Exam 3/4 - Gluconeogenesis

Question 1

Pyruvate –> Phosphoenolpyruvate

• [] step reaction
• Conversion of OAA to PEP can occur in the [] or in the cytosol

Answer 1

1. 2 step
2. mitochondria

Question 2

What are the 2 steps in Pyruvate –> Phosphoenol pyruvate?

Answer 2

1. Pyruvate –> Oxaloacetate
   
   1. done by pyruvate carboxylase
   2. Uses ATP and Carbonic Acid
2. Oxaloacetate –> PEP
   
   1. done by PEPCK (phosphoenol pyruvate carboxy kinase
   2. Use GTP and produces CO2 and GDP as by-products

Question 3

In the reaction of Pyruvate –> OAA, carbonic acid is needed. What enzyme makes the carbonic acid?

What substrates are needed?

Answer 3

Carbonic anhydrase

CO2 and H2O

Question 4

What enzyme catalyzes the gluconeogenesis reaction of Fructose-1,6-bisphosphate –> Fructose 6-phosphate?

What “type” of reaction of this and what by-product is produced?

Answer 4

Fructose bisphosphatase

Hydrolysis, and removal of inorganic phosphate

Question 5

1. What enzyme catalyzes the gluconeogenesis reaction of Glucose 6-phosphate –> Glucose?
2. What “type” of reaction of this and what by-product is produced?

Answer 5

1. Glucose 6-phosphatase
2. Hydrolysis
   
   1. removal of inorganic phosphate

Question 6

Where is Glucose 6-phosphatase found in the cell?

Answer 6

• It is bound to the inside of the ER, the lumen.
• So Glu 6-P has to be transported into the ER before it can by hydrolyzed into Glucose

Question 7

How many ATP are spent to make glucose from lactate?

Answer 7

6 total

Question 8

How many ATP are spent to make glucose from “alanine?”

Answer 8

10 ATP

Question 9

When lactate dehydrogenase is reversed to produce pyruvate - [] is formed for use in Gluconeogenesis

Answer 9

NADH

Question 10

All amino acids except [] and [] can supply carbon chains to gluconeogenesis…what is their “classification?”

Answer 10

• Leucine and Lysine
• Ketogenic

Question 11

What amino acids are both Ketogenic and Glucogenic?

Answer 11

• Threonine
• Isoleucine
• Phenylalanine
• Tyrosine
• Tryptophan

Question 12

In the mitochondria - glutamate is deaminated to make alpha-ketoglutarate by what enzyme?

What is the by-product of this reaction?

Answer 12

Glutamate Dehydrogenase

Ammonia, NH4

Question 13

Pyruvate is converted to OAA by what enzyme?

Is there any ATP expenditure?

Answer 13

Pyruvate Carboxylase

1 ATP is consumed for each reaction - but to make a full glucose moleucle you’d have to do the reaction twice

SO, 2 ATP total will be used up

Question 14

Once alanine has entered the mitochondria as Pyruvate, it will then be converted to OAA…what are the 2 options for the next step for OAA?

Answer 14

1. It can be converted to Malate
2. It can be converted to Aspartate

Question 15

In mitochondria -

1. Ornithine + Carbamoyl Phosphate ==> ??
2. What enzyme does this?
3. How many ADP are consumed?

Answer 15

1. Adds Nitrogen onto citrulline
2. Ornithine Transcarbamoylase
3. No ADP are consumed!! - 2 ATP are consumed.

Question 16

In the Alanine Metabolism -

How is Malate reformed outside of the mitochondria?

Answer 16

• Fumarate is formed through Citrullines usage
• We know fumarate –> Malate from the TCA cycle

Question 17

In alanine metabolism -

1. Argininosuccinate –> [] + Arginine?
2. What enzyme catalyzes this?

Answer 17

1. Fumarate
2. Argininosuccinase

Question 18

In alanine metabolism -

1. Citrulline + Aspartate –>?
2. What enzyme catalyzes this?
3. What is the ATP expenditure?

Answer 18

1. Argininosuccinate
2. Arginiosuccinate synthetase
3. 2 ATP consumed

Question 19

In alanine metabolism -

1. Arginine –> [] + Urea?
2. What enzyme catalyzes this?

Answer 19

1. Ornithine
2. Arginase

Question 20

What is the pathway to Glucose from Odd chain Fatty Acids like Propionyl CoA?

