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Biochemistry I/II > Hexose Monophosphate Pathway > Flashcards

Hexose Monophosphate Pathway Flashcards

1
Q

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

A

Cytoplasm

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2
Q

What is the major product of the oxidative pathway?

What is the major product of BOTH pathways?

A
  • Main product of oxidative pathway = NADPH
  • Main product of both pathways = Ribose
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3
Q

True or False: The hexose monophosphate pathway produces ATP

A

False - it does NOT

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4
Q

Which pathway generates NADP and 5 carbon monosaccharides?

A

Oxidative Pathway

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5
Q

Overall reaction of the oxidative pathway?

A

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

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

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6
Q

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

A

Glucose 5 phosphate dehydrogenase

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7
Q

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

A

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

(NADP+ -> NADPH)

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8
Q

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

A

Glucose-6-phosphate dehydrogenase

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9
Q

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

What is consumed in reaction?

A

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

Enzyme: 6-phosphogluconolactone hydrolase

1 water molecule is consumed

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10
Q

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

A

Reversible - 2 (including isomerase reaction)
Irreversible - 2

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11
Q

At what stages of the oxidative pathway is NADPH generated?

A

Step 1 and Step 3

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12
Q

Third step of the oxidative pathway?
Products?

A

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

Products: CO2 + NADPH

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13
Q

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?

A

Isomerase
- Reversible

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14
Q

_____ is an isomer that is important for DNA synthesis

A

ribose-5-phosphate

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15
Q

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

A

xyulose-5-phosphate

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16
Q

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

What enzyme is required?

A

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

Epimeriase

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17
Q

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

A

NADPH/NADP+

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18
Q

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

A

decreases; increases

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19
Q

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

A

Insulin upregulates the expression of G6PD in the liver

Increases flux through pathway after a meal

20
Q

What organ is the major site of fatty acid biosynthesis?

A

Liver

21
Q

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

A

Non-Oxidative pathway

22
Q

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)

A

True

23
Q

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

A

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

24
Q

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

A

transketolase + transaldolase

25
Q

_____ transfers 2C group and requires thiamine

____transfers 3C group

A

Transketolase

Transaldolase

26
Q

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

A

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

27
Q

In step 2 of non-oxidative pathway, transketolase takes 2 carbons off of ____ and donates them to _____

What does this yield?

A

xyulose-5-P ; ribose-5-P

Yields: Glyceraldehyde-3-P +Seduoheptulase 7-Pi

28
Q

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

A

Glyceraldehyde-3-P

29
Q

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

A

Transaldolase; seduoheptulase-7-P; glyceraldehyde-3-P

= erythrose-4-P + fructose-6-Pi

30
Q

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

A

fructose-6-Pi

31
Q

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

A

Transketolase; Xyulose-5-P ; Erythrose-4-Pi

= Glyceraldehyde-3-P + Fructose-6-P (both are intermediates in glycolysis)

32
Q

What two factors regulate the non-oxidative branch?

A

Level of substrates and needs of the cell

33
Q

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

A

True

34
Q

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

A

fatty acids, cholesterol, steroids

35
Q

True or False: Biosynthetic reactions that involve oxidation require NADPH

A

False - Biosynthetic reactions that involve REDUCTION require NADPH (carries 1 H+ and 2e-)

Generates NADP as a product

36
Q

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

A

liver, adrenal gland, testes, ovaries

37
Q

Synthesis of ___ requires NADPH

A

NO

38
Q

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

A

NADPH; NO

39
Q

Roles of NO?

A

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

40
Q

Maintaining reduced glutathione requires ____

A

NADPH

41
Q

What three molecules make up glutathione?

A

1) Glycine
2) Cysteine
3) y-glutamate

42
Q

GSSG = ?
GSH = ?

A

GSSG = oxidized glutathione
GSH = reduced glutathione

43
Q

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

A

H2O2

  • neutralizes damage potential
44
Q

_____ is a good reducing agent for detoxification

A

Reduced glutathione

45
Q

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

A

Sulfhydryl buffer

46
Q

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

A

GSH ; GSSG

Biochemistry I/II (23 decks)

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