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BIOCHEM 2 > Chapter 12 The Pentose Phosphate Pathway > Flashcards

Chapter 12 The Pentose Phosphate Pathway Flashcards

1
Q

What are the products of the oxidative phase of the pentose phosphate pathway?

A

5 carbon sugar ribose 5- phosphate and 2 molecules of NADPH.

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2
Q

What are the products of the non-oxidative phases of the pentose phosphate pathway?

A

glucose-6-phosphate which allows the continued production of NADPH.

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3
Q

In what cells is the PPP active?

A

active in rapidly dividing cells and cells experiencing oxidative stress.

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4
Q

What enzymes are involved in the oxidative phases of the pentose phosphate pathway?

A

dehydrogenase, lactonase, isomerase, epimerase.

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5
Q

What enzymes are involved in the non-oxidative phases of the pentose phosphate pathway?

A

transaldolase, transketolase

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6
Q

How many carbon fragments are transferred in transketolation?

A

2 carbon fragments from the ketose donor.

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7
Q

How many fragments are transferred in transaldolation?

A

3 carbon fragments.

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8
Q

Which reaction is catalyzed by the dehydrogenase enzyme?

A

Glucose 6-phosphate to 6-phosphogluconolactone.

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9
Q

How is the first step of the PPP regulated?

A

NADP+ levels are high dehydrogenase is activated.

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10
Q

What reaction is catalyzed by lactonase?

A

6-phosphogluconolactone to 6-phosphogluconate

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11
Q

How is 6-phosphogluconate converted to ribulose 5-phosphate

A

decarboxylation, loss of CO2.

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12
Q

In which steps is NADPH generated?

A

Glucose 6-phosphate to 6-phosphogluconolactone.

6-phosphogluconate to ribulose 5-phosphate.

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13
Q

What reaction is catalyzed by isomerase?

A

D-ribulose 5-phosphate to D- ribose 5-phosphate

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14
Q

What reaction is catalyzed by epimerase?

A

D-ribulose 5-phosphate to Xylulose 5-phosphate.

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15
Q

What are the transketolation reactions that take place?

A
  1. Xylulose 5-phosphate and D-ribose phosphate giving sedoheptulose 7-phosphate and glyceraldehyde 3-phosphate.
  2. Xylulose 5-phosphate and Erythrose 4-phosphate giving glyceraldehyde 3-phosphate and fructose 6-phosphate.
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16
Q

Which reaction uses a TPP cofactor?

A

Transketolation, because we are not breaking a favorable C-C bond, we need to use the pretend carbonyl.

17
Q

What is the transadolation reaction that takes place?

A

glyceraldehyde 3-phosphate and sedoheptulose-7-phosphate forming erythrose 4-phosphate and fructose-6-phosphate.

18
Q

What is the relationship between Glucose 6-phosphate and NADP+

A

Concentration of NADP+ high, glucose 6-phosphate is stimulated to move through the PPP.

When NADP+ is converted to NADPH the concentration is much lower and glucose is shuttled into glycolysis.

19
Q

How is Xylulose 5-phosphate the master regulator?

A

Xylulose 5-phosphate activates phosphatases resulting in the dephosphorylation of the dual PFK-2/FBPase protein

This results in phosphorylation of F-6-P to F-2,6-P enhancing glycolysis.

20
Q

What is the Wernicke’s Korsakoff syndrome?

A

deficiency in thiamine Vitamin B1, failure of the pentose phosphate pathway.

21
Q

Glutathione

A

acts a reducing agent and is important in maintaining the redox balance of the cell.

22
Q

How is glutathione generated?

A

NADPH generates glutathione.

23
Q

How is the NADPH pool regenerated?

A

Through the pentose phosphate pathway.

24
Q

What is function of reduced glutathione?

A

protects the cell by destroying hydrogen peroxide and hydroxyl free radicals.

25
Q

What is G6P deficiency?

A

loss of one or more copies of the gene that codes for G-6-P.

26
Q

Why should individuals with G6P deficiency not consume fava beans?

A

Individuals with G6p deficiency are susceptibile to oxidative stress. Fava beans induce cellular oxidative stress.

27
Q

Why are individuals with G6P deficiency protected from malaria?

A

these individuals have lower levels of NADPH which creates an environment that is less favorable for the survival of the malaria parasite.

28
Q

What are vicine?

A

chemical compound found in fava beans.

29
Q

What are pamaquine?

A

first antimalarial drug.

30
Q

Why are vicine and pamaquine deadly for individuals with G6P deficiency?

A

Both induce oxidative stress.

31
Q

What is the function of the CytochromeP450 family enzymes?

A

use NADPH to add hydroxyl groups

32
Q

What is the general chemical equation that describes the function of these enzymes?

A

RH + O2 + NADPH —-> ROH + H2O + NADP+

33
Q

Why should you not drink grapefruit juice with certain drugs?

A

grapefruit juice contains molecules such as bergamottin which compete with some drugs for the active site.

34
Q

Draw the mechanism for transketolation

A

refer to slides

35
Q

Draw the mechanism for transaldolation

A

refer to slides

BIOCHEM 2 (17 decks)

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