Answer 20

• Prop CoA –> D-methylmol CoA
  
  • Proprional CoA Carboxylase
• D-methylmol CoA –> L-methylmol CoA
  
  • Epimerase
• L-Methylmol CoA –> Succinyl CoA
  
  • Mutase
• We know Succinyl CoA can go to OAA and OAA to glucose via PEPCK through gluconeogenesis

Question 21

What cell allows plants to continue with the krebs cycle in the mitochondria by creating different intermediates like - malate?

Answer 21

Glyoxysome

Question 22

What 2 enzymes are crucial for glyoxylate pathway and not found in humans (at least to our knowledge)?

Answer 22

• Isocitrate lyase
• Malate synthase

Question 23

When creating glucose from fats - what would be the first step?

Answer 23

1. Hydrolysis of acyl groups from triacylglycerol (TAG) yielding glycerol

Question 24

What are the steps to form glucose from Glycerol?

What enzyme is used at each step?

Answer 24

1. Glycerol –> Glycerol 3-phosphate
   
   1. Glycerol Kinase (Consumes 1 ATP)
2. Glycerol 3-Phosphate —> DHAP
   
   1. Glycerol 3-phosphate dehydrogenase (consumes 1 NAD+)
3. From here it can go to 2 end products
   
   1. 1/2 glucose molecule through normal gluconeogenesis
   2. It can go to lactate

Question 25

What is the first enzyme in Fructose's pathway to becoming glucose? What does it do?

Answer 25

Fuctokinase Adds a Phophate on, consumes 1 ATP

Question 26

What are the steps for Fructose --\> Glucose? What enzyme catalyzes each step?

Answer 26

* Fructose ---\> Fructose 1-phosphate * Fuctokinase (consumes 1 ATP) * Fructose 1-phosphate ---\> Glyceraldhyde or DHAP * Aldolase B * Glyceraldehyde --\> Glyceraldehyde 3-Phosphate * Triose Kinase (consumes 1 ATP) * **DHAP** ---\> can go right to Glucose * Glyceraldehyde 3-phosphate --\> Lactate

Question 27

Hydolysis of [] generates galactose?

Answer 27

Lactose

Question 28

What enzyme catalyzes Galactose --\> Galactose 1-Phosphate?

Answer 28

Galacto Kinase

Question 29

What enzymes catalyzes the isomerization of galactose 1-phosphate --\> glucose 6-phosphate? What does this enzyme need before it can catalyze this reaction?

Answer 29

1. Phosphoglucose mutase 1. Specifically - **Glucose -1,6-bisphosphosynthase** 2. It needs phosphorylation to activate first.

Question 30

What is the ATP surplus in the Kori Cycle?

Answer 30

* Psyche! * There is an ATP deficiet in the Kori cycle * **4 ATP**

Question 31

How does the liver overcome the ATP deficeit it creates by balancing gluconeogenesis with the rest of the bodies usage of glycolysis?

Answer 31

* It uses fat for energy! * Fatty Acid oxidation - generates an acetyl CoA for every 2 carbons of a fatty acid

Question 32

What 3 steps are regulated in gluconeogenesis?

Answer 32

1. Glucose 6-Phosphate ---\> Glucose 2. Fuctose 1,6-bisphosphate ---\> Fructose 6-phosphate 3. Pyruvate ---\> Phosphoenolpyruvate

Question 33

What are the different regulators of Pyruvate ---\> Phosphoenolpyruvate?

Answer 33

* Acetly CoA * (+) effector of Pyruvate ---\> Oxaloacetate * B-Oxidate promotes gluconeogenesis

Question 34

What are the effectors on Fructose 1,6-bisphosphate ---\> Fructose 6-phosphate?

Answer 34

* (-) AMP * (-) Fructose 2,6-bisphosphate * These are opposite glycolysis effector signs

Question 35

Glucagon regulation occurs by the cAMP-responsive element binding protein (CREB) that targets [] transcription of gluconeogeneic related proteins

Answer 35

Increases

Question 36

Insulin regulation occurs by the insulin-responsive element binding protein (IREB) that [] expression of gluconeogenic proteins

Answer 36

repreresses

Question 37

What transcriptional element increase/decreases gluconeogenic protein transcription in response to insulin or glucagon?

Answer 37

* CREB (cAMP-responsive element binding protein) * Increases gluconeo in response to glucagon * IREB (insulin-responsive element binding protein) * decreases gluconeo in response to insulin