HMP SHUNT

Question 1

What is HMP shunt?

Answer 1

Serves as an alternative path for glucose and G-6-P is shunted away from glycolysis

Question 2

Where is the HMP shunt located?

Answer 2

Lactating mammary glands, liver, adrenal cortex, RBCs

Question 3

What are the other names for HMP shunt?

Answer 3

Pentose phosphate pathway or 6 phosphogluconate pathway

Question 4

Where does this pathway take place?

Answer 4

Cytosol

Question 5

Oxidative reactions are ___ and ____

Answer 5

Irreversible and Rate limiting

Question 6

Non-oxidative reactions are ___

Answer 6

Reversible

Question 7

Which substrates are oxidative?

Answer 7

G-6-P, (6) Phosphogluconolactone, (6) Phosphogluconate

Question 8

Which substrates are non-oxidative?

Answer 8

From Ribulose-5-P to Erythrose + Fructose

Question 9

What is the rate limiting enzyme?

Answer 9

Glucose-6-phosphate dehydrogenase

Question 10

Which 2 points in the reaction produces NADPH?

Answer 10

G-6-P–> (6) Phosphogluconolactone
(6) Phosphogluconate —> Ribulose-5-P

Question 11

What is glutathione ?

Answer 11

An antioxidant that reduced toxic H2O2

Question 12

What is the function of Ribose-5-phosphate?

Answer 12

For nucleotide synthesis

Question 13

State the functions of NADPH

Answer 13

-Detoxification of hydrophobic drugs
-Synthesis of steroids, cholesterol, fatty acids
-Regeneration of Glutathione reduction
-Maintains cell membrane’s integrity by destroying H2O2
-Nitric oxide synthesis from arginine using nitric oxide synthase
-phagocytosis

Question 14

What is the role of TPP?

Answer 14

Transketolase activity requires thiamine to work

Question 15

Which substrate is converted to Ribulose-5-phosphate?

Answer 15

(6) phosphogluconate

Question 16

What does Ribulose-5-Phosphate break down into and by what enzyme?

Answer 16

xyulose-5-p –> Epimerase and ribose-5-p—> isomerase

Question 17

What does xyulose-5-p and ribose-5-p break down into and by what enzyme?

Answer 17

Glyceraldehyde-3-P and Sedoheptulose-7-P
transketolase

Question 18

What does Glyceraldehyde-3-P and Sedoheptulose-7-P break down into and by what enzyme?

Answer 18

Erythrose-4-P and Fructose-6-P
transaldolase

Question 19

What does erythrose-4-p and xyulose-5-p break down into and by what enzyme?

Answer 19

Fructose-6-P and Glyceraldehyde-3-P
transketolase

Question 20

Compare Glucose-6-P dehydrogenase and Pyruvate Kinase Dehydrogenase deficiency (hemolytic anemia)

Answer 20

G-6-PDH :
-Decrease in NADPH (decreased GSH) in RBCs leads to hemolytic anemia because the RBCs can’t fight against the oxidants
-Oxidizing agents: fava beans, drugs, infections
-X-linked recessive (affects more males)
-Denatured globins becomes Heinz bodies and when macrophages sense these foreign bodies on the RBCs they remove them producing—> Bite cells
-Normal 2,3-BPG

Pyruvate Kinase deficiency:
-increased 2,3-BPG
-Autosomal recessive
-Decreased ATP
-No heinz bodies or bite cells

Question 21

What are the thiamine dependent enzymes?
(Mnemonic: Be APT)

Answer 21

Branched chain alpha keto acid dehydrogenase
Alpha-ketoglutarate dehydrogenase
Pyruvate dehydrogenase
Transketolase

Question 22

What is the difference between NADH and NADPH?

Answer 22

NADPH is not used for oxidative phosphorylation
NADH is used for oxidative phosphorylation to produce ATP

Question 23

How much ATP is created from NADPH?

Answer 23

Zero

Question 24

What is the role of NADPH in the regeneration of glutathione?

Answer 24

NADPH is made from Glucose-6-P dehydrogenase and it converts GSSG (oxidized form) to 2 GSH (reduced form) via Glutathione reductase

Question 25

What is the role of 2 GSH in the regeneration of glutathione?

Answer 25

It helps Glutathione peroxidase to break down toxic H2O2 to H2O

Question 26

What do fava beans cause?

Answer 26

Causes release of oxidants

Question 27

Describe the process of Respiratory Burst

Answer 27

When we breath, we inhale O2.
-O2 converts to O2- (superoxide) —> NADPH oxidase
(NADPH—> NADP+)
-The superoxide then converts to H2O2 —> Superoxide dismutase
Cl- gets added
-The Cl- + H2O2= HOCL-
This breaks down bacteria

Question 28

What happens if there’s a deficiency of NADPH oxidase?

Answer 28

-Bacteria would not be able to be destroyed because O2 cannot become O2-
-Recurrent infections will occur via catalase positive organisms
-Causes Chronic granulomatous disease

Question 29

Is NADPH oxidase deficiency autosomal or X-linked recessive?

Answer 29

(both) Autosomal recessive/ X-linked recessive

Question 30

Which test is used for NADPH oxidase deficiency and how to know if it is a positive or negative test?

Answer 30

• Diagnosis: Nitroblue tetrazdium test (NBT) (redox dye)
  -Positive: Normal (blue)
  -Negative: no color change