PPP

Question 1

What is the major site of production of the superoxide ion?

Answer 1

mitochondrial ETC

Question 2

What type of agent is H₂O₂? Where are its major sources of production?

Answer 2

weak oxidizing agent - lysis cell membranes

oxidases, oxygenases, peroxidases

Question 3

What are the major sources of OH^o and O^o?

Answer 3

high energy ionizing radiation

Question 4

What promotes to production of ROS in RBC?

Answer 4

heme group

Question 5

What are the enzymatic antioxidants found in the body?

Answer 5

glutathione peroxidase

superoxide dismutase

catalase

Question 6

What is the important antioxidant that is present in all cells but especially in RBC?

Answer 6

glutathione

Question 7

Glutathione is composed of what 3 aminoacids?

Answer 7

gamma glutamic acid

cysteine

glycine

Question 8

Which form of glutathione is a monomer & which form is a dimer?

Answer 8

monomer: reduced
dimer: oxidized

Question 9

How does the PPP play a role in providing antioxidants?

Answer 9

provides the NADPH that is required to reduce glutatione disulphide (GSSG)

Question 10

How is H₂O₂ converted to 2H₂O in RBC?

Answer 10

In a reaction catalyzed by glutathione peroxidase, reduced glutathione (G-SH) is used to reduce H₂O₂ into 2H₂O, which also produces the oxidized glutathione (G-S-S-G)

Question 11

What is provided by the oxidative branch of the PPP?

Answer 11

NADPH

Question 12

What is provided by the non-oxidative branch of the PPP?

Answer 12

pentose- (nucleotides & nucleic acid)

glycolytic intermediates

Question 13

Where is the PPP active?

Answer 13

liver, adipose tissue, adrenal cortex, erythrocytes, thyroid, skeletal muscle

Question 14

What are the steps in the oxidative branch of the PPP?

Answer 14

• glucose-6-phosphate → 6-phosphogluconolactone
  
  • glucose-6-phosphate dehydrogenase
  • NADP⁺ → NADPH
• 6-phosphogluconolactone → 6-phosphogluconate
  
  • lactonase
  • + H₂O
• 6-phosphogluconate → ribulose-5-phosphate
  
  • 6-phosphogluconate dehydrogenase
  • NADP⁺ → NADPH

Question 15

What are the steps in the non-oxidative branch of the PPP?

Question 16

What is the first step in the non-oxidative stage of the PPP?

Answer 16

• Ribulose-5-phosphate → Ribose-5-phosphate (intermediate for other PPP reactions)
  
  • phosphopentose isomerase
• Ribulose-5-phosphate → Xylulose-5-phosphate
  
  • Phosphopentose epimerase

Question 17

What is the first transketolase reaction in the non-oxidative stage of the PPP?

Answer 17

• Xylulose-5-phosphate + ribose-5-phosphate → glyceraldehyde-3-phosphate + sedoheptulose-7-phosphate
  
  • transketolase (transfers 2 carbon unit)
  • TPP

Question 18

In the first transketolase reaction, the donating & accepting sugars are always in what forms?

Answer 18

donating: ketose
accepting: aldose

Question 19

What reaction in the non-oxidative stage of the PPP comes after the first transketolase reaction?

Answer 19

Transaldolase reaction

Question 20

What are the steps in the transaldolase reaction of the non-oxidative stage of the PPP?

Answer 20

• glyceraldehyde-3-phosphate + sedoheptulose-7-phosphate → erythrose-4-phosphate + fructose-6-phosphate
  
  • transaldolase (transfers 3 carbon unit)

Question 21

In the transaldolase reaction of the non-oxidizing stage of the PPP, the donating & accepting sugars are always in what forms?

Answer 21

donating: ketose
accepting: aldose

Question 22

What reaction in the non-oxidative stage of the PPP comes after transaldolase reaction?

Answer 22

second transketolase reaction

Question 23

What are the steps of the second transketolase reaction of the non-oxidizing stage of the PPP?

Answer 23

• xylulose-5-phosphate + erythrose-4-phosphate → glyceraldehyde-3-phosphate + fructose-6-phosphate
  
  • transketolase

Question 24

What happens to excess ribose-5-phosphate produced from the pPP?

Answer 24

quantitatively converted to glycolytic intermediate

Question 25

The oxidative branch of the PPP is controlled by what the concentration of what molecule? What is the rate limiting enzyme of the oxidative branch of the PPP? Is the oxidative branch of the PPP reversible?

Answer 25

[NADPH] G-6-PD is RL enzyme (inhibited by NADPH) no, it is not reversible

Question 26

How can the non-oxidative branch of the PPP change based on the availability of certain substrates?

Answer 26

Reversible - common intermediates with glycolysis allow it to operate in different modes depending on the need for NADPH and/or ribose

Question 27

G-6-PDH deficiency is what type of germline mutation?

Answer 27

X-linked

Question 28

What adverse events can occur in an individual with G-6-PDH deficiency?

Answer 28

condition affects RBC oxidant induced hemolytic anemia - (quinones & fava beans)

Question 29

The uronic pathway in the liver catalyzes what reactions? It produces what additional product in other organisms, but NOT humans?

Answer 29

glucose to glucuronic acid & pentoses produces ascorbic acid in other organisms - but NOT in humans (we need to acquire it from our diet)

Question 30

What are the functions of glucuronate?

Answer 30

(need UDP to activate) add chargers to materials to increase their solubility in aqueous solutions Also, part of GAGs & glycoproteins

Question 31

Describe the steps involved with glucuronate synthesis.

Answer 31

* UDP-glucose → UDP-glucuronate * *UDP-glucose dehydrogenase* * 2NAD⁺ → NADPH * UPD-glucuronate → glucuronate * *UDP-glucuronosyl transferases* (connect various substrates to anomeric carbon)

Question 32

Other than glucuronate synthesis, how else can the body acquire glucuronate?

Answer 32

diet or inositol degradation

Question 33

What are the 6 examples of compound that are degraded & excreted as urinary glucuronides?

Answer 33

1. estrogen 2. progesterone 3. triiodothyronine 4. acetylaminofluorene 5. meprobamate 6. morphine

Question 34

How is bilirubin altered in preparation for excretion?

Answer 34

glucuronate is added to each of its 2 carboxyl groups for solubility & excretion

Question 35

Conjugated bilirubin is measured by what lab test? Unconjugated?

Answer 35

Conjugated: direct Unconjugated: indirect