Exam 2 Lecture 16 Gluconeogenesis Flashcards
whole body needs about _ g glucose per day
160 g
daily glucose requirement of brain is about _ g
120 g
glucose present in body fluids is about _ g
20 g
glucose readily available from glycogen is about _ g
190 g
glycogen is the storage form of _
glucose
glycogen is stored where
liver and the muscle
what is the purpose of a glycogen reserve?
the reserve of 190 g is sufficeint to meet glucose needs for about a day (fasting)
gluconeogenesis occurs where?
liver and kidney
Major 3 precursors of gluconeogenesis:
- lactate
- amino acids
- glycerol
what is the 1st step in gluconeogenesis?
pyruvate first converted to oxaloacetate (OAA)
pyruvate is converted into OAA via
enzyme pyruvate carboxylase (PC)
why is the compartmentalization of PC into the mitochondria important?
malate shuttle transports OAA to cytoplasm
what is the 2nd step in gluconeogenesis?
OAA converted into PEP
OAA converted into PEP via?
phosphoenolpyruvate carboxykinase
what is the 3rd step in gluconeogensis?
PEP converted into 2-PG
PEP converted into 2-PG via?
enolase (same as in glycolysis)
what is the 4th step in gluconeogenesis?
2-PG converted into 3-PG
2-PG converted into 3-PG via
phosphoglycerate mutase (same as in glycolysis)
what is the 5th step in gluconeogenesis?
3-PG converted into 1,3-BPG
3-PG converted into 1,3-BPG via?
phosphoglycerate kinase (same as in glycolysis)
what is the last step in gluconeogenesis?
1,3-BPG into GAP
1,3-BPG into GAP via?
glyceraldehyde 3-phosphate dehydrogenase (same as in glycolysis) GAPDH
From GAP to glucose:
GAP + _ forms fructose 1,6-BP
DHAP
glycerol enters the pathway via
DHAP
lactate (and some amino acids) enters the pathway via
pyruvate
amino acids enters the pathway via
OAA
what is the rate limiting enzyme of gluconeogenesis?
Fructose 1,6-bisphosphatase
From GAP to glucose:
in 2nd step, Fructose 1,6-bisphosphatase breaks down _ into _
fructose 1,6-BP to F6P
From GAP to glucose:
in the 3rd step, F6P is _ to G6P via _
F6P is isomerized to G6P via phosphoglucose isomerase (same as in glycolysis)
From GAP to glucose:
in the last step, G6P forms free glucose by the action of _. Free glucose can leave liver and enter blood.
glucose 6-phosphatase
glucose 6-phosphatase is located where?
in the lumen of the ER
gluconeogeneis “by-passes” the irreversible steps of glycolysis via what 4 enzymes NOT present in glycolysis?
- pyruvate carboxylase (PC)
- phosphoenolpyruvate carboxykinase
- fuctose 1,6-bisphosphatase
- glucose 6-phosphatase
2 pyruvate enters into gluconeogenesis to form 1 molecule of _
glucose
what are the 3 points of ATP/GTP consumption in gluconeogenesis?
- converting pyruvate into OAA
- converting OAA into PEP
- converting 3-PG into 1,3-BPG
gluconeogenesis and glycolysis are _ regulated
reciprocally regulated
what are the modulators/activators in glycolysis
- F-2,6-BP and AMP stimulates phosphofructokinase in glycolysis
- F-1,6-BP stimulates pyruvate kinase in glycolysis
what are the modulators/inactivators in glycolysis
- ATP, citrate, and H+ de-stimulates phosphofructokinase in glycolysis
- ATP and alanine de-stimulates pyruvate kinase in glycolysis
what are the modulators/activators in gluconeogenesis
- Citrate stimulates fructose 1,6-bisphosphatase in gluconeogenesis
what are the modulators/inactivators in gluconeogenesis
- F-2,6-BP and AMP de-stimulates fructose 1,6-bisphosphatase in gluconeogenesis
- ADP de-stimulates PC and phosphoenolpyruvate carboxykinase
glucagon, when released, stimulates a kinase or phosphatase?
kinase
insulin, when released, stimulates a kinase of phosphatase?
phosphatase
F6P is converted into fructose 2,6-BP via _
phosphofructokinase 2 (PFK2)
PFK2 has what kind of domains?
a kinase and a phosphatase domain
Fructose 2,6-BP is a strong signalling molecule for _
phosphofrutokinase (PFK; rate limiting step of glycolysis)
the concentration of Fructose 2,6-BP is controlled what kind of enzyme?
a bi-functional enzyme with a kinase and a phosphatase domain: PFK2 and FBPase 2 (fructose bisphosphatase)
T/F: Fructose 2,6-BP stimulates or inhibits glycolysis
true
the activity of the bi-functional enzyme is regulated by what 2 hormones?
insulin and glucagon
_ stimulates a phosphatase and PFK2 is activated so glycolysis is active
insulin stimulates a phosphatase and PFK2 is activated
glucose is abundant
_ stimulates PKA and FBPase 2 is activated so glycolysis is inhibited and gluconeogenesis is stimulated
glucagon stimulates PKA and FBPase 2 is activated
when blood glucose is scarce
The Cori Cycle:
lactate is produced in skeletal muscle and RBCs and can be converted back to pyruvate in the _. This location does the reverse to make pyruvate into _ so it can be thrown back into the blood and muscle can pick it up.
liver
glucose
