Chapter 17: Gluconeogenesis Flashcards Preview

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Flashcards in Chapter 17: Gluconeogenesis Deck (68):
1

Where are the major sites of gluconeogenesis?

Liver and kidneys

2

Gluconeogenesis is important for maintaining ________ during _____.

Normal blood glucose levels during starvation

3

Brain uses only glucose, therefore the liver essentially works to...

Make the brain happy by maintaing blood glucose levels

4

Most of the glucose generated in gluconeogenesis is used by _____ and ______.

Brain and contracting muscle

5

Gluconeogenesis converts ______ to ______.

Pyruvate to Glucose

6

What are the three precursors for gluconeogenesis?

  1. Lactate (muscle)
  2. Amino acids
  3. Glycerol (adipose tissue)

Not present in glycolysis

7

Glycerol enters gluconeogenesis as...

Dihydroxyacetone phosphate

8

The 3 irreversible reactions of glycolysis are...

Bypassed in gluconeogenesis by new steps/enzymes

7/10 Enzymes are the same

9

Pyruvate kinase reaction (irreversible) of glycolysis is bypassed by:

  • Pyruvate carboxylase
  • Phosphoenolpyruvate carboxykinase (PEP)

10

Step 1 of gluconeogenesis

Pyruvate carboxylated to oxaloacetate by pyruvate carboxylase (mitochondrial enzyme)

11

First step of gluconeogenesis occurs in the...

Mitochondrial matrix

12

Oxaloacetate is transported to the cytosol as...

Malate

13

Once reoxidized in the cytoplasm, oxaloacetate is decarboxylated and phosphorylated to...

PEP by PEP carboxykinase

14

In glycolysis, PFK controls the rate. What enzyme controls the rate of gluconeogenesis, bypassing the PFK reaction?

Fructose 1,6-bisphosphatase (FBPase)

*Allosteric enzyme that controls gluconeogenesis

15

Which enzyme is critical for free glucose levels?

Glucose 6-phosphatase

*Reverse of hexokinase

16

Free glucose is generated mainly in the...

Liver

17

Glucose 6-phosphatase is present only in...

Liver and kidney

18

Glucose 6-phosphate is hydrolyzed to ______ in the _______.

Glucose in the ER lumen

19

When glucose is abundant, which process will predominate?

Glycolysis

20

When glucose is scarce, which process will take over?

Gluconeogenesis

21

Both glycolysis and gluconeogenesis are highly _____ under cellular conditions.

Exergonic

22

When synthesizing glucose from pyruvate, __________ are spent.

6 high transfer-potential phosphoryl transfer groups (4 ATP and 2 GTP)

23

What is lactic acidosis?

Accumulation of lactic acid in the blood (lowers the pH) which is caused by a deficiency in gluconeogenic enzymes

24

What is hypoglycemia?

Low blood glucose levels

-Liver cannot produce glucose to maintain normal glucose levels

25

Gluconeogenesis and glycolysis are...

Coordinated

26

Rate of glycolysis is determined by...

Glucose concentration

27

Rate of gluconeogenesis is dependent on...

Lactate concentration and other precursors

28

When high levels of AMP...

Low energy

Glycolysis turned on

Gluconeogenesis turned off

(AMP stimulates PFK, but inhibits Fructose 1,6-bisphosphatase)

29

When high levels of ATP...

High energy

Turn off glycolysis

(Citrate inhibits PFK)

30

Citrate is an activator of ________ and promotes ________.

Fructose 1,6-bisphosphatase and promotes gluconeogenesis

31

Pyruvate carboxylase - what activates/inhibits?

Activated by ADP

Inhibited by acetyl CoA

32

PEP carboxykinase is inhibited by...

ADP

33

If ATP is required, ________ predominates.

Glycolysis

34

If glucose is required, ________ is favored.

Gluconeogenesis

35

Blood glucose levels regulate glycolysis and gluconeogenesis in _____ by changing _______.

Liver

Fructose 2,6-bisphosphate levels

36

Fructose 2,6-bisphosphatase is an ________ and stimulates _______. Also inhibits __________.

Allosteric regulator

Stimulates PFK

Inhibits Fructose1,6-bisphosphatase

37

At high blood glucose levels, fructose 2,6-bisphosphate levels _____.

Increase

38

When blood glucose levels are low, fructose 2,6-bisphosphate is converted to...

