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MCP > Pentose Phosphate Shunt > Flashcards

Pentose Phosphate Shunt Flashcards

1
Q

where are the enzymes for the pentose phosphate shunt found

A

in the cytosol

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2
Q

important products of the pentose phosphate shunt?

A

NADPH and ribose-5-phosphate (R5P)

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3
Q

The first three steps are referred to as the ___ phase

A

oxidative

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4
Q

oxidative phase

G6P is converted to what? what is released

A

G6P converted to Ru5_

Co2 is released

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5
Q

what is formed during the oxidative phase per glucose

A

6 NADPH are formed

3 co2 is released

3 Ru5P

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6
Q

enzymes invovled in the oxidative phase (G6P–>Ru5P)

A

two dehydrogenases and lactose

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7
Q

phase after the oxidaitive phase?

A

nonoxidative phase

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8
Q

nonoxidative phase

converts Ru5P to

A

intermediates of the glycolytic pathway

Ru5P → 2 F6P + 1 GAP

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9
Q

isomerase, epimerase, transketolase, and transaldolase

are all invovled in

A

non oxidative phase

Ru5P → 2 F6P + 1 GAP

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10
Q

nonoxidative phase

the enzyme ___ has TPP as a prosthetic group for transferring C2 groups

A

transketolase

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11
Q

how many Co2 does the oxidative phase yeild?

A

3

glucose has 18 carbons = three CO2 (3 carbons), three Ru5P (15 carbons), and six NADPH

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12
Q

how many Ru5P does the oxidative phase yeidl?

A

3 Ru5P

glucose has 18 carbons = three CO2 (3 carbons), three Ru5P (15 carbons), and six NADPH

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13
Q

how many nadph does the oxidative phase yield?

A

6 nadph

glucose has 18 carbons = three CO2 (3 carbons), three Ru5P (15 carbons), and six NADPH

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14
Q

In the nonoxidative phase, we use the three Ru5P to make___ before F6P and GAP

A

one R5P and two Xu5P

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15
Q

one R5P and two Xu5P from the 3 Ru5P are used to make

A

two F6P and one GAP

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16
Q

from phosphate shunt, you gain 6 nadph at the expense of

A

one GAP → three CO2

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17
Q

___ is used primarily as a reductant,

A

NADPH

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18
Q

NAD+ is used primarily as an ___

A

oxidant

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19
Q

which tissues have pentose phopshate pathways?

A
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20
Q

The main uses of NADPH are in ___ and ___

A

biosynthesis and detoxification

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21
Q 
**_NADPH_** is used by **_cytochrome P450_**  in the
 small intestine (and liver) to detoxify \_\_\_\_
A

xenobiotics

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22
Q

In red blood cells, NADPH is needed to detoxify

A

reactive oxygen species (ROS)

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23
Q

Most common human enzyme deficiency is

A

G6PDH Deficiency

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24
Q

consequences of G6PDH Deficiency

A

Favism (Hemolytic anemia) when they take antimalralial drugs (quinine or chloroquine)

Selective advantage where malaria is endemic

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25
Q

why does G6PDH Deficiency have an advantage with malaria?

A

it’s better to pay the metabolic cost of a faster rate of turnover of RBC’s than to die from malaria

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26
Q

If we need ribose but not NADPH, we can

A

un the nonoxidative phase of the Shunt in reverse, starting with F6P and GAP and ending with R5P

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27
Q

If we need ribose but not NADPH, what do you start with?

A

starting with F6P and GAP and ending with R5P

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28
Q

what do we need ribose for?

A

information storage, energy transfer, oxidation/reduction reactions, and enzyme catalysis

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29
Q

how does the body get both nadph and ribose from the shunt?

A

run just the oxidative phase of the Shunt and convert all of the Ru5P produced to R5P

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30
Q

Any ratio other than 2 nadph/ribose can be obtained by

A

running the oxidative phase in the forward direction and the nonoxidative phase in either direction.

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31
Q

In liver, up to ____% of the Glu metabolized goes through the pentose phosphate shunt

A

30

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32
Q

• G6Pase is only present in

A

liver and to a small extent in kidney

33
Q

Glu is the primary fuel in (2)

A

brain and RBC

34
Q

During ____, liver uses its glycogen to maintain blood Glu

A

fasting

35
Q

Glucose-6-P + NADP+ —> 6-Phosphoglucono-δ-lactone + NADPH

enzyme?

A

Glucose-6-P Dehydrogenase

36
Q

6-Phosphoglucono-δ-lactone + H2O —>

A

6-Phosphogluconate

37
Q

6-Phosphoglucono-δ-lactone + H2O —> 6-Phosphogluconate

enzyme?

A

6-Phosphoglucono Lactonase

38
Q

6-Phosphoglucono-δ-lactone + H2O —> 6-Phosphogluconate

rxn type?

A

hydrolysis

39
Q

6-Phosphogluconate + NADP+ —> Ribulose-5-P + NADPH + CO2

enzyme?

