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Biochemistry II Final > Pentose Phosphate Pathway > Flashcards

Pentose Phosphate Pathway Flashcards

0
Q

What is the main enzyme in PPP?

A

Glucose 6 phosphate dehydrogenase

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1
Q

What does PPP start with?

A

Glucose 6 phosphate

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2
Q

What is made in the PPP?

A

Ribose and NADPH

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3
Q

Where is the PPP located in the cell?

A

Cytosol

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4
Q

How many NADPH are made in the PPP from each glucose 6 phosphate?

A

2

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5
Q

What else is made from the irreversible reaction in PPP besides NADPH?

A

Ribose 5 phosphate

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6
Q

What is another named for the PPP?

A

Hexose monophosphate pathway

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7
Q

Is ATP produced or consumed in the PPP?

A

Neither! (Unique)

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8
Q

What are the two purines?

A

Guanine and adenine

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9
Q

What are the two pyrimidines?

A

Thymine and cytosine (for DNA) & uracil and cytosine (for RNA)

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10
Q

What is a nucleoside?

A

Nitrogenous base + sugar

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11
Q

What is a nucleotide?

A

Nitrogenous base + sugar + phosphate

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12
Q

What do we need ribose 5 phosphate for?

A

ATP, coenzyme A, NAD, FAD, nucleic acids

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13
Q

What stimulates PPP overall?

A

Anything that consumes ribose 5 phosphate

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14
Q

What do we use NADPH for?

A

Reductive biosynthesis, free radical elimination (antioxidant regeneration), detoxification, respiratory bursts

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15
Q

Is NADPH an electron donor or acceptor?

A

Donor

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16
Q

Is the first irreversible reaction of PPP oxidative or reductive?

A

Oxidative

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17
Q

What are products of the reversible, non-oxidative reactions of PPP?

A

Products that can be utilized in glycolysis if we need energy (G3P, fructose 6 phosphate, etc…)

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18
Q

Dehydrogenation of what substance occurs in the first step of PPP?

A

Glucose 6 phosphate

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19
Q

Hydrolysis of what substance occurs in the second step of PPP?

A

6 phosphate gluconate alpha lactone (6-phosphogluconolactone)

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20
Q

What occurs in the third step of oxidative decarboxylation in PPP?

A

Occurs to 6-P gluconate to yield ribulose 5 phosphate

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21
Q

What occurs in the fourth isomeric action step in PPP?

A

Ribulose 5 phosphate to ribose 5 phosphate

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22
Q

What are the reactants for the enzyme glucose 6 phosphate dehydrogenase?

A

Glucose 6 phosphate and NADP+

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23
Q

What is the product of the enzyme glucose 6 phosphate dehydrogenase?

A

NADPH

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24
Q

What enzyme is responsible for the oxidization of glucose 6 phosphate in the first step of PPP?

A

Glucose 6 phosphate dehydrogenase (main enzyme of PPP)

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25
Q

What effect does NADPH have on glucose 6 phosphate dehydrogenase?

A

Inhibition (because it’s a product)

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26
Q

What enzyme is responsible for the hydrolysis reaction that is the second step of PPP?

A

Lactonase

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27
Q

What compound is used during the hydrolysis reaction in PPP using lactonase?

A

H20 (water)

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28
Q

What enzyme is responsible for the third step of PPP, the oxidative carboxylation?

A

6-phosphogluconate dehydrogenase

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29
Q

What is an extra product of the third step of PPP, besides the ribulose 5 phosphate and NADPH?

A

CO2 (carbon dioxide)

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30
Q

In which two steps of PPP is NADPH made?

A

Step one - dehydrogenation & step three - oxidative decarboxylation

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31
Q

In which step of PPP is a glycolysis like intermediate made?

A

Step four - isomerization

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32
Q

If there is low energy in the cell, where are the intermediates of PPP, such as G3P, going to go?

A

Glycolysis (to make energy)

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33
Q

What do the fat synthesis and cholesterol pathways use up that eventually stimulates PPP?

A

NADPH

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34
Q

What enzymes make up the reversible reactions of PPP that provide linkages with this pathway and glycolysis?

A

Transketolases and transaldolases

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35
Q

What is reductive biosynthesis?

A

Building things by adding electrons (donated from NADPH) like fat, cholesterol, steroid hormones, bile salts

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36
Q

Where in fat synthesis is NADPH used?

A

Reductions steps of “CRDR” (fatty synthase)

37
Q

What is the process of detoxification?

A

Making toxins more water soluble for excretion through the urine by adding electrons (from NADPH)

38
Q

What is added to toxins during detoxification to make them more water soluble?

A

Hydroxyl groups (OH)

39
Q

What system of enzymes is used for detoxification?

A

The liver’s P450 monooxygenase system

40
Q

What other substance must join with the extra electrons from NADPH to make toxins more water soluble?

A

O2 (oxygen) to make the final OH group

41
Q

Where is the location of the cytochrome P450 monooxygenase system?

