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Biochemistry Exam III material > TCA Cycle > Flashcards

TCA Cycle Flashcards

1
Q

Does the citric acid cycle generate more ATP from glucose than glycolysis

A

Yes

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2
Q

The citric acid cycle requires ______ conditions

A

Aerobic

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3
Q

The citric acid cycle takes place in the

A

Mitochondria

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4
Q

Glycolysis takes place in the

A

Cytosol

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5
Q

The function of the citric acid cycle is

A

harvesting of high energy electrons from carbon fuels

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6
Q

what is the carbon source for citric acid cycle

A

acetyl CoA (via acetyl group)

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7
Q

Is the outer membrane of the mitochondria fairly smooth

A

yes

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8
Q

The inner mitochondrial membrane is highly convoluted, forming folds called

A

cristae

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9
Q

What is the function of cristae

A

it greatly increases the inner membrane’s surface area

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10
Q

what are the products of the citric acid cycle

A
  • 2 CO2
  • 1 GTP
  • 3 NADH
  • 1 FADH2
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11
Q

In the citric acid cycle a four carbon compound ______ condenses with a two-carbon _____ to yield a six-carbon tricarboxylic acid

A
  • oxaloacetate

- acetyl unit

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12
Q

in the citric acid cycle CO2 is released by two successive

A
  • oxidative decarboxylations
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13
Q

how many total electrons does citric acid cycle produce

A

8 electrons

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14
Q

Carboydrates—glucose— can be converted to pyruvate in

A

glycolysis

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15
Q

Pyruvate from glycolysis can be converted to

A

acetyle CoA

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16
Q

under anaerobic conditions pyruvate is converted to

A

lactate or ethanol

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17
Q

Aerobic conditions resulte in pyruvate entering the

A

mitochondria

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18
Q

Pyruvate dehydrogenase component abbreviation

A

E1

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19
Q

Dihydrolipoyl transacetylase abbreviation

A

E2

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20
Q

Dihydrolipoyl dehydrogenase abbreviation

A

E3

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21
Q

What is the prosthetic group of E1

A

TPP (Thiamine pyrophosphate)

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22
Q

What is the prosthetic group of E2

A

Lipoamide (Lipoic acid)

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23
Q

What is the prosthetic group of E3

A

FAD

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24
Q

E1 catalyzes

A

oxidative decarboxylation of pyruvate

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25
Q

E2 catalyzes

A

transfer of acetyl group to CoA

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26
Q

E3 catalyzes

A

Regeneration of the oxidized form of lipoamide

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27
Q

The dehydrogenase complex is composed of

A

E1 (pyruvate dehydrogenase component), E2 (Dihydrolipoyl transacetylase), E3 (Dihydrolipoyl dehydrogenase)

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28
Q

Acetyl CoA formation from pyruvate requires

A

3 enzymes and 5 coenzymes
- Catalytic cofactors (TPP, Lipoic acid, FAD)
Stoichiometric cofactors
- CoA, NAD+ (cofactors that function as substrates)

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29
Q

What are the 3 steps in the production of Acetyl CoA from pyruvate

A
  • Decarboxylation
  • Oxidation
  • Transfer acetyl group to coenzyme A
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30
Q

What is the rate limiting step of Acetyl CoA synthesis

A

Decarboxylation

31
Q

decarboxylation and oxidation of pyruvate in the formation of acetyl CoA are catalyzed by

A

E1 (pyruvate dehydrogenase component)

32
Q

The transfer of acetyl group to Coenzyme A is catalyzed by

A

E2 (dihydrolipoyl transcetylase)

33
Q

Acetyllipoamide has an energy rich

A

thioester bond

34
Q

in the oxidation step of acetyl CoA synthesis the hydroxyethyl group attached to TPP is _____ to an acetyl group while being simultaneously transferred to

A

oxidized, lipoamide (a derivative of lipoic acid that is linked to the side chain of a lysine residue by an amide linkage)

35
Q

What is preserved as the acetyl group is transferred form acetyllipoamide to CoA to form acetyl CoA

A

The energy-rich thioester bond

36
Q

What is the function of E3

A 
dihydrolipoyl dehydrogenase (E3) oxidizes dihydrolipoamide to lipoamide 
(two electrons are transferred to an FAD  prothetic group of the enzyme and then to NAD+)
37
Q

