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Biochemistry > Lecture 21, Gluconeogenesis (Zaidi) > Flashcards

Lecture 21, Gluconeogenesis (Zaidi) Flashcards

1
Q

Why is maintaining the level of glucose important?

A

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

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2
Q

How much glucose does the body need per day?

A

160 g

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3
Q

How much glucose does the brain require?

A

120 g

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4
Q

How much glucose is present in body fluids?

A

20 g

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5
Q

How much glucose is readily available from glycogen?

A

190 g

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6
Q

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

A

True.

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7
Q

When is gluconeogenesis especially important?

A

During a longer period of fasting or starvation

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8
Q

Where does gluconeogenesis occur?

A

In liver and kidney

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9
Q

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

A

False. The pathway is not a reversal of glycolysis.

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10
Q

What does gluconeogenesis convert?

A

Pyruvate into glucose

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11
Q

What are the major precursors in gluconeogenesis?

A

Lactate, amino acids, and glycerol

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12
Q

How does gluconeogenesis bypass the irreversible steps of glycolysis?

A

4 enzymes that aren’t present in glycolysis

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13
Q

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

A

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

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14
Q

What is the first step of gluconeogenesis?

A

Pyruvate is converted to oxaloacetate by pyruvate carboxylase

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15
Q

Pyruvate kinase (PC) is a ___ enzyme.

A

Mitochondrial

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16
Q

How is OAA transported to the cytoplasm?

A

Via malate shuttle

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17
Q

What does pyruvate carboxylase use to produce OAA?

A

ATP, HCO3-

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18
Q

What is the second step of gluconeogenesis?

A

Oxaloacetate is converted to PEP by phosphoenolpyruvate carboxykinase

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19
Q

What does phosphoenolpyruvate carboxykinase use to produce phosphoenolpyruvate?

A

GTP

20
Q

What is the third reaction of gluconeogenesis?

A

Phosphoenolpyruvate is converted to 2-phosphoglycerate by enolase

21
Q

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

A

True.

22
Q

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

A

Phosphoglycerate mutase

23
Q

What is the 5th reaction of gluconeogenesis?

A

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

24
Q

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

A

ATP

25
Q

What is the 6th reaction of gluconeogenesis?

A

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

26
Q

What does G3P dehydrogenase use to produce G3P?

A

NADH

27
Q

T or F: G3P isomerase converts G3P into DHAP.

A

False. TPI converts DHAP to G3P and vice versa.

28
Q

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

A

Aldolase

29
Q

What is the 9th reaction of gluconeogenesis?

A

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

30
Q

What is the 10th reaction of gluconeogenesis?

A

F6P is isomerized to G6P by phosphoglucose isomerase

31
Q

How does G6P form free glucose?

A

By the action of glucose 6-phosphatase

32
Q

Which enzymes of the second half of gluconeogenesis use water?

A

Fructose 1,6-bisphosphatase, glucose 6-phosphatase

33
Q

Where is glucose 6-phosphatase located?

A

In lumen of ER

34
Q

Describe T1.

A

Transports glucose 6-phosphate back to ER

35
Q

Describe T2.

A

Transports inorganic phosphate back into cytosol

36
Q

Describe T3.

A

Transports glucose back to cytoplasm

37
Q

How do gluconeogenesis and glycolysis utilize ATP?

A

Glycolysis generates ATP, gluconeogenesis consumes ATP

38
Q

What determines whether glycolysis or gluconeogenesis will be activated?

A

Energy charge (ATP/ADP ratio)

39
Q

Gluconeogenesis and glycolysis are ___ regulated.

A

Reciprocally

40
Q

List the favoring conditions of glycolysis and gluconeogenesis.

A 
Glycolysis = blood insulin concentration is high
Gluconeogenesis = blood glucose concentration is low and glycogen stores are depleted
41
Q

What are the positive regulators of glycolysis and gluconeogenesis?

A 
Glycolysis = glucose, insulin, AMP, fructose 2,6-BP, fructose 1,6-BP
Gluconeogenesis =  glucagon, citrate, cortisol, thyroxine, acetyl CoA
42
Q

What are the negative regulators of glycolysis and gluconeogenesis?

A 
Glycolysis = glucagon, ATP, citrate, glucose 6-P, fructose 6-P, alanine
Gluconeogenesis = ADP, AMP, fructose 2,6-BP
43
Q

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

A

Stimulates phosphofructokinase, inhibits fructose 1,6-BP

44
Q

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

A

Phosphofructokinase 2 and fructose bisphosphatase 2

45
Q

Describe the Cori cycle.

A

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

46
Q

Except PC, where are the enzymes of gluconeogenesis found?

A

Cytoplasm

Biochemistry (10 decks)

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