Gluconeogenesis

Question 1

What are some sources of glucose?

Answer 1

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

Question 2

Provide examples of substances pyruvate can be converted to?

Answer 2

• Alanine
• Acetyl CoA
• Lactate
• Gluconeogenesis

Question 3

What is the Cori cycle?

Answer 3

When Lactate is converted to glucose in the liver

Question 4

What enzyme turns pyruvate to gluconeogenesis?

Answer 4

Pyruvate carboxylase

Question 5

Does Gluconeogenesis consume or generate ATP?

Answer 5

Consume

Question 6

What substance does Pyruvate carboxylase require to become active?

Answer 6

Acetyl-CoA

Question 7

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

Answer 7

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

Question 8

What enzyme converts Pyruvate to oxaloacetate?

Answer 8

Pyruvate carboxylase

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

Question 9

What enzyme converts Oxaloacetate to Phosphoenolpyruvate?

Answer 9

PEP carboxykinase

- + GTP

Question 10

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

Answer 10

Mitochondria

majority occurs in cytosol

Question 11

How is oxaloacetate transfered to the cytosol?

Answer 11

Malate shuttle

Question 12

What enzymes is biotin a cofactor for?

Answer 12

Carboxylation enzymes

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

Question 13

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

Answer 13

Raw egg whites (avidin)

Question 14

What are symptoms of biotin deficiency?

Answer 14

• Dermatitis
• Glossitis
• Loss of appetite
• Nausea

Question 15

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

Answer 15

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

Question 16

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

Answer 16

Fructose 1,6 bisphosphatase 1 (rate limiting step)

PFK1 does reverse reaction

Question 17

What enzyme will high levels of ATP stimulate?

Answer 17

Fructose 1,6 bisphosphatase 1

- Rate-limiting step of gluconeogenesis

Question 18

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

Answer 18

• High = Glycolysis (PFK1)

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

Question 19

What enzyme catalyses the conversion of F6P to F26BP?

Answer 19

PFK2

Question 20

What enzyme catalyses the reaction of F26BP to F6P?

Answer 20

Fructose-1,6-bisphosphatase 2

Question 21

What substances favour glycolysis (PFK1 activity)?

Answer 21

• AMP

- Fructose 2,6 Bisphosphate

Question 22

What substances decreases glycolysis (PFK1 activity)?

Answer 22

• ATP

- Citrate

Question 23

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

Answer 23

• AMP

- F 2,6 Bisphosphate

Question 24

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

Answer 24

ATP

Question 25

Where does conversion of G6P to Glucose occur?

Answer 25

Mainly in liver and kidneys | - Other organs shunt G6P -> Glycogen

Question 26

What enzyme converts G6P to Glucose?

Answer 26

Glucose-6 Phosphatase

Question 27

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

Answer 27

In certain tissues G6P can be shunted to glycogen

Question 28

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

Answer 28

Endoplasmic reticulum

Question 29

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

Answer 29

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

Question 30

What kind of fatty acids can be converted to glucose?

Answer 30

Odd chain fatty acids

Question 31

How are odd chain fatty acids converted to glucose?

Answer 31

Propionyl coA - > OAA - > PEP - > Glyceraldehyde-3-phosphate - > F1,6, BP - > Glucose

Question 32

How is glycerol converted to glucose?

Answer 32

Glycerol - > Dihyfroxyacetone phosphate - > F-1,6-BP - > Glucose

Question 33

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

Answer 33

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