Hexose Monophospahte Pathway

Question 1

The Hexose Monophosphate Pathway (HMP) begins with

Answer 1

Glucose-6-Phosphate

Question 2

HMP’s principal purpose is the production of the cell’s basic anabolic reducing power, reduced

Answer 2

NADPH

Question 3

The secondary purpose of the HMP is the synthesis of

Answer 3

Ribose-5-Phosphate (R5P)

Question 4

Seven, six, five and four carbon compounds are

Answer 4

HMP intermediates

Question 5

These sugar intermediates can enter the pathway directly from the diet, as well via G6P and by salvage of pentoses produced by catabolism of cellular constituents such as

Answer 5

Nucleotides and Glucuronic Acid

Question 6

Likewise, these intermediates may be siphoned off for other biosynthetic purposes. Their principal fate is as precursors in

Answer 6

Glycolysis

Question 7

The primary mechanism for the regulation of this pathway involves the cell’s need for

Answer 7

NADPH

Question 8

The primary mechanism for the regulation of this pathway involves the cell’s need for NADPH, exerting its effect upon the first enzyme in the pathway

Answer 8

G-6-P Dehydrogenase

Question 9

Takes place in the cytoplasm of all cell types

Answer 9

HMP

Question 10

Because there are alternative routes for R5P synthesis, most pathology associated with defects in this pathway are attributable to a diminished supply of

Answer 10

Reducing Power (NADPH)

Question 11

What are the two phases to the HMP?

Answer 11

1. ) Oxidative Phase

2. ) Non-oxidative (sugar-interconversion) phase

Question 12

Neither phase utilizes

Answer 12

ATP

Question 13

There are three irreversible steps in the oxidative phase, followed by the isomerization of ribulose 5-phosphate to

Answer 13

Ribose-5-Phosphate

Question 14

It is the #1 carbon of G6P that is recovered as

Answer 14

CO2

Question 15

Unless the cell requires R5P as precursor for other specific biosynthetic processes it is further metabolized by a series of sugar interconversions, ultimately producing precursors for glycolysis in the

Answer 15

Non-oxidative phase

Question 16

The reactions catalyzed in the nonoxidative phase are all

Answer 16

Reversible

Question 17

In the non-oxidative phase, Ribulose 5-P is isomerized to produce ribose 5-P, and it is also epimerized to produce

Answer 17

Xylulose 5-P

Question 18

After three additional reactions, first with a transketolase, then a transaldolase, and concluding with again with transketolase, we arrive at

Answer 18

Glycolysis intermediates

Question 19

Which two glycolysis intermediates does the non-oxidative phase produce?

Answer 19

Glyceraldehyde-3-phosphate and fructose-6-phosphate

Question 20

The starting material for the HMP is

Answer 20

3 moles of G-6-P

Question 21

What are the 4 end products of the HMP?

Answer 21

1. ) 3 CO2
2. ) 6 NADPH
3. ) 2 F-6-P
4. ) 1 Glyceraldehyde-3-P

Question 22

When the cell needs more NADPH than it does R-5-P, we use the glyceraldehyde and F-6-P products to synthesize

Answer 22

G-6-P

Question 23

This G-6-P can be used to produce how many NADPH

Answer 23

12

Question 24

This is a likely scenario in cells where there is a considerable need for NADPH, such as in the synthesis of

Answer 24

Fatty Acids

Question 25

When the cell needs equal amounts of NADPH and R-5-P, what happens?

Answer 25

HMP "halts" with conclusion of oxidative phase

Question 26

In this scenario, no sugar interconversions occur because R5P is utilized in other processes before it can be acted on by

Answer 26

Transketolase

Question 27

This might commonly occur in rapidly dividing cells with the need to replicate the genomic material

Answer 27

Needing more R-5-P than NADPH

Question 28

Because the sugar-interconversion reactions are reversible, it is possible to synthesize R5P from

Answer 28

Glycolytic Intermediates

Question 29

What happens when the cell requires more NADPH than it does R5P but does not have the luxury of performing gluconeogenesis (I.e. the cell needs more ATP)?