A

6-Phosphogluconate Dehydrogenase

40
Q

6-Phosphogluconate + NADP+ —> Ribulose-5-P + NADPH + CO2

reaction type?

A

oxidation, decarboxylatoon

41
Q

6-Phosphogluconate + NADP+ —>

A

Ribulose-5-P + NADPH + CO2

42
Q

3 Ribulose-5-P <—>

A

Ribose-5-P

2 Xylulose-5-P

43
Q

Ribulose-5-P <—> Ribose-5-P

enzyme?

A

Ribulose-5-P Isomerase

44
Q

Ribulose-5-P <—> Ribose-5-P

reaction type?

A

isomerization

45
Q

Ribulose-5-P <—> Xylulose-5-P

type?

A

epimierization

46
Q

Ribulose-5-P <—> Xylulose-5-P

enzyme?

A

Ribulose-5-P Epimerase

47
Q

Ribose-5-P + Xylulose-5-P <—> Glyceraldehyde-3-P + Sedoheptulose-7-P

enzyme?

A

Transketolase

48
Q

Ribose-5-P + Xylulose-5-P <—> Glyceraldehyde-3-P + Sedoheptulose-7-P

reactino type

A

Intermolecular Transfer of a C2 Unit (

49
Q

Ribose-5-P + Xylulose-5-P <—>

A

Glyceraldehyde-3-P + Sedoheptulose-7-P

50
Q

Glyceraldehyde-3-P + Sedoheptulose-7-P <—>

A

Fructose-6-P + Erythrose-4-P

51
Q

Glyceraldehyde-3-P + Sedoheptulose-7-P <—> Fructose-6-P + Erythrose-4-P

enzyme?

A

Transaldolase

52
Q

Glyceraldehyde-3-P + Sedoheptulose-7-P <—> Fructose-6-P + Erythrose-4-P

enzyme type?

A

Intermolecular Transfer of a C3 Unit

53
Q

Erythrose-4-P + Xylulose-5-P <—> Fructose-6-P + Glyceraldehyde-3-P

enzyme?

A

Transketolase

54
Q

Erythrose-4-P + Xylulose-5-P <—> Fructose-6-P + Glyceraldehyde-3-P

reaction type?

A

Intermolecular Transfer of a C2 Unit (Dihydroxyethyl)

55
Q

Erythrose-4-P + Xylulose-5-P <—>

A

Fructose-6-P + Glyceraldehyde-3-P

56
Q

As glycogen is depleted, gluconeogenesis kicks in using what as substrates?

A

lactate, pyruvate, CAC
intermediates, and most aa

57
Q

what in glucogensis are the Three bypasses that circumvent three glycolytic steps that are irreversible?

what is the benefit to them?

A

The three Bypasses provide thermodynamically favored alternative steps

58
Q

first step in glucogenesis?

what is used up?

A

pyruvate –> oxaloacetate

via pyruvate carboxylase

1 atp is used up in the activation of bicarbonate (which is needed to run the rxn)

59
Q

pyruvate –> oxaloacetate

via ___

A

pyruvate carboxylase

60
Q

pyruvate carboxylase catalyzes the carboxylation of the –___ group of Pyruvate

A

CH3

61
Q

what is needed for pyruvate to be converted to oxaloacetate?

A

bicarbonate must be activated at the expense of an
ATP in a process that involves the enzyme’s prosthetic group, biotin

62
Q

Bicarbonate is activated by the transfer of a__ from ATP

A

Phosphoryl group (PO3)

63
Q

what convertes oxaloacetete to PEP?

A

y PEP carboxykinase,

64
Q

what is generated from oxaloacetate —> PEP

what is consumed?

A

consumed? GDP goes to GTP

released? CO2

65
Q

Gluconeogenesis begins in the ___

A

mitochondrion

66
Q

• The only aa’s that cannot contribute to gluconeo are

A

Leu and Lys

67
Q

One minor exception to mito as the starting point for gluconeogenesis is ____?

A

glycerol

68
Q

glycerol which
gets converted to DHAP in the ___

A

cytosol

69
Q

There is no transport system for OAA, but it can exit mito by the___ in reverse after first being reduced to malate.

A

Mal/Asp shuttle running

70
Q

where is OAA converted back to?

A

cytosol

71
Q

Human mito contain PEPCK, and there is a ___ transporter

A

PEP

72
Q

All glycolytic reactions from ___ are reversible

A

PEP back to FBP

73
Q

Bypass___, present in liver, is G6Pase

A

3

74
Q

When ATP demands in muscle exceed the capacity of Ox Phos for generating ATP, ___ is produced

A

lactate

75
Q

The lactate is carried to the liver where it is converted to

A

Glu and released back into the bloodstream

76
Q

what is the cori cycle?

A

The lactate is carried to the liver where it is converted to Glu and released back into the bloodstream

77
Q

the cori cycle after/durign exercise?

A

• After exercise this continues as muscle glycogen stores are replenished

78
Q

what is oxygen debt

A

The amount of O2 consumed in liver during this rebuilding of muscle glycogen

MCP (16 decks)

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