Gluconeogenesis

Question 1

What is the starting molecule of gluconegenesis?

Answer 1

Pyruvate

Question 2

Why are the three main regulatory steps expensive to bypass?

Answer 2

Because the delta G is not very favorable whereas the rest of glycolysis has a delta G close to 0

Question 3

How is PK bypassed in gluconeogenesis?

Answer 3

It is a 2 step process involving Pyruvate Carboxylase and PEP carboxykinase. It is a bit complicated becasue Pyruvate is converted to oxaloacetate (via pyruvate carboxylase), then to malate, then its transportedoutside of the mitochondria, then its converted back to oxaloacetate THEN PEP Carboxykinase converts it to PEP

Question 4

What are the 3 high energy irreversible steps of glycolysis that gluconeogenesis must bypass?

Answer 4

PEP, PFK1, and Hexokinase

Question 5

How does gluconeogenesis bypass PFK1?

Answer 5

Fructose 1,6-Bisphosphatase, G6Phosphatase

Question 6

Where does gluconeogenesis occur?

Answer 6

Liver and kidneys

Question 7

The first reaction of gluconeogenesis takes place in the mitochondria, whereas the second reaction occurs in the cytoplasm. These reactions are segregated inside different cellular compartments in order to…

Answer 7

It prevents the conversion of pyruvate to PEP as pyruvate emerges from glycolysis. Because the first step of gluconeogenesis occurs in mitochondria and glycolysis takes place in the cytoplasm, the two cycles are spatially separated and can be regulated more easily. Pyruvate coming out of glycolysis will not be converted into PEP, because the enzyme that converts pyruvate to oxaloacetate is located inside mitochondria.

Question 8

True or False: Lactate can be shunted into gluconeogenesis

Answer 8

True.

Lactate can be converted into pyruvate and fed into gluconeogenesis. Lactate comes from lactic acid fermentation.

Question 9

True or False: glycerol can be shunted into gluconeogenesis

Answer 9

Glycerol, which is derived from the breakdown of triglycerides, can be converted into pyruvate. Pyruvate can enter gluconeogenesis.

Question 10

What are the glucogenic amino acids?

Answer 10

All amino acids except leucine and lysine can be converted into pyruvate in preparation for gluconeogenesis, which means glycine is a gluconeogenic amino acid.

Question 11

Which hormone is associated with gluconeogenesis?

Answer 11

Glucagon

Question 12

How does the cell concentration of acety co-A impact gluconeogenesis?

Answer 12

High levels of acetyl coa promote gluconeogenesis

Question 13

How is F16BPhosphatase regulated?

Answer 13

It is inhibited by AMP and inhibited by F26BP

Question 14

F26BP

Answer 14

Upregs PFK1, Inhibs F16BP

Question 15

How does a high intracellular concentration of acetyl Co-A affect glucose metabolism?

Answer 15

It promotes the conversion of pyruvate to oxaloacetate

Question 16

How does glucagon affect gluconeogenesis?

Answer 16

Glucagon reduces the amount of fructose 2,6-bisphosphate in the cell, thereby promoting gluconeogenesis.

Question 17

True or false: Glycerol and lactate can be used as substrates for gluconeogenesis.

Answer 17

True

Question 18

A certain metabolic process in the liver produces NADH as a part of the process. If this process is up-regulated, which of the following effects associated with gluconeogenesis is most likely to follow?
A. Intracellular levels of oxaloacetate will increase
B. Plasma Glucose concentrations will increase significantly
C. Rate of gluconeogenesis in the liver will decrease
D. Plasma glucose concentrations will decrease significantly

Answer 18

C. Rate of gluconeogenesis in the liver will decrease

The more NADH you have the less NAD+ you have so you will decrease the production of pyruvate because it is coupled to the production of NADH from NAD+

Refer to Question 11 of P/C practice Exam 4 Blueprint

Question 19

How would increasing levels of glucagon and pyruvate/acetyl co-a impact gluconeogenesis?

Answer 19

Gluconeogenesis is upregulated by glucagon and by the presence of surplus pyruvate/acetyl-CoA.

Question 20

True or False: Gluconeogenesis and glycolysis need to be separated

Answer 20

True, glycolysis and gluconeogenesis need to be separated in order to prevent a futile cycle in which glucose is broken down to pyruvate and then pyruvate is built back up into glucose.

Question 21

The conversion between glucose and pyruvate strongly favors the formation of pyruvate, and yet the gluconeogenic pathway is able to utilize several shared enzymes with glycolysis to create glucose from pyruvate. It is able to do this because…?

Answer 21

the formation of glucose, fructose-6-phosphate, and PEP through gluconeogenesis-specific enzymes push the equilibrium of reactions catalyzed using shared enzymes to favor gluconeogenesis.

Question 22

Why must oxaloacetate be converted to malate in gluconeogenesis?

Answer 22

Malate can be transported out of the mitochondria

Question 23

Where does the first and second step of Pyruvate–> PEP take place?

Answer 23

The first step is in the mitochondria. Pyrivate gets converted to oxaloacetate then to malate. Malate is transported out of the mitochondria and then back to oxaloacetate and then to PEP.

Question 24

What metabolic precursors can be fed into gluconeogenesis?

Answer 24

Pyruvate from Glucogenic amino acids, Glycerol form TAGs, Lacatate from fermentation.

Question 25

True or False: Acetyl coA can be fed into gluconeogenesis

Answer 25

No it cannot.

Question 26

What does the PFK2 have to do with gluconeogenesis?

Answer 26

So its a bit complicated but hormonal control of gluconeogenesis/glycolysis is contingent on the dual action of PFK2/F2,6Bisphosphatase.
Insulin upregulates PFK2
Glucagon downregulates PFK2 and upregs F2,6Bisphosphatase.
Deactivating PFK2 decreases the level of F26BP which will casue glycolysis to hault. The concentration of F26BP plays a huge role in the control of these two pathways.

Question 27

True or False: Most steps in glycolysis have a deltaG close to 0

Answer 27

True