Answer 29

In this case the sugar-interconversion phase fully converts R5P to glycolytic precursors

Question 30

Sometimes, the cell needs more NADPH than it does R-5-P but it can not undergo gluconeogenesis. In this case the sugar-interconversion phase fully converts R5P to glycolytic precursors which then act as substrate in the

Answer 30

TCA cycle

Question 31

This occurs via pyruvate, with the concamitant synthesis of

Answer 31

2 moles ATP per mole of acetyl-CoA

Question 32

The rate limiting step in the HMP is the first one, catalyzed by

Answer 32

Glucose-6-phosphate Dehydrogenase (G6PDH)

Question 33

G6PDH is, in the short term, principally regulated in a negative feedback manner by

Answer 33

NADPH

Question 34

Long term regulation occurs at the level of transcription of the gene encoding G6PDH, and is influenced positively by

Answer 34

Insulin

Question 35

The cell’s principal currency in anabolic reducing power

Answer 35

NADPH

Question 36

Its synthesis is the basis for our dietary requirement for

Answer 36

Niacin/Nicotinamide

Question 37

Able to donate TWO so-called reducing equivalents

Answer 37

NADPH

Question 38

In contrast to NADH, made during glycolysis and the TCA cycle and used in the process of oxidative phosphorylation, NADPH is NOT associated with

Answer 38

Oxidative Phosphorylation or ATP synthesis

Question 39

Required in several phases of fatty acid synthesis

Answer 39

NADPH

Question 40

Production of the major product of fatty acid synthesis, palmitate, a 16 carbon fatty acid requires

Answer 40

14 molecules of NADPH

Question 41

Required at two different points in the process of cholesterol biosynthesis

Answer 41

NADPH

Question 42

The synthesis of mevalonate from 3-hydroxy-3-methylglutaryl CoA requires

Answer 42

2 NADPH

Question 43

Hydroxylation of cholesterol to certain steroid hormones also requires NADPH, in a process involving the

Answer 43

P-450 System

Question 44

Conversion of the ribose unit of nucleotides to the deoxyribose form is a multi-step process that begins with

Answer 44

NADPH

Question 45

Ribose is converted to deoxyribose by the enzyme

Answer 45

Ribonucleotide reductase

Question 46

NADPH is also required for the conversion of

Answer 46

dUMP to dTMP

Question 47

Over 100 isozymes are members of this “superfamily” of mono-oxygenases with specificities for the oxidation of steroids, carcinogens, drugs or xenobiotic substances

Answer 47

Cytochrome P-450 enzymes

Question 48

The aim of the P-450 system is to recognize, solubilize and thereby promote the removal of such foreign materials from the body via

Answer 48

The Kidneys

Question 49

A variety of chemical transformations are possible among the array of P-450 enzymes, but they all have in common the reaction of a single oxygen with either a

Answer 49

Carbon, Sulfur, or Nitrogen

Question 50

What is NADPH's role in the P-450 system?

Answer 50

Reduces iron from Fe3+ to Fe2+ at two points in the cycle

Question 51

Reducing power is transferred to the cytochrome by an intermediary called the -a membrane bound enzyme

Answer 51

NADPH-Cytochrome P-450 reductase

Question 52

The P-450 system functions best with substrates with some

Answer 52

Hydrophobicity

Question 53

In addition to functioning in drug and xenobiotic removal, specific P-450 enzymes are used in the biosynthesis of

Answer 53

Steroid Hormones

Question 54

Catalyzes a reaction from cigarette smoke that is actually dangerous to humans

Answer 54

P-450 system

Question 55

The chemical process by which granulocytes (macrophages, neutrophils and eosinophils) destroy invading microorganisms is initiated by

Answer 55

NADPH oxidase

Question 56

Forms superoxide form NADPH and O2

Answer 56

NADPH oxidase

Question 57

NADPH oxidase forms superoxide (a free-radical form of oxygen) from NADPH and O2 with the consumption of O2. This is referred to as a

Answer 57

Respiratory Burst

Question 58

Converts superoxide to hydrogen peroxide

Answer 58

Superoxide dismutase

Question 59

Genetic defects in the NADPH oxidase leads to -Reduces the hosts ability to fight bacterial infections

