Lecture 21, Gluconeogenesis (Zaidi)

Question 1

Why is maintaining the level of glucose important?

Answer 1

Brain depends on glucose as its primary fuel and RBC use glucose as their only fuel

Question 2

How much glucose does the body need per day?

Answer 2

160 g

Question 3

How much glucose does the brain require?

Answer 3

120 g

Question 4

How much glucose is present in body fluids?

Answer 4

20 g

Question 5

How much glucose is readily available from glycogen?

Answer 5

190 g

Question 6

T or F: Direct glucose reserves are sufficient enough to meet the body’s glucose needs for about a day.

Answer 6

True.

Question 7

When is gluconeogenesis especially important?

Answer 7

During a longer period of fasting or starvation

Question 8

Where does gluconeogenesis occur?

Answer 8

In liver and kidney

Question 9

T or F: Gluconeogenesis is simply a reversal of glycolysis.

Answer 9

False. The pathway is not a reversal of glycolysis.

Question 10

What does gluconeogenesis convert?

Answer 10

Pyruvate into glucose

Question 11

What are the major precursors in gluconeogenesis?

Answer 11

Lactate, amino acids, and glycerol

Question 12

How does gluconeogenesis bypass the irreversible steps of glycolysis?

Answer 12

4 enzymes that aren’t present in glycolysis

Question 13

List the 4 enzymes that are present in gluconeogenesis but not glycolysis.

Answer 13

Pyruvate carboxylase, phosphoenolpyruate carboxykinase, fructose 1,6-bisphosphatase, glucose 6-phosphate

Question 14

What is the first step of gluconeogenesis?

Answer 14

Pyruvate is converted to oxaloacetate by pyruvate carboxylase

Question 15

Pyruvate kinase (PC) is a ___ enzyme.

Answer 15

Mitochondrial

Question 16

How is OAA transported to the cytoplasm?

Answer 16

Via malate shuttle

Question 17

What does pyruvate carboxylase use to produce OAA?

Answer 17

ATP, HCO3-

Question 18

What is the second step of gluconeogenesis?

Answer 18

Oxaloacetate is converted to PEP by phosphoenolpyruvate carboxykinase

Question 19

What does phosphoenolpyruvate carboxykinase use to produce phosphoenolpyruvate?

Answer 19

GTP

Question 20

What is the third reaction of gluconeogenesis?

Answer 20

Phosphoenolpyruvate is converted to 2-phosphoglycerate by enolase

Question 21

T or F: Enolase uses a water to produce 2-phosphoglycerate.

Answer 21

True.

Question 22

What enzyme converts 2-phosphoglycerate to 3-phosphoglyerate (4th reaction of gluconeogenesis)?

Answer 22

Phosphoglycerate mutase

Question 23

What is the 5th reaction of gluconeogenesis?

Answer 23

3-phosphoglycerate is converted to 1,3-bisphosphoglycerate by phosphoglycerate kinase

Question 24

What does phosphoglycerate kinase use to produce 1,3-bisphosphoglycerate?

Answer 24

ATP

Question 25

What is the 6th reaction of gluconeogenesis?

Answer 25

1,3-bisphosphoglycerate is converted to G3P by G3P dehydrogenase

Question 26

What does G3P dehydrogenase use to produce G3P?

Answer 26

NADH

Question 27

T or F: G3P isomerase converts G3P into DHAP.

Answer 27

False. TPI converts DHAP to G3P and vice versa.

Question 28

Which enzyme converts G3P to fructose 1,6-bisphosphate in the 8th reaction of gluconeogenesis?

Answer 28

Aldolase

Question 29

What is the 9th reaction of gluconeogenesis?

Answer 29

Fructose 1,6-bisphosphatase breaks down fructose 1,6-bisphosphate to fructose 6-phosphate

Question 30

What is the 10th reaction of gluconeogenesis?

Answer 30

F6P is isomerized to G6P by phosphoglucose isomerase

Question 31

How does G6P form free glucose?

Answer 31

By the action of glucose 6-phosphatase

Question 32

Which enzymes of the second half of gluconeogenesis use water?

Answer 32

Fructose 1,6-bisphosphatase, glucose 6-phosphatase

Question 33

Where is glucose 6-phosphatase located?

Answer 33

In lumen of ER

Question 34

Describe T1.

Answer 34

Transports glucose 6-phosphate back to ER

Question 35

Describe T2.

Answer 35

Transports inorganic phosphate back into cytosol

Question 36

Describe T3.

Answer 36

Transports glucose back to cytoplasm

Question 37

How do gluconeogenesis and glycolysis utilize ATP?

Answer 37

Glycolysis generates ATP, gluconeogenesis consumes ATP

Question 38

What determines whether glycolysis or gluconeogenesis will be activated?

Answer 38

Energy charge (ATP/ADP ratio)

Question 39

Gluconeogenesis and glycolysis are ___ regulated.

Answer 39

Reciprocally

Question 40

List the favoring conditions of glycolysis and gluconeogenesis.

Answer 40

``` Glycolysis = blood insulin concentration is high Gluconeogenesis = blood glucose concentration is low and glycogen stores are depleted ```

Question 41

What are the positive regulators of glycolysis and gluconeogenesis?

Answer 41

``` Glycolysis = glucose, insulin, AMP, fructose 2,6-BP, fructose 1,6-BP Gluconeogenesis = glucagon, citrate, cortisol, thyroxine, acetyl CoA ```

Question 42

What are the negative regulators of glycolysis and gluconeogenesis?

Answer 42

``` Glycolysis = glucagon, ATP, citrate, glucose 6-P, fructose 6-P, alanine Gluconeogenesis = ADP, AMP, fructose 2,6-BP ```

Question 43

What does fructose 2,6-BP strongly stimulate and inhibit?

Answer 43

Stimulates phosphofructokinase, inhibits fructose 1,6-BP

Question 44

Which 2 enzymes regulate the concentration of fructose 2,6-BP?

Answer 44

Phosphofructokinase 2 and fructose bisphosphatase 2

Question 45

Describe the Cori cycle.

Answer 45

Lactate produced in skeletal muscle and RBC can be converted back to pyruvate in liver; Pyruvate can enter the gluconeogenic pathway and regenerate glucose

Question 46

Except PC, where are the enzymes of gluconeogenesis found?

Answer 46

Cytoplasm