Gluconeogenesis Flashcards
When does gluconeogenesis occur
Blood glucose is low
I.e Starvation, no carbs, exercise
What hormone stimulates gluconeogenesis
Glucagon
During starvation what is used to make glucose
Primary amino acids
during low/no carbs what is used to make glucose
Primary amino acids
During exercise what is used to make glucose
Lactic acid and alanine
What are the main non-carbohydrate precursors for glucose
Lactic acid
a-keto acids
glycerol
What are the entry metabolites for gluconeogenesis
Pyruvate
Oxaloacetate
DHAP
How much glucose does the brain need a day
100 grams (400 kcal)
What accounts for 60-70% of our resting energy expenditure in adults
Brain
Liver
Heart
Kidneys
What is the main location for gluconeogenesis
the liver
what are the three irreversible reactions of glycolosis
Hexokinase
Phosphofructokinase
Pyruvate kinase
What is the first step in gluconeogenesis
Turn pyruvate into Phosphoenolpyruvate
how is pyruvate turned into PEP
Pyruvate–>Oxaloacetate–>PEP
Where in the liver does pyruvate get turned into PEP
The mitochondria
How does oxaloacetate exit the mitochondria
It gets converted into malate (carnatine shuffle)
What enzyme converts pyruvate into oxaloacetate
Pyruvate carboxylase
What co-enzyme is required to run pyruvate carboxylase
Biotin
What enzyme converts oxaloacetate into PEP
PEP carboxykinase
What regulates the activity of pyruvate carboxylase
Acetyl CoA produced during FA oxidation
What co-factor is required for PEP carboxykinase
Magnesium
What is different in the first step of gluconeogenesis if Lactate is the precursor.
PEP is made in the mitochondria instead of the cytosol. PEP will then be transported out of the mitochondria into the cytosol
What high energy compounds are needed to convert Pyruvate to PEP
ATP (Pyruvate–>OAA)
GTP (OAA–>PEP)
What is the reason for the malate shuttle
To produce NADH to be used as a reducing power in further reactions
What is the second obstacle of gluconeogenesis
Fructose-1,6-bisphosphate –> Fructose-6-phosphate
What enzyme converts Fructose -1,6-bisphosphate into fructose-6-phosphate
fructose-1,6-biphosphatase
What co-factor is required for Fructose-1,6-bisphosphatase
Magnesium
What is the third obstacle of gluconeogenesis
Glucose-6-phosphate –> glucose
What enzyme converts glucose-6-phosphate into glucose
glucose-6-phosphatase
What co-factor is needed for glucose-6-phosphatse
Magnesium
To form a glucose from pyruvate, how much energy is used
4 ATP
2 GTP
2 NADH
What are the gluconeogenic substrates
Glycerol
Lactic acid
a-ketoacids (from AA)
What is glycerol found in the body
The backbone of triglycerides
Is glycerol a major source for making glucose
No
What are the steps to convert glycerol into a usable substate for gluconeogenesis
Glycerol –>glycerolphosphate–>DHAP
What is the cycle that converts lactic acid into glucose
Cori cycle
Where is lactic acid converted into glucose
The liver
Where is lactic acid accumulated during exercise
Skeletal muscles
What is the carbon skeleton of amino acids
a-ketoacids
What stimulates the conversion of amino acids into glucose
starvation or low carbohydrate intake
What is the glucose-alanine cycle
Glutamate + Pyruvate = alanine (in muscles)
alanine moved to liver
Alanine + a-ketoacid = glutamate + pyruvate
Pyruvate –> glucose
Glucose to mucles
What hormone inhibits gluconeogenesis
Insulin
What hormone stimulates gluconeogenesis
glucagon
What affect does fructose-2,6-bisphosphate have on gluconeogenesis
It inhibits its (inhibits fructose-1,6-bisphosphate
Stimulates glycolosis (stimulate PFK)
What things stimulate gluconeogensis
Glucagon
Acetyl CoA
Citrate
What inhibit gluconeogenesis
Glucose
Insulin
AMP, ADP
Fructose-2,6-bisphosphate
What stimulate glycolosis
Glucose Insulin AMP, ADP NAD+ Fructose-2,6-bisphosphate
What inhibit Glycolosis
ATP NADH Glucagon Pyruvate Lactate Alanine Citrate
