Pentose Phosphate Pathway and NADPH

Question 1

Other name for the Pentose Phosphate Pathway

Answer 1

Hexose MonoPhosphate (HMP) shunt

Question 2

This pathway is a branch off of the

Answer 2

glycolytic pathway

Question 3

The two main purposes of this pathway are:

Answer 3

1. Generation of NADPH

2. Generation of the 5-C sugar ribose (to be used in synthesis of nucleotides)

Question 4

Depending on the needs of the cell, the pathway can produce:

Answer 4

Either:
-both ribose and NADPH
or
-either NADPH or ribose

Question 5

The net total ATP used and produced in this pathway is

Answer 5

zero; none are produced or used

Question 6

Name the Oxidative Irreversible Reactions of HMP

Answer 6

Step 1: Dehydrogenation of Glucose 6-P
Step 2: Hydrolysis to 6-phosphogluconate
Step 3: Oxidative decarboxylation of 6-phosphogluconate

Question 7

Name the enzyme responsible for Step 1 of the Oxidative Irreversible Reaction:

Answer 7

Glucose 6-phosphate dehydrogenase (G6PD)

Question 8

Which step within the Oxidative Irreversible Reactions of HMP is the rate-limiting step?

Answer 8

Step 1: Dehydrogenation of Glucose 6-P

Question 9

Which enzyme within the Oxidative Irreversible Reactions requires NADP+ as a coenzyme?

Answer 9

Glucose 6-phosphate dehydrogenase (G6PD)

Question 10

What molecule is a potent competitive inhibitor within Step 1 of the Oxidative Irreversible Reactions?

Answer 10

NADPH

Question 11

Expression of G6PD is upregulated by

Answer 11

insulin

Question 12

The flux of G6PD through the pathway is increased in the

Answer 12

absorptive state

Question 13

Name the enzyme responsible for Step 2 of the Oxidative Irreversible Reaction:

Answer 13

6-phosphogluconolactone hydrolase

Question 14

Name the enzyme responsible for Step 3 of the Oxidative Irreversible Reaction:

Answer 14

6-phosphogluconate dehydrogenase

Question 15

Which steps within the HMP pathway are irreversible?

Answer 15

Steps 1-3: Oxidative Irreversible Reactions

1. Dehydrogenation of Glucose 6-P
2. Hydrolysis to 6-phosphogluconate
3. Oxidative decarboxylation of 6-phosphogluconate

Question 16

Steps 4-8 of the HMP pathway are considered the

Answer 16

Nonoxidative Reversible Reactions

Question 17

Steps 4-8 are responsible for

Answer 17

Interconversions of sugar molecules

Question 18

Describe the Nonoxidative reversible reactions within HMP:

Answer 18

• reversible steps
• interconvert sugars w/3-7 C-atoms
• permit synthesis of ribose 5-P used for nucleotide production

Question 19

The enzyme responsible for steps 4-8 of HMP is:

Answer 19

Transketolase

Question 20

This enzyme requires TPP from thiamine

Answer 20

Transketolase

Question 21

Transketolase is important for

Answer 21

diagnosing thiamine deficiency

Question 22

Name the functions of NADPH:

Answer 22

1. Electron donor for the “reductive” biosynthesis of fatty acids, cholesterol, steroids
2. Electron donor for neutralization of reactive oxygen species
3. Provides reducing equivalents for Cytochrome P450 Monooxygenase system (for biosynthesis of steroids, detox xenobiotics)
4. Play role in phagocytosis (destruction of pathogens by macrophages and neutrophils)
5. Substrate for synthesis of nitric oxide (NO)

Question 23

When are reactive oxygen species produced?

Answer 23

During aerobic metabolism, through reactions with drugs and toxins, when levels of antioxidants are diminished

Question 24

____ is the major antioxidant system

Answer 24

Glutathion (GSH/GSSG)

Question 25

_____ is an enzyme that will incorporate 1 O-atom from molecular oxygen (creating -OH group) w/the other being reduced to H2O.

Answer 25

Monooxygenase

Question 26

Cyt P450 systems:

_____ system: the synthesis of steroids

Answer 26

Mitrochondrial

Question 27

Cyt P450 systems:

_____ system: detoxification of foreign compounds

Answer 27

Microsomal

Question 28

This Cyt P450 system is associated with the inner mitochondrial membrane.

Answer 28

Mitochondrial Cytochrome P450

Question 29

Mitochondrial Cytochrome P450 in the liver

Answer 29

uses the same system to synthesize bile acids and Vitamin D3

Question 30

Mitochondrial Cytochrome P450 in the kidney

Answer 30

converts vitamin D3 to its active form

Question 31

Mitochondrial Cytochrome P450 in steroidogenic tissues (placenta, ovaries, testes and adrenal cortex)

Answer 31

uses NADPH for synthesis of steroid hormones

Question 32

This Cyt P450 system is associated with the membranes of the smooth ER in liver cells

Answer 32

Microsomal system Cytochrome P450

Question 33

This system is responsible for the detoxification of drugs, toxins and other chemicals.

Answer 33

Microsomal System Cytochrome P450

Question 34

In the microsomal system cytochrome p450, by adding ____, the compound may be inactivated (or activated), made more soluble, or provide a reactive group for attachment of other molecules.

Answer 34

oxygen (hydroxyl groups)

Question 35

NADPH plays a role in phagocytosis within these cells

Answer 35

White Blood Cells (neutrophils and macrophages)

Question 36

NADPH role in phagocytosis:

-generates ______ that aid in killing microorganisms they have engulfed.

Answer 36

oxygen free radicals

Question 37

The MPO system is a combination of:

Answer 37

NADPH oxidase and myeloperoxidase

Question 38

The MPO system is used to

Answer 38

generate oxygen free radicals to aid in destruction of microorganisms

Question 39

Rare genetic NADPH oxidase deficiency causes

Answer 39

Chronic Granulomatous Disease (CGS)

Question 40

The granuloma in ____ is formed as a defense where the body attempts to “wall off” the collection of cells from the rest of the body

Answer 40

CGS: Chronic Granulomatous Disease

Question 41

CGS causes

Answer 41

persistent severe infections due to the inability to kill bacteria forming granulomas

Question 42

___ is synthesized from arginine, oxygen and NADPH

Answer 42

NO (Nitric Oxide)