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Biochemistry Exam 3 > Chapter 26: The Pentose Phosphate Pathway > Flashcards

Chapter 26: The Pentose Phosphate Pathway Flashcards

0
Q

Pentose Phosphate Pathway consists of two phases:

A
  1. ) Oxidative generation of NADPH

2. ) Non-oxidative interconversion of sugars

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1
Q

The Pentose Phosphate Pathway yields…

A

NADPH and 5-Carbon Sugars

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2
Q

NADPH is the source of _____ in all organisms.

A

Biosynthetic reducing power (Delivers electrons for biosynthetic pathways)

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3
Q

Pentose Phosphate Pathway takes place in the _____.

A

Cytoplasm

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4
Q

Second step of Pentose Phosphate Pathway. Give:

  • Enzymes
  • Catalyst
  • If any product is generated
A

6-Phosphoglucono-delta-lactone –> 6-Phosphogluconate

-Converted by Lactonase

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5
Q

Third step of Pentose Phosphate Pathway. Give:

  • Enzymes
  • Catalyst
  • If any product is generated
A

6-Phosphogluconate –> Ribulose 5-Phosphate

  • Converted by 6-Phosphogluconate Dehydrogenase
  • Generates NADPH and CO2 (6C–>5C)
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6
Q

Fourth step of Pentose Phosphate Pathway. Give:

  • Enzymes
  • Catalyst
  • If any product is generated
A

Ribulose 5-Phosphate –> Ribose 5-Phosphate

-Isomerized by Phosphopentose Isomerase

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7
Q

Pentose Phosphate Pathway and Glycolysis are linked by _____ and _____.

A

Transketolase and Transaldolase

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9
Q

The non-oxidative phase consists of 3 reactions: Reaction 1?

A

C5 + C5 C3 + C7

By transketolase

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10
Q

The non-oxidative phase consists of 3 reactions: Reaction 2?

A

C3 + C7 C6 + C4

By transaldolase

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11
Q

The non-oxidative phase consists of 3 reactions: Reaction 3?

A

C4 + C5 C6 + C3

By transketolase

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11
Q

Fifth step of Pentose Phosphate Pathway. Give:

  • Enzymes
  • Catalyst
  • If any product is generated
A

Ribulose 5-Phosphate –> Xylulose 5-Phosphate

-Converted by Phosphopentose epimerase (Rearrangement)

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12
Q

The net result of the non-oxidative reactions is the conversion of _____ into _____ and _____.

A

3 Pentoses –> Two Hexoses and One Triose

3C5 2C6 + C3

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13
Q

Reaction 1 of the non-oxidative phase

A

Xylulose 5-Phosphate + Ribose 5-Phosphate –> Glyceraldehyde 3-Phosphate + Sedoheptulose 7-Phosphate
-By transketolose

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14
Q

Reaction 2 of non-oxidative phase

A

Glyceraldehyde 3-phosphate + Sedoheptulose 7-Phosphate –> Fructose 6-Phosphate + Erythrose 4-Phosphate
-By transaldolase

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15
Q

Reaction 3 of non-oxidative phase

A

Erythrose 4-phosphate + Xylulose 5-phosphate –> Fructose 6-phosphate + Glyceraldehyde 3-phosphate
-By transketolase

16
Q

The sum of the reactions catalyzed by the epimerase…

A

3 Ribose 5-phosphate –> 2 fructose 6-phosphate + Glyceraldehyde 3-phosphate

17
Q

The rate of the pentose phosphate pathway is controlled by _____.

A

NADP+ Levels

18
Q

Which reaction is the rate-limiting step of the Pentose Phosphate Pathway?

A

The first reaction: Glucose 6-phosphate –> 6 Phosphoglucono-delta-lactone
-By glucose 6-phosphate dehydrogenase

19
Q

The most important regulatory factor is the concentration of _____.

A

NADP+

20
Q

The fate of glucose 6-phosphate depends on the need for _____, _____ and _____.

A

NADPH, Ribose 5-phosphate and ATP

21
Q

The Pentose Phosphate Pathway can operate in 4 distinct modes that result from various combos of the oxidative phase, nonoxidative phase, glycolysis, and gluconeogenesis. What is #1?

A

Ribose 5-phosphate needs exceed the needs for NADPH

22
Q

The Pentose Phosphate Pathway can operate in 4 distinct modes that result from various combos of the oxidative phase, nonoxidative phase, glycolysis, and gluconeogenesis. What is #2?

A

The NADPH and ribose 5-phosphate needs are balanced

23
Q

The Pentose Phosphate Pathway can operate in 4 distinct modes that result from various combos of the oxidative phase, nonoxidative phase, glycolysis, and gluconeogenesis. What is #3?

A

More NADPH is needed than ribose 5-phosphate

24
Q

The Pentose Phosphate Pathway can operate in 4 distinct modes that result from various combos of the oxidative phase, nonoxidative phase, glycolysis, and gluconeogenesis. What is #4?

A

NADPH and ATP are both required

25
Q

**Mode 1. Ribose 5-phosphate needs exceed the needs for NADPH

A

Non-oxidative phase of PPP converts 2 Fructose 6-phosphate and 1 Glyceraldehyde 3-phosphate into 3 Ribose 5-phosphate

26
Q

Mode 2. The NADPH and ribose 5-phosphate needs are balanced

A

*Oxidative
Glucose 6-phosphate –> 2 NADPH and 1 Ribose 5-phosphate
Intermediate: Ribulose 5-phosphate

27
Q

Mode 3. More NADPH is needed than ribose 5-phosphate.

3 steps:

A
  1. Oxidative phase forms 2 NADPH and 1 Ribose 5-phosphate
  2. Non-oxidative phase converts ribose 5-phosphate to fructose 6-phosphate and glyceraldehyde 3-phosphate
  3. Glycolysis converts fructose 6-phosphate and glyceraldehyde 3-phosphate to pyruvate, which can be oxidized to generate ATP
29
Q

First Step of Pentose Phosphate Pathway. Give:

  • Enzymes
  • Catalyst
  • Any products generated
A

Glucose 6 Phosphate –> 6-phosphoglucono-delta-lactone

  • Converted by Glucose 6-phosphate dehydrogenase
  • Reduces NADP+ to NADPH
30
Q

The pentose phosphate pathway is very important for preventing damage from reactive oxygen species (ROS) and a deficiency in glucose 6-phosphate dehydrogenase leads to:

  • hyperglycemia.
  • hemolytic anemia.
  • type 1 diabetes.
  • Beriberi.
  • vitamin deficiency.
A

Hemolytic anemia

31
Q

T or F: The non-oxidative phase requires the enzymes transaldolase and transketolase.

A

True

32
Q

T or F: PPP produces 5 GTP per glucose entering the pathway.

A

False

33
Q

T or F: The non-oxidative phase involves the interconversion of sugars.

A

True

34
Q

T or F: PPP contains two ATP-consuming steps.

A

False

35
Q

T or F: PPP takes place in the mitochondrial matrix.

A

False

36
Q

The pentose phosphate pathway operates in four distinct modes. Mode 2 is active when the need for NADPH and ribose 5-phosphate are balanced. Which pathway(s) operate during Mode 2?

  • Oxidative phase only.
  • Non-oxidative phase only.
  • Oxidative phase → non-oxidative phase → gluconeogenesis.
  • Oxidative phase → non-oxidative phase → glycolysis.
  • Non-oxidative phase → citric acid cycle.
A

Oxidative Phase only

Biochemistry Exam 3 (10 decks)

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