A

Endoplasmic reticulum of the liver

42
Q

The cytochrome p450 monooxygenase system adds hydroxyl groups to what types of compounds?

A

Aromatic and aliphatic

43
Q

What is respiratory burst?

A

Creating “harsh chemistry” by using electrons from NADPH to kill off non-self things like bacteria

44
Q

Why is it called respiratory burst?

A

White blood cells take in more oxygen

45
Q

What reactive molecules are made during respiratory burst to kill off bacteria in a vesicle?

A

Oxygen and electrons from NADPH

46
Q

What enzyme makes hypochlorus acid (HOCl) from hydrogen peroxide during respiratory burst?

A

Myeloperoxidase

47
Q

What other molecule is made during respiratory burst to kill off bacteria?

A

H2O2 (hydrogen peroxide)

48
Q

What enzyme in respiratory burst changes O2- to H2O2?

A

Superoxide dismutase

49
Q

What is antioxidant regeneration?

A

Adding electrons (from NADPH) to antioxidants to keep them protecting the body from free radicals

50
Q

What has the ability to inactivate reactive molecules?

A

Antioxidants

51
Q

What is an antioxidant?

A

A substance that inhibits oxidation and is capable of counteracting the damaging effects of oxidation in body tissue

52
Q

What is a free radical?

A

An atom or molecule that has one or more unpaired electrons

53
Q

What types of free radicals are referred to as ROS or RNS?

A

Those containing oxygen or nitrogen

54
Q

What does ROS stand for?

A

Reactive oxygen species

55
Q

What does RNS stand for?

A

Reactive nitrogen species

56
Q

Do reactive species always have to be free radicals?

A

No

57
Q

Are free radicals always reactive species?

A

Yes

58
Q

What is O2-?

A

Superoxide

59
Q

What is e-OH?

A

Hydroxyl

60
Q

Is hydrogen peroxide considered a radical?

A

No, but it is a reactive species

61
Q

Why are free radicals and reactive species bad?

A

They attack polyunsaturated fat in phospholipids, attack protein in cells, and attack nucleic acids in DNA

62
Q

What is quenching in reference to reactive species?

A

The process by which electronically excited molecules are inactivated

63
Q

How is quenching usually established?

A

By an antioxidant giving an electron to a free radical

64
Q

Antioxidant regeneration give what power back to the antioxidant?

A

Reducing power

65
Q

When antioxidants are being regenerated, are they being oxidized or reduced?

A

Reduced; electrons are being added to them

66
Q

During antioxidant regeneration, is NADPH being oxidized or reduced?

A

Oxidized

67
Q

What else may quench free radicals?

A

Enzymes such as superoxide dismutase, catalase, and glutathione peroxidase

68
Q

What does catalase quench specifically?

A

Hydrogen peroxide

69
Q

What is the location of superoxide dismutase?

A

Extracellular, cytoplasm, mitochondria

70
Q

What is the function of superoxide dismutase?

A

Eliminate superoxide and produce hydrogen peroxide

71
Q

What is the extra product of the reaction with superoxide dismutase creating hydrogen peroxide?

A

O2

72
Q

Superoxide dismutase requires what cofactors?

A

Zinc and copper (along with manganese in the mitochondria)

73
Q

What is formed when an electron is added to a superoxide radical?

A

Molecular oxygen

74
Q

Where is O2- created?

A

Catecholamine/oxygen reactions, folate or THF/oxygen reactions, mitochondrial production (ETC), cytochrome p450, and white blood cells

75
Q

Is O2- lipid soluble?

A

No; therefore, it does not travel far from the site of production

76
Q

How is O2- created in the mitochondria during ETC?

A

Due to leakage of electrons from coenzymeQ to O2

77
Q

What can increase the effect of superoxide formation during the ETC?

A

Exercise

78
Q

What is the location of catalase?

A

Mostly in cell peroxisomes; smaller amounts in the cytoplasm, mitochondria, and microsomes

79
Q

What is the function of catalase?

A

Eliminates hydrogen peroxide

80
Q

What type of cell has a lot of catalase?

A

Neutrophils (respiratory bursts)

81
Q

What occurs in cell peroxisomes?

A

Oxidation of very long fatty acids

82
Q

What is a cofactor of catalase?

A

Iron

83
Q

What is the end result of catalase on hydrogen peroxide?

A

Water and oxygen

84
Q

Most hydrogen peroxide is removed by what enzyme?

A

Glutathione peroxidase

85
Q

Where is glutathione peroxidase located?

A

Cytosol and mitochondria

86
Q

What is the cofactor of glutathione peroxidase?

A

Selenium

87
Q

What reactive species does glutathione peroxidase quench?

A

Hydrogen peroxide

88
Q

What is used to regenerate glutathione peroxidase?

A

Electrons from NADPH and the enzyme glutathione reductase

89
Q

Because NADPH is needed for antioxidant regeneration, what enzyme is therefore stimulated?

A

Glucose 6 phosphate dehydrogenase

Biochemistry II Final (5 decks)

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