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USMLE Biochemistry > Gluconeogenesis > Flashcards

Gluconeogenesis Flashcards

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USMLE® Step 1 flashcards
1
Q

What are some sources of glucose?

A
  • Pyruvate
  • Lactate
  • Amino acids
  • Propionate (odd chain fats)
  • Glycerol (fats)
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2
Q

Provide examples of substances pyruvate can be converted to?

A
  • Alanine
  • Acetyl CoA
  • Lactate
  • Gluconeogenesis
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3
Q

What is the Cori cycle?

A

When Lactate is converted to glucose in the liver

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4
Q

What enzyme turns pyruvate to gluconeogenesis?

A

Pyruvate carboxylase

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5
Q

Does Gluconeogenesis consume or generate ATP?

A

Consume

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6
Q

What substance does Pyruvate carboxylase require to become active?

A

Acetyl-CoA

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7
Q

What does pyruvate need t be converted to to get Phosphoenolpyruvate?

A
  • Made into Oxaloacetate (OAA) then Phosphoenolpyruvate (PEP) as PEP -> Pyruvate is an irreversible step
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8
Q

What enzyme converts Pyruvate to oxaloacetate?

A

Pyruvate carboxylase

  • Requires biotin as a cofactor
  • ATP and CO2 also required
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9
Q

What enzyme converts Oxaloacetate to Phosphoenolpyruvate?

A

PEP carboxykinase

- + GTP

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10
Q

WHere does the first step of gluconeogenesis occur (Pyruvate -> Oxaloacetate)?

A

Mitochondria

majority occurs in cytosol

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11
Q

How is oxaloacetate transfered to the cytosol?

A

Malate shuttle

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12
Q

What enzymes is biotin a cofactor for?

A

Carboxylation enzymes

  • All add 1-carbon group via CO2
  • Pyruvate carboxylase
  • Acetyl-CoA carboxylase
  • Propionyl-CoA carboxylase
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13
Q

Consumption of what can cause a biotin deficiency (rare)?

A

Raw egg whites (avidin)

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14
Q

What are symptoms of biotin deficiency?

A
  • Dermatitis
  • Glossitis
  • Loss of appetite
  • Nausea
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15
Q

What does pyruvate carboxyase present with? What are the symptoms?

A
  • Presents in infancy w. failure to thrive
  • Elevated pyruvate -> Lactate
  • Lactic acidosis
  • High alanine also
  • V. rare
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16
Q

What enzyme converts F-1,6-BP to F-6-P?

A

Fructose 1,6 bisphosphatase 1 (rate limiting step)

PFK1 does reverse reaction

17
Q

What enzyme will high levels of ATP stimulate?

A

Fructose 1,6 bisphosphatase 1

- Rate-limiting step of gluconeogenesis

18
Q

What do high and low levels of Fructose 2,6 Bisphosphate cause?

A
  • High = Glycolysis (PFK1)

- Low = Gluconeogenesis (Fructose 1,6 Bisphosphatase 1)

19
Q

What enzyme catalyses the conversion of F6P to F26BP?

A

PFK2

20
Q

What enzyme catalyses the reaction of F26BP to F6P?

A

Fructose-1,6-bisphosphatase 2

21
Q

What substances favour glycolysis (PFK1 activity)?

A
  • AMP

- Fructose 2,6 Bisphosphate

22
Q

What substances decreases glycolysis (PFK1 activity)?

A
  • ATP

- Citrate

23
Q

What substances decrease gluconeogenesis (Fructose 1,6 Bisphosphatase activity)?

A
  • AMP

- F 2,6 Bisphosphate

24
Q

What substances increase gluconeogenesis (Fructose 1,6 Bisphosphatase activity)?

A

ATP

25
Q

Where does conversion of G6P to Glucose occur?

A

Mainly in liver and kidneys

- Other organs shunt G6P -> Glycogen

26
Q

What enzyme converts G6P to Glucose?

A

Glucose-6 Phosphatase

27
Q

What molecule can be converted straight to glycogen (bypassing glucose)?

A

In certain tissues G6P can be shunted to glycogen

28
Q

Where does the reaction of G6P to Glucose occur in the cell?

A

Endoplasmic reticulum

29
Q

Where in the gluconeogenesis/glycolysis pathway does glucagon exert its effects?

A
  • Phosphoenol pyruvate -> pyruvate (slows down this reaction, less pyruvate made)
  • Induces F16BP -> F6P (through decreasing F2,6BP),
  • Induces G6P -> Glucose (more glucose produced)
30
Q

What kind of fatty acids can be converted to glucose?

A

Odd chain fatty acids

31
Q

How are odd chain fatty acids converted to glucose?

A

Propionyl coA

  • > OAA
  • > PEP
  • > Glyceraldehyde-3-phosphate
  • > F1,6, BP
  • > Glucose
32
Q

How is glycerol converted to glucose?

A

Glycerol

  • > Dihyfroxyacetone phosphate
  • > F-1,6-BP
  • > Glucose
33
Q

WHat other hormones (outside glucagon and insulin) may affect glucose levels?

A
  • Epinephrine (raises blood glucose, gluconeogenesis and glycogen breakdown)]
  • Cortisol (increases gluconeogenesis enzymes)
  • Thyroid Hormone (increases gluconeogenesis)

USMLE Biochemistry (44 decks)

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