Hexose Monophosphate Pathway

Question 1

Where in the cell does the hexose monophosphate pathway (also known as: pentose phosphate pathway) occur?

Answer 1

Cytoplasm

Question 2

What is the major product of the oxidative pathway?

What is the major product of BOTH pathways?

Answer 2

• Main product of oxidative pathway = NADPH
• Main product of both pathways = Ribose

Question 3

True or False: The hexose monophosphate pathway produces ATP

Answer 3

False - it does NOT

Question 4

Which pathway generates NADP and 5 carbon monosaccharides?

Answer 4

Oxidative Pathway

Question 5

Overall reaction of the oxidative pathway?

Answer 5

Reactant: Glucose-6-Pi + 2NADP+ and water

Product: Ribose-5-Pi + CO2 + 2 NADPH + H+

Question 6

What enzyme is involved in the committed, irreversible step of the oxidative pathway?

Answer 6

Glucose 5 phosphate dehydrogenase

Question 7

What is the committed, irreversible step of the oxidative pathway? Product?

Answer 7

Glucose-6-phosphate -> 6-phosphoglucono-delta-lactone

(NADP+ -> NADPH)

Question 8

Which enzyme in oxidative pathway produces and is inhibited by NADPH?

Answer 8

Glucose-6-phosphate dehydrogenase

Question 9

In the second step of the oxidative pathway, _____ is converted to ______ using _____ (also known as glucanolactonase).

What is consumed in reaction?

Answer 9

6-phosphoglucono-delta-lactone ->
6-phosphogluconate

Enzyme: 6-phosphogluconolactone hydrolase

1 water molecule is consumed

Question 10

How many steps in the oxidative pathway are reversible? Irreversible?

Answer 10

Reversible - 2 (including isomerase reaction)
Irreversible - 2

Question 11

At what stages of the oxidative pathway is NADPH generated?

Answer 11

Step 1 and Step 3

Question 12

Third step of the oxidative pathway?
Products?

Answer 12

6 phosphogluconate -> ribulose-5-Pi + CO2
Enzyme: 6-phosphogluconoate dehydrogenase

Products: CO2 + NADPH

Question 13

In the 4th step of the oxidative pathway,
ribulose 5-phosphate is interconverted between ribose-5-phosphate using which enzyme?

Is this stage irreversible or reversible?

Answer 13

Isomerase
- Reversible

Question 14

_____ is an isomer that is important for DNA synthesis

Answer 14

ribose-5-phosphate

Question 15

____is an important isomer for the body and is created in the final stage of the oxidative pathway

Answer 15

xyulose-5-phosphate

Question 16

In the final stage of the oxidative pathway, ___ is converted to ____

What enzyme is required?

Answer 16

ribulose-5-phosphate <-> xyulose-5-P

Epimeriase

Question 17

The ratio of _____:____ regulates the committed step of the oxidative pathway

Answer 17

NADPH/NADP+

Question 18

When the cell needs more NADPH, the ratio of ___ decreases and flux through pathway ___

Answer 18

decreases; increases

Question 19

How does insulin affect expression of G6PD gene in the liver? How does it affect flux through the pathway after a meal?

Answer 19

Insulin upregulates the expression of G6PD in the liver

Increases flux through pathway after a meal

Question 20

What organ is the major site of fatty acid biosynthesis?

Answer 20

Liver

Question 21

Which pathway makes 5C monosaccharide (ribose) withouts without making NADPH?

Answer 21

Non-Oxidative pathway

Question 22

True or False: The Non-Oxidative Branch of the pentose phosphate pathway has enzymes found in all cells that make nucleotides (note: all cells need nucleotides, such as ATP, to some extent)

Answer 22

True

Question 23

In the Non-Oxidative Pathway ___ is converted to ___ and ____

Answer 23

3-ribose-5-phosphate =>
2 fructose 6-Pi + 3-glyceraldehyde-3-Pi

Question 24

The non-oxidative pathway uses three enzymes, but two key ones are ____ and ___

Answer 24

transketolase + transaldolase

Question 25

_____ transfers 2C group and requires thiamine ____transfers 3C group

Answer 25

Transketolase Transaldolase

Question 26

What is the first step of the non-oxidative pathway?

Answer 26

Ribulose-5-P <--> xyulose-5-P Via: phosphopentose epimerase

Question 27

In step 2 of non-oxidative pathway, transketolase takes 2 carbons off of ____ and donates them to _____ What does this yield?

Answer 27

xyulose-5-P ; ribose-5-P Yields: Glyceraldehyde-3-P +Seduoheptulase 7-Pi

Question 28

______, a product of stage 2 (non-oxidative pathway), is a glycolysis intermediate

Answer 28

Glyceraldehyde-3-P

Question 29

Stage 3 of the non-oxidative pathway involves _____, an enzyme, pulling 3 carbons off of ____ and adding them to ______ to yield ____+_____

Answer 29

Transaldolase; seduoheptulase-7-P; glyceraldehyde-3-P = erythrose-4-P + fructose-6-Pi

Question 30

____, a product of stage 3 non-oxidative pathway, is a glycolysis intermediate

Answer 30

fructose-6-Pi

Question 31

In stage 4 of the non-oxidative pathway, ____, an enzyme, removes 2 carbons off of ___ and adds them to ___, yielding ___ and ____

Answer 31

Transketolase; Xyulose-5-P ; Erythrose-4-Pi = Glyceraldehyde-3-P + Fructose-6-P (both are intermediates in glycolysis)

Question 32

What two factors regulate the non-oxidative branch?

Answer 32

Level of substrates and needs of the cell

Question 33

True or False: For the non-oxidative branch, you can make use ribose-P to make glycolytic intermediates or vice versa

Answer 33

True

Question 34

NADPH is important for synthesis of ___, ___, and ____

Answer 34

fatty acids, cholesterol, steroids

Question 35

True or False: Biosynthetic reactions that involve oxidation require NADPH

Answer 35

False - Biosynthetic reactions that involve REDUCTION require NADPH (carries 1 H+ and 2e-) Generates NADP as a product

Question 36

Biosynthetic pathways that make NADPH are found in the ____, ____, ____, ____, and ____

Answer 36

liver, adrenal gland, testes, ovaries

Question 37

Synthesis of ___ requires NADPH

Answer 37

NO

Question 38

L-Arginine is converted to L-Citrulline using NO Synthase and ____. As a result, ___ is made

Answer 38

NADPH; NO

Question 39

Roles of NO?

Answer 39

1) Relaxes smooth muscle 2) Brain NT 3) Regulates macrophages 4) Prevents platelet aggregation

Question 40

Maintaining reduced glutathione requires ____

Answer 40

NADPH

Question 41

What three molecules make up glutathione?

Answer 41

1) Glycine 2) Cysteine 3) y-glutamate

Question 42

GSSG = ? GSH = ?

Answer 42

GSSG = oxidized glutathione GSH = reduced glutathione

Question 43

Reduced glutathione (GSH) reacts with ___ and other organic peroxides to prevent cellular damage

Answer 43

H2O2 - neutralizes damage potential

Question 44

_____ is a good reducing agent for detoxification

Answer 44

Reduced glutathione

Question 45

_____ GSH keeps amino acid side chains in proteins reduced. It keeps them from oxidizing and forming wrong disulfide bonds.

Answer 45

Sulfhydryl buffer

Question 46

Glutathione Reductase is an enzyme that uses NADPH to generate ___ from ___

Answer 46

GSH ; GSSG