Fructose 6-phosphate

39

PFK2 and FBPase2 are present in a single polypeptide chain. This is a ________ enzyme with three domains. What are they?

Bifunctional enzyme

Domains: N-terminal regulatory, kinase and phosphatase

40

PFK2 and FBPase2 are controlled ________ by ________ of a single serine residue.

Reciprocally by phosphorylation

41

Phosphorylation activates _____ and inhibits _____ to turn off _______.

FBPase 2 activated

PFK2 inhibited

Turns off glycolysis

42

When glucose is scarce, _______ levels rise in the blood and trigger a cascade of _______ to activate ____.

Which process is active? (Glycolysis/Gluconeogenesis)

Glucagon levels rise, trigger cyclic AMP and activate PKA

Gluconeogenesis is active

43

When glucose is abudant, the enzyme becomes dephosphorylated, which activates _______ and inhibits ________.

Which process is active? (Glycolysis/Gluconeogenesis)

Activates PFK2

Inhibits FBPase2

Glycolysis is active

44

Insulin levels rise after each meal in response to __________. Insulin promotes _______.

Increasing blood glucose levels

Promotes glycolysis

45

Glucagon levels rise during ______ when glucose is _____. This promotes...

Fasting when glucose is scarce

This promotes gluconeogenesis

46

Insulin normally inhibits _______. In type 2 diabetes, insulin _________. This condition is called __________.

Inhibits gluconeogenesis

Insulin fails to do this in type 2 diabetes. This is called insulin resistance. 

(Liver does not react to insulin, it just keeps making glucose, even if starving)

47

What two factors enhance insulin sensitivity?

Exercise and diet

48

What is the Cori cycle?

Lactate produced by muscle during contraction is released into the blood.

*Interrelationship between liver and muscle

Liver removes the lactate, converts to glucose via gluconeogenesis which is released into the blood and taken up by muscle.

49

What are the 3 major factors that control glycolysis and gluconeogenesis?

  1. ATP levels
  2. Citrate
  3. Blood glucose levels

50

Glycolysis:

  • Major control point
  • Fructose 2,6-bisphosphate
  • AMP
  • Citrate
  • Hormonal activation by

 
  • PFK
  • Activates
  • Activates
  • Inhibits
  • Insulin

51

Gluconeogenesis:

  • Major control point
  • Fructose 2,6-bisphosphate
  • AMP
  • Citrate
  • Hormonal activation by

 

  • FBPase
  • Inhibits
  • Inhibits
  • Activates
  • Glucagon

52

The hexokinase reaction of glycolysis is bypassed during gluconeogenesis by the enzyme:

Glucose 6-phosphatase

53

Which of the following molecules is NOT a precursor for gluconeogenesis?

Acetyl CoA

54

Which enzyme controls the rate of gluconeogenesis?

Fructose 1,6-bisphosphatase

55

Deficiencies in enzymes specific for gluconeogenesis lead to: 

Lactic acidosis and hypoglycemia

56

When blood glucose levels are high, insulin activates _______ and stimulates _______.

Activates protein phosphatase-1; glycogen synthesis

57

Which enzyme converts pyruvate to oxaloacetate in gluconeogenesis? 

Pyruvate carboxylase

58

Which compound is NOT a precursor for the synthesis of glucose by gluconeogenesis?  

Acetyl CoA

59

Which enzyme controls the rate of gluconeogenesis?

Fructose 1,6-biphosphatase

60

Deficiencies in enzymes specific for gluconeogenesis lead to: 

Lactic acidosis and hypoglycemia

61

What type of glycosidic bond causes the branching of glycogen?  

alpha 1,6-glycosidic bond

62

Glycogen phosphorylase cleaves glycogen and produces:

Glucose 1-phosphate

63

When blood glucose levels are high, insulin activates____________
and stimulates _______________.

Protein phosphatase-1; glycogen synthesis

64

Which enzyme is specific for the gluconeogenesis pathway?

Phosphoenolpyruvate carboxykinase 

65

The enzyme _______________ controls the rate of gluconeogenesis and is allosterically inhibited by high levels of _______________.

Fructose 1,6-bisphosphatase; fructose 2,6-bisphosphate

66

Glucagon ________________ glycogen degradation and signals the __________ state. 

stimulates; fasted

67

Which enzyme is NOT specific for gluconeogenesis?

Phosphoglycerate mutase

68

. Gluconeogenesis occurs in the  ____________ and is activated during ______________.    

Liver; starvation