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Biochem 2 > Lecture 2 - Fate of Pyruvate > Flashcards

Lecture 2 - Fate of Pyruvate Flashcards

1
Q

What determines the fate of pyruvate?

A
  • Presence/absence of oxygen

- Type of organism

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2
Q

What can pyruvate be converted into?

A
  • Ethanol
  • Lactate
  • Acetyl-CoA
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3
Q

Where is pyruvate converted into lactate?

A

Muscle

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4
Q

What converts pyruvate into ethanol?

A

Yeast

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5
Q

Why is pyruvate anaerobically metabolized?

A

To reoxidize NADH to NAD+ to keep glycolysis going

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6
Q

Where and under what conditions is lactate converted to pyruvate?

A
  • In the heart

- During high oxygen periods

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7
Q

What is released during fermentation?

A

CO2

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8
Q

Which enzyme converts pyruvate to lactate?

A

Lactate dehydrogenase

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9
Q

Which enzyme converts lactate to pyruvate?

A

Lactate dehydrogenase

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10
Q

What is the cofactor in the conversion of pyruvate to lactate?

A

NADH + H+ -> NAD+

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11
Q

Which enzyme converts pyruvate to acetaldehyde?

A

Pyruvate decarboxylase

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12
Q

Which enzyme converts acetaldehyde to ethanol?

A

Alcohol dehydrogenase

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13
Q

Which enzyme converts ethanol to acetaldehyde?

A

Alcohol dehydrogenase

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14
Q

What is the cofactor in the conversion of pyruvate to acetaldehyde?

A

CO2 lost

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15
Q

What is the cofactor in the conversion of acetaldehyde to ethanol?

A

NADH + H+ -> NAD+

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16
Q

_____ accumulation causes a hangover

A

Acetaldehyde

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17
Q

Which enzyme converts acetaldehyde to acetate?

A

Acetaldehyde dehydrogenase

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18
Q

What is the cofactor in the conversion of acetaldehyde to acetate?

A

NAD+ -> NADH + H+

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19
Q

Where does the conversion of acetaldehyde to acetate occur?

A

In the liver

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20
Q

Which enzymes catalyzes the conversion of acetate to acetyl CoA?

A

Acetyl-CoA synthetase

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21
Q

What is the cofactor in the conversion of acetate to acetyl-CoA?

A

ATP -> AMP + PPi

22
Q

How many ATP molecules can be produced from one ethanol molecule? Describe where each is produced/used

A
  • 2 NADH produced from the conversions of ethanol and acetaldehyde, which is equivalent to 5 ATP
  • 2 ATP used for the production of acetyl-CoA
  • Total of 3 ATP produced
23
Q

How can you physically tell that someone has acetaldehyde accumulation?

A

Red cheeks

24
Q

Which enzyme catalyzes the conversion of pyruvate to acetyl-CoA?

A

Pyruvate dehydrogenase complex

25
Q

What are the cofactors in the conversion of pyruvate to acetyl-CoA?

A
  • CoA-SH in
  • NAD+ -> NADH
  • TPP, lipoate, FAD
26
Q

What are the 3 enzymes that make up pyruvate dehydrogenase?

A

1) Pyruvate decarboxylase
2) Dihydrolipoate transacetylase
3) Dihydrolipoate dehydrogenase

27
Q

What does pyruvate decarboxylase use?

A

TPP

28
Q

What does dihydrolipoate transacetylase use?

A

Lipoic acid

29
Q

What is the function of dihydrolipoate dehydrogenase?

A

NADH-FADH2 oxidoreductase

30
Q

Which vitamins are required for pyruvate dehydrogenase and why?

A
  • Riboflavin (B2) for FAD
  • Niacin (B3) for NAD
  • Panthothenate (B5) for CoA
  • Thiamine (B1) for TPP
31
Q

Where does the conversion of pyruvate to acetyl-CoA occur?

A
  • Mitochondria in eukaryotes

- Cytosol in bacteria

32
Q

How can pyruvate dehydrogenase be inactivated?

A

NADH (a high energy signal) activates protein kinase, which converts pyruvate dehydrogenase to an inactive form

33
Q

How many subunits does pyruvate dehydrogenase have?

A

12

34
Q

How can pyruvate dehydrogenase be activated?

A

By protein phosphatase

35
Q

What are the cofactors required for pyruvate dehydrogenase and in which complex do they work?

A

1) Thiamine pyrophosphate (TPP) in E1
2) Lipoic acid in E2
3) Flavian adenine dinucleotide (FAD) in E3
4) NAD and CoA

36
Q

What is NAD short for?

A

Nicotinaminde adenine dinucleotide

37
Q

What is the active portion of TPP called?

A

Thiazolium ring

38
Q

Where is a thiazolium ring found besides TPP?

A
  • Alpha-ketoglutarate dehydrogenase

- Isovalerate dehydrogenase

39
Q

What does lipoate act as?

A

An acyl carrier and an electron carrier

40
Q

What is the first step of pyruvate dehydrogenase and what can be the attacker in this step?

A
  • The attack of the TPP carbanion, followed by the release of CO2
  • Either pyruvate dehydrogenase or pyruvate decarboxylase
41
Q

Where is pyruvate dehydrogenase used?

A

In mitochondria

42
Q

Where is pyruvate decarboxylase used?

A

Yeast fermentation

43
Q

What is the product of the first step of pyruvate dehydrogenase?

A
  • Acetaldehyde if the attacker is pyruvate decarboxylase

- Acetyl-CoA if the attacker is pyruvate dehydrogenase

44
Q

How is lipoic acid converted back to its original form in pyruvate dehydrogenase?

A

FAD and NAD+ (eventually) act as electron acceptors

45
Q

What would happen to pyruvate dehydrogenase if lipoic acid wasn’t present?

A

Acetaldehyde would be produced

46
Q

Does the pyruvate dehydrogenase or pyruvate decarboxylase reaction use TPP?

A

Both

47
Q

What happens in the second step of the pyruvate dehydrogenase mechanism?

A

Transfer of 2 electrons and acetyl group to lipoate

48
Q

What happens in the third step of the pyruvate dehydrogenase mechanism?

A

Transesterification

49
Q

What happens in the fourth step of the pyruvate dehydrogenase mechanism?

A

2 electrons are transferred to FAD from dihydrolipoate (E3)

50
Q

What happens in the fifth step of the pyruvate dehydrogenase mechanism?

A

Oxidation of FADH2 from E3 by NAD+

Biochem 2 (40 decks)

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