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GI I > Gluconeogenesis > Flashcards

Gluconeogenesis Flashcards

1
Q

What will be used to supply the bodies glucose when fasting for less than 24 hours?

A

Liver glycogen

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2
Q

What supplies the body with glucose overnight?

A

Glycogenolysis and gluconeogenesis about equally

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3
Q

What are the major tissues for gluconeogenesis?

A

Liver and kidney

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4
Q

When does the kidneys contribution to gluconeogenesis become more important?

A

With starvation

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5
Q

What are the noncarbohydrate for gluconeogenesis?

A

Glycerol
Glucogenic AA
Lactate
Propionate - minor in humans

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6
Q

What are the three reactions that prevent gluconeogenesis from being a reversal of glycolysis?

A

Hexokinase
PFK-1
Pyruvate kinase

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7
Q

How does gluconeogenesis bypass pyruvate kinase?

A

Changes pyruvate into oxaloacetate by pyruvate carboxylase
Changes oxaloacetate to phosphoenolpyruvate by PEP carboxylase

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8
Q

What is required to change pyruvate to oxaloacetate?

A

ATP to ADP with Mg
Biotin
Mn
CO2
H2O

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9
Q

Where does the reaction of pyruvate to oxaloacetate take place?

A

Mitochondria

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10
Q

How is oxaloacetate transported from the mitochondria to the cytosol?

A

It is reduced to malate and reoxidized in the cytosol using NAD

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11
Q

What is required to change oxaloacetate into phosphoenolpyruvate?

A

GTP to GDP
Produces CO2

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12
Q

How does gluconeogenesis bypass PFK-1?

A

Fructose-1,6P to fructose 6P by fructose-1,6-bisphosphatase
Using H2O and resulting in a Pi

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13
Q

How does gluconeogenesis bypass hexokinase?

A

Glucose-6P to glucose by glucose-6-phosphatase with H2O

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14
Q

Where does the reaction catalyzed by glucose 6 phosphate take place?

A

Membrane of ER

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15
Q

How many pyruvates are needed to make 1 glucose?

A

Two

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16
Q

What is the energy investment needed for gluconeogenesis?

A

4 ATP
2 GTP

17
Q

How does glucagon affect gluconeogenesis through induction/repression?

A

Stimulates production of phosphoenolpyruvate carboxykinase and F1,6-bisphosphotase, thereby increasing gluconeogenesis
It also represses the transcription of enzymes used in glycolysis

18
Q

How do glucagon and epinephrine increase gluconeogenesis through phosphorylation?

A

Bind to g-protein, increasing concentration of cAMP. This activate cAMP dependent protein kinase which will phosphorylate PK and inactivate it.

19
Q

How does acetyl CoA affect gluconeogenesis?

A

It is an activator of pyruvate carboxylase and inhibits PDH

20
Q

What is an inhibitor of pyruvate carboxylase?

A

ADP

21
Q

What activates F1,6-bisphosphatase?

A

Citrate

22
Q

What inhibits F1,6-bisphosphatase?

A

AMP
F2,6 bisphosphate

23
Q

What AAs are not glucogenic?

A

Leucine
Lysine

24
Q

What is the Cori cycle?

A

Lactate produced in muscle is transported to liver and turned back into glucose. The glucose is released from the liver and returned to the muscles.

25
Q

Where does glycerol enter the pathway for either gluconeogenesis or glycolysis?

A

DHAP - dihydroxyacetone phosphate

26
Q

How is DHAP made from glycerol?

A

In liver and kidneys. Glycerol to glycerol phosphate by glycerol kinase using ATP.
Glycerol phosphate to DHAP by glycerol phosphate DH using NAD

27
Q

What is required as a coenzyme to change propionate to succinyl CoA?

A

Vitamin B12

28
Q

How can raw egg whites affect gluconeogenesis?

A

They contain avidin which binds biotin preventing its absorption in the intestine. Biotin is needed for pyruvate carboxylase activity.

29
Q

How can alcohol inhibit gluconeogenesis?

A

Results in excessive NADH inhibiting FA oxidation.
Favors pyruvate to lactate to make NAD, instead of gluconeogenesis pathway.

30
Q

Why can there be hypoglycemia in premature and LBW infants?

A

Little adipose tissue for FA oxidation
Immature gluconeogenesis enzymes
Inadequate stores of glycogen

31
Q

Why may there be hypoglycemia in an infant with a diabetic mother?

A

Hyperglycemia from mother leads to hyperplasia of pancreatic islet cells that produce more insulin - baby fails to suppress excessive insulin production after birth

GI I (19 decks)

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