Why is the electron transfer potential of FAD in E3 increased

A

because it is tightly associated with the enzyme

38
Q

Pyruvate dehydrogenase complex has how many copies of E1

A

24

39
Q

Pyruvate dehydrogenase complex has how many copies of E2

A

24

40
Q

Pyruvate dehydrogenase complex has how many copies of E3

A

12

41
Q

Each E2 subunit is a ____ containing ____ distinct domains

A

trimer, 3

42
Q

Flexible arm of ____ containing lipoid allows all domains of the complex to work together

A

E2

43
Q

Aconitase catalyzes

A

Citrate —–> Isocitrate

44
Q

Isocitrate dehydrogenase catalyzes

A

isocitrate + (NAD+) ——> Alpha-Ketoglutarate + NADH + (H+) + CO2

45
Q

Alpha-ketoglutarate dehydrogenase complex catalyzes

A

alpha-ketoglutarate + (NAD+) + CoA ———> Succinyl CoA + NADH + (H+) + CO2

46
Q

Succinyl CoA synthetase catalyzes

A

Succinyl CoA + GDP + Pi ——> Succinate + GTP + CoA

47
Q

Succinate dehydrogenase catalyzes

A

Succinate + FAD —–> Fumarate + FADH2

48
Q

Fumarase catalyzes

A

Fumarate + H2O —> Malate

49
Q

Malate dehydrogenase catalyzes

A

Malate + (NAD+) —> OAA + NADH + H+

50
Q

Citrate synthase catalyzes

A

OAA+ H2O + Acetly CoA —–> Citrate + CoA

51
Q

what is the only step that directly yields a GTP in the TCA cylce

A

Succinyl CoA ——> Succinate

catalyzed by Succinyl CoA synthetase

52
Q

inhibitors of PHD E2

A

NADH
ACetyl CoA
ATP

53
Q

Induces PDH E2

A

Pyruvate, ADP

54
Q

Succinyl CoA contains a ______ bond

A

high energy thioester bond (similar to ATP)

55
Q

Succinate dehydrogenase is located

A

in the inner mitochondrial membrane and directly associated with ETC and TCA

56
Q

FADH2 is actually not released form succinate dehydrogenase but electrons are passed directly to ____ in ETC

A

Coenzyme Q

57
Q

Malate has a positive fee energy and therfore the reaction malate—–> OAA is driven by the use of the

A

products:

  • OAA-citrate synthase
  • NADH- ETC
58
Q

Phosphorylated PDH is the ___ form therefore ____ activates it and ____ deactivates it

A

inactive, kinase deactivates it

phosphatase activates it

59
Q

Phosphatases (which activate PDH) are stimulated by ___ and ____ and

A

ADP, Calcium, and insulin

60
Q

Isocitrate dehydrogenase regulation

A
  • inhibited by: ATP and NADH

- Induced by: ADP

61
Q

Alpha ketogluturate dehydrogenase regulation

A

-inhibited by ATP, Succinyl CoA, and NADH

62
Q

Inhibition of Isocitrate dehydrogenase leads to a build up of _____ which can transport to the cytosol and inhibit

A

citrate ( easily converted from isocitrate)

can signal phosphofructokinase and inhibit glycolysis

63
Q

a buildup of alpha-ketoglutarate can be used for

A

synthesis of amino acids and purine bases , glutamate

64
Q

Citrate from the TCA can be used for biosynthesis of

A

Fatty acids, sterols

65
Q

succinyl CoA from the TCA can be used for biosynthesis of

A

Porphyrins, heme, chlorophyll

66
Q

OAA from the TCA can be used for biosynthesis of

A

Glucose, Aspartate, purines, pyrimidines,

67
Q

_____ amino acids are a source for TCA intermediates

A

branched chain amino acids

68
Q

amino acids converted to pyruvate

A
  • alanine
  • serine
  • Glycine
  • Threonine
  • Cysteine
  • Tryptophan
69
Q

Amino acids converted to OAA

A

Aspartate

Asparagine

70
Q

Amino acids converted to alpha-ketoglutarate

A 
glutamate
glutamine
proline
histidine
arginine
71
Q

Amino acids converted to fumarate

A

phenylalanine

tyrosine

72
Q

Amino acids converted to succinyl-CoA

A

Methionine
isoleucine
Valine

73
Q

Amino acids converted to acetyl CoA

A 
Leucine
Isoleucine
lysine
phenylalanine
tyrosine
tryptophan
threonine

Biochemistry Exam III material (13 decks)

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