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Biochemistry II > Gluconeogenesis > Flashcards

Gluconeogenesis Flashcards

1
Q

What is gluconeogenesis?

A

The pathway that makes glucose

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2
Q

When does gluconeogenesis take place?

A
  • Occurs when blood glucose is low.

- The hormone glucagon is involved in this process

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3
Q

What is used to make glucose during starvation, low/no carbohydraes, and exercise?

A

Starvation: primarily amino acids
Low/no carbohydrates: primarily amino acids
Exercise: lactic acid and alanine

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4
Q

What are the main non-carbohydrate precursors for gluconeogenesis?

A

Lactic acid, alpha-keto acids, and glycerol

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5
Q

How much glucose does the brain need?

A

100 grams per day (400 kcal)

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6
Q

Gluconeogenesis only occurs in special locations. What are they?

A
  • Liver (90%)

- Kidneys (10%)

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7
Q

What are the enzymes responsible for the irreversible reactions of glycolysis?

A
  • Hexokinase (glucokinase)
  • Phosphofructokinase
  • Pyruvate kinase
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8
Q

How is gluconeogenesis made favorable?

A
  • Using alternative enzymes
  • Couple the reactions to energy liberating reactions
  • Use ATP or the equivalent
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9
Q

What is the first obstacle in that gluconeogenesis must overome to proceed?

A

Converting pyruvate into phosphoenolpyruvate

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10
Q

How is pyruvate converted to phosphoenolpyruvate in gluconeogenesis?

A
  • Pyruvate is converted to oxaloacetate with pyruvate carboxylase and the coenzyme biotin
  • Oxaloacetate is converted to phosphoenolpyruvate by PEP carboxykinase
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11
Q

What is the second obstacle in that gluconeogenesis must overcome to proceed?

A

Converting fructose 1,6-bisphosphate to fructose 6-phosphate

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12
Q

How is fructose 1,6-bisphosphate converted to fructose 6-phosphate in gluconeogenesis?

A

Fructose 1,6-bisphosphate is converted to fructose 6-phosphate by fructose 1,6- bisphosphatase

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13
Q

What is the third obstacle that gluconeogenesis must overcome to proceed?

A

Converting glucose 6-phosphate into glucose

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14
Q

How is glucose 6-phosphate converted into glucose in gluconeogenesis?

A

Glucose 6-phosphate is converted into glucose by glucose 6-phosphatase

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15
Q

This is the backbone of triglycerides. It is not a fat.

A

Glycerol

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16
Q

This is the “waste” product of glycolysis.

A

Lactic acid

17
Q

These are derived from glycogenic amino acids. They can enter into TCA forming OAA, which is the direct precursor to PEP. It is the primary source of glucose from GNG at rest and during fasting.

A

Alpha-ketoacids

18
Q

What is the Cori cycle?

A

It is the process by which muscles use glycogen during exercise for the Kreb’s cycle. It produces lactate, which is then taken up by the liver to make glucose, which is sent back into the bloodstream and then stored again in muscle glycogen.

19
Q

What alpha ketoacid is alanine associated with?

A

Pyruvate

20
Q

What alpha ketoacid is glutamate associated with?

A

Alpha-ketoglutarate

21
Q

What alpha ketoacid is aspartate associated with?

A

Oxaloacetate

22
Q

What amino acid is pyruvate associated with?

A

Alanine

23
Q

What amino acid is alpha-ketoglutarate associated with?

A

Glutamate

24
Q

What amino acid is oxaloacetate associated with?

A

Aspartate

25
Q

What happens to an alpha keto acid depends on what four things?

A
  • Energy charge
  • Hormones (glucagon/insulin)
  • Glucose concentration
  • Tissue (liver vs muscle)
26
Q

Describe what happens in the glucose-alanine cycle.

A

Starts in the muslce: Glycogen–>Glucose 6P–>Pyruvate–> Alanine–>Moves to liver–>Pyruvate and NH3+–>Glucose and Urea–> glucose is transported to muscle

27
Q

When does the glucose-alanine cycle primarily occur?

A

During exercise

28
Q

This hormone is secreted by beta cells of the pancreas, it lowers blood sugar, stimulates glycogen formation, and inhibits gluconeogenesis.

A

Insulin

29
Q

This hormone is secreted by alpha cells of the pancreas, elevates blood sugar, stimulates glycogen breakdown, and stimulates gluconeogenesis.

A

Glucagon

30
Q

How does fructose 2,6-bisphosphate influence glycolysis and gluconeogenesis?

A
  • Stimulates glycolysis (stimulates PFK in the liver)

- Inhibits gluconeogenesis (inhibits fructose 1,6-bisphosphate)

31
Q

What are some stimulators of glycolysis?

A
  • Glucose
  • Insulin
  • AMP, ADP
  • NAD+
  • Fructose 2,6-bisphosphate
32
Q

What are some inhibtors of glycolysis?

A
  • ATP
  • NADPH
  • Glucagon
  • Pyruvate
  • Lactate
  • Alanine
  • Citrate
33
Q

What are some stimulators of gluconeogenesis?

A
  • Glucagon
  • Acetyl CoA
  • Citrate
34
Q

What are some inhibitors of gluconeogenesis?

A
  • Glucose
  • Insulin
  • AMP, ADP

Biochemistry II (16 decks)

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