Pentose Phosphate Pathway

Question 0

What is the main enzyme in PPP?

Answer 0

Glucose 6 phosphate dehydrogenase

Question 1

What does PPP start with?

Answer 1

Glucose 6 phosphate

Question 2

What is made in the PPP?

Answer 2

Ribose and NADPH

Question 3

Where is the PPP located in the cell?

Answer 3

Cytosol

Question 4

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

Answer 4

2

Question 5

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

Answer 5

Ribose 5 phosphate

Question 6

What is another named for the PPP?

Answer 6

Hexose monophosphate pathway

Question 7

Is ATP produced or consumed in the PPP?

Answer 7

Neither! (Unique)

Question 8

What are the two purines?

Answer 8

Guanine and adenine

Question 9

What are the two pyrimidines?

Answer 9

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

Question 10

What is a nucleoside?

Answer 10

Nitrogenous base + sugar

Question 11

What is a nucleotide?

Answer 11

Nitrogenous base + sugar + phosphate

Question 12

What do we need ribose 5 phosphate for?

Answer 12

ATP, coenzyme A, NAD, FAD, nucleic acids

Question 13

What stimulates PPP overall?

Answer 13

Anything that consumes ribose 5 phosphate

Question 14

What do we use NADPH for?

Answer 14

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

Question 15

Is NADPH an electron donor or acceptor?

Answer 15

Donor

Question 16

Is the first irreversible reaction of PPP oxidative or reductive?

Answer 16

Oxidative

Question 17

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

Answer 17

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

Question 18

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

Answer 18

Glucose 6 phosphate

Question 19

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

Answer 19

6 phosphate gluconate alpha lactone (6-phosphogluconolactone)

Question 20

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

Answer 20

Occurs to 6-P gluconate to yield ribulose 5 phosphate

Question 21

What occurs in the fourth isomeric action step in PPP?

Answer 21

Ribulose 5 phosphate to ribose 5 phosphate

Question 22

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

Answer 22

Glucose 6 phosphate and NADP+

Question 23

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

Answer 23

NADPH

Question 24

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

Answer 24

Glucose 6 phosphate dehydrogenase (main enzyme of PPP)

Question 25

What effect does NADPH have on glucose 6 phosphate dehydrogenase?

Answer 25

Inhibition (because it's a product)

Question 26

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

Answer 26

Lactonase

Question 27

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

Answer 27

H20 (water)

Question 28

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

Answer 28

6-phosphogluconate dehydrogenase

Question 29

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

Answer 29

CO2 (carbon dioxide)

Question 30

In which two steps of PPP is NADPH made?

Answer 30

Step one - dehydrogenation & step three - oxidative decarboxylation

Question 31

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

Answer 31

Step four - isomerization

Question 32

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

Answer 32

Glycolysis (to make energy)

Question 33

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

Answer 33

NADPH

Question 34

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

Answer 34

Transketolases and transaldolases

Question 35

What is reductive biosynthesis?

Answer 35

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

Question 36

Where in fat synthesis is NADPH used?

Answer 36

Reductions steps of "CRDR" (fatty synthase)

Question 37

What is the process of detoxification?

Answer 37

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

Question 38

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

Answer 38

Hydroxyl groups (OH)

Question 39

What system of enzymes is used for detoxification?

Answer 39

The liver's P450 monooxygenase system

Question 40

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

Answer 40

O2 (oxygen) to make the final OH group

Question 41

Where is the location of the cytochrome P450 monooxygenase system?

Answer 41

Endoplasmic reticulum of the liver

Question 42

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

Answer 42

Aromatic and aliphatic

Question 43

What is respiratory burst?

Answer 43

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

Question 44

Why is it called respiratory burst?

Answer 44

White blood cells take in more oxygen

Question 45

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

Answer 45

Oxygen and electrons from NADPH

Question 46

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

Answer 46

Myeloperoxidase

Question 47

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

Answer 47

H2O2 (hydrogen peroxide)

Question 48

What enzyme in respiratory burst changes O2- to H2O2?

Answer 48

Superoxide dismutase

Question 49

What is antioxidant regeneration?

Answer 49

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

Question 50

What has the ability to inactivate reactive molecules?

Answer 50

Antioxidants

Question 51

What is an antioxidant?

Answer 51

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

Question 52

What is a free radical?

Answer 52

An atom or molecule that has one or more unpaired electrons

Question 53

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

Answer 53

Those containing oxygen or nitrogen

Question 54

What does ROS stand for?

Answer 54

Reactive oxygen species

Question 55

What does RNS stand for?

Answer 55

Reactive nitrogen species

Question 56

Do reactive species always have to be free radicals?

Answer 56

No

Question 57

Are free radicals always reactive species?

Answer 57

Yes

Question 58

What is O2-?

Answer 58

Superoxide

Question 59

What is e-OH?

Answer 59

Hydroxyl

Question 60

Is hydrogen peroxide considered a radical?

Answer 60

No, but it is a reactive species

Question 61

Why are free radicals and reactive species bad?

Answer 61

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

Question 62

What is quenching in reference to reactive species?

Answer 62

The process by which electronically excited molecules are inactivated

Question 63

How is quenching usually established?

Answer 63

By an antioxidant giving an electron to a free radical

Question 64

Antioxidant regeneration give what power back to the antioxidant?

Answer 64

Reducing power

Question 65

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

Answer 65

Reduced; electrons are being added to them

Question 66

During antioxidant regeneration, is NADPH being oxidized or reduced?

Answer 66

Oxidized

Question 67

What else may quench free radicals?

Answer 67

Enzymes such as superoxide dismutase, catalase, and glutathione peroxidase

Question 68

What does catalase quench specifically?

Answer 68

Hydrogen peroxide

Question 69

What is the location of superoxide dismutase?

Answer 69

Extracellular, cytoplasm, mitochondria

Question 70

What is the function of superoxide dismutase?

Answer 70

Eliminate superoxide and produce hydrogen peroxide

Question 71

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

Answer 71

O2

Question 72

Superoxide dismutase requires what cofactors?

Answer 72

Zinc and copper (along with manganese in the mitochondria)

Question 73

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

Answer 73

Molecular oxygen

Question 74

Where is O2- created?

Answer 74

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

Question 75

Is O2- lipid soluble?

Answer 75

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

Question 76

How is O2- created in the mitochondria during ETC?

Answer 76

Due to leakage of electrons from coenzymeQ to O2

Question 77

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

Answer 77

Exercise

Question 78

What is the location of catalase?

Answer 78

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

Question 79

What is the function of catalase?

Answer 79

Eliminates hydrogen peroxide

Question 80

What type of cell has a lot of catalase?

Answer 80

Neutrophils (respiratory bursts)

Question 81

What occurs in cell peroxisomes?

Answer 81

Oxidation of very long fatty acids

Question 82

What is a cofactor of catalase?

Answer 82

Iron

Question 83

What is the end result of catalase on hydrogen peroxide?

Answer 83

Water and oxygen

Question 84

Most hydrogen peroxide is removed by what enzyme?

Answer 84

Glutathione peroxidase

Question 85

Where is glutathione peroxidase located?

Answer 85

Cytosol and mitochondria

Question 86

What is the cofactor of glutathione peroxidase?

Answer 86

Selenium

Question 87

What reactive species does glutathione peroxidase quench?

Answer 87

Hydrogen peroxide

Question 88

What is used to regenerate glutathione peroxidase?

Answer 88

Electrons from NADPH and the enzyme glutathione reductase

Question 89

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

Answer 89

Glucose 6 phosphate dehydrogenase