzymes and processes from glycolysis
pyruvate to PEP
Fructose1,6 bis-phosphate to fructose 6 phosphate
Glucose 6 phosphate to glucose
Average human uses around ___ g of Glucose per day
160
three major carbon sources for Gluconeogenesis
Lactate
Amino acids
Glycerol
Lactate Dehydrogenase
converts lactate to pyruvate
producing NADH in process
Cori cycle
Shuttling of lactate from cells to only place, Liver, where it can be converted into Glucose
Two amino acids that do not participate/contribute to Gluconeogenesis
Lysine
Leucine
Amino acids are used to generate pyruvate
From fatty acids, Gluconeogenesis uses …
the triacylglycerol portion only
Glycerol is used to make …
DHAP
GNG occurs during fasting but also during ….
prolonged exercise
high protein diets
stress
Major substrates that stimulate GNG
Glycerol
Lactate
Amino acids - released from muscle when insulin levels are low, if from dietary protein then requires Low carb intake as well
Conversion of Pyruvate to PEP requires
Pyruvate dehydrogenase is inactive
Pyruvate carboxylase is active
PEPCK is induced
Induced vs. Activated enzymes
Activated - enzyme already made and it ready to be turned off/on
Induced - the enzyme needs to be made
Biochemically, Fasting leads to low insulin, adipose breaks down, elevated glucagon. The glucagon activates …
Adenylate cyclase which converts ATP to cAMP
cAMP will induce the transcription of PEPCK which converts OAA to PEP
Fatty acids travel to liver and oxidation leads to acetylCoA, NADH and ATP leading to depletion of ADP which inhibits pyruvate dehydrogenase keeping pyruvate from going to the TCA cycle
Acetyl CoA activates pyruvate carboxylase
Under non fasting conditions, Epinephrine during stress…
activates adenylate cyclase
Glucagon phosphorylates pyruvate kinase to …
inhibit the enzyme and stop the rxn from re-converting PEP back into pyruvate
High insulin during fasting leads
to an increase in F2,6 BP, while glucagon leads to a decrease in F2,6BP
F2,6BP activates
glycolytic enzyme, Phosphofructokinase
and it inhibits gluconeogenic enzyme F1,6BP
hence fasting leads to inhibition of kinase and activation of phosphatase
Glucokinase has high Km for glucose meaning …
low affinity for glucose
Insulin ____ more GK
…
A patient comes in for a glucose tolerance test. 30 minutes after ingesting a high glucose beverage, which liver enzymes would be active?
Glucokinase and PFK1
what enzymes in the gluconeogenic pathway would be inhibited when the glycolytic pathway is activated?
PEPCK Fructose 1,6 Biphosphate pyruvate kinase pyruvate carboxylase glucose 6 phosphate
Hormonally, what does Fasting do?
decrease insulin and increase glucagon
what inhibits glycolysis and promotes gluconeogenesis?
Glucagon
cAMP
acetyl CoA
What does cAMP induce transcription of?
PEPCK
Acetyl CoA
these are breakdown products of fatty acid metabolism
which will activate pyruvate carboxylase
Fructose 2,6 Bisphosphate will ____ gluconeogenesis and ______ glycolsis
inhibit
promote
Describe the hormonal levels in the fed state
high insulin levels occur so glycolysis is favored and gluconeogenesis is inhibited
induced vs. active
induced means that enzyme needs to be made
active already made and ready to be turned on or off
what is the key starting ingredient for gluconeogenesis?
pyruvate which is formed lactate and amino acids