Answer 59

Granulomatous Disease

Question 60

A tripeptide present in high concentrations in all cell types and functions to protect cellular components from the reactive peroxides

Answer 60

Glutathione

Question 61

Reduced glutathione (GSH) reacts with peroxide to form

Answer 61

Water

Question 62

Regeneration of GSH requires NADPH and the enzyme

Answer 62

Glutathione reductase

Question 63

Catalyzes the conversion of arginine and O2 to citruline and NO, requiring one NADPH in the process

Answer 63

NO-synthetase

Question 64

This pathway possibly accounts for a considerable portion of the body’s use of

Answer 64

NADPH

Question 65

One of the precursors in the biosynthesis of aromatic amino acids

Answer 65

Erythrose 4-phosphate

Question 66

A prosthetic group in the transketolase functioning in the non-oxidative phase of the HMP

Answer 66

Thiamine Pyrophosphate (TPP)

Question 67

Covalently bound to the two carbon unit that is exchanged in the transketolase reaction

Answer 67

TPP

Question 68

Transketolase that lacks TPP is

Answer 68

Inactive

Question 69

Individuals harboring mutations in transketolase that reduce its affinity for TPP can display a series of symptoms that are in aggregate referred to as the

Answer 69

Wernicke-Korsakoff Syndrome (WKS)

Question 70

In large part, the symptomology is neurological, ranging from depression, irritability and fatigue to

Answer 70

Confusion, ataxia, and opthalmoplegia

Question 71

Most commonly seen in chronic alcoholics, presumably due to poor absorption of the vitamin

Answer 71

Wernicke-Korsakoff Syndrome (WKS)

Question 72

Represents the most prevalent enzymopathy in human populations, where as many as 400 million people world wide are deficient

Answer 72

G6PDH Deficiency

Question 73

10-25% of tropical African populations, 1-3% of some Mediterranean populations, and 5-10% of tropical and sub-tropical Asian populations are affected by

Answer 73

G6pDH deficiency

Question 74

Defects in transketolase do not have an immediate influence upon the production of

Answer 74

NADPH

Question 75

However, defects in G6PDH drastically affect the production of

Answer 75

NADPH

Question 76

G6PDH deficiency presents as a form of

Answer 76

Hemolytic anemia

Question 77

Can be induced by the ingestion of the fava bean

Answer 77

G6PDH

Question 78

Deficiency for G6PDH in red blood cells (RBC) severely restricts its ability to generate

Answer 78

NADPH

Question 79

When ROS build up in RBCs they can react with hemoglobin, which results in the precipitation of

Answer 79

Heinz bodies

Question 80

The G6PDH gene is located on the

Answer 80

X-chromosome

Question 81

An example of a class IV enzyme; it shows an alteration in electrophoretic mobility, but no significant difference in its enzymatic properties

Answer 81

G6PDH A variant

Question 82

More severe, and do show clinical symptoms, albeit rarely and under specific circumstances

Answer 82

Class III mutations

Question 83

A member of class III mutations

Answer 83

G6PDH A- varient

Question 84

Higher up on the scale of severity is the G6PD Mediterranean, categorized in

Answer 84

Class II

Question 85

The Mediterranean variant shows normal enzyme activity, but is present in much reduced levels in the

Answer 85

RBC

Question 86

Lastly, class I mutations are the most severe, with chronic anemia. These most severe deficiencies in G6PDH activity have a condition called

Answer 86

Nonspherocytic anemia

Question 87

There is a link between the presence of mutations in G6PDH and resistance to

Answer 87

Malaria

Question 88

Ironically, individuals with G6PDH deficiency may show the characteristic hemolytic response to the anti-malarial drug

Answer 88

Primaquine

Question 89

In lipid synthesizing cells of the adipose, mammary gland and liver as much as 70% of the NADPH produced comes from the so-called -The reason G6PDH deficiency does not always show severe symptoms

Answer 89

Malic Enzyme

Question 90

NADPH can also be produced from NADH in the mitochondrion, by means of

Answer 90

Nicotinamide Nucleotide Transhydrogenase