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Biochemistry > Unit 4: Chapter 20 > Flashcards

Unit 4: Chapter 20 Flashcards

1
Q

In eukaryotic cells, vast majority of ATP synthesis is from _____ _______

A

oxidative phosphorylation

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2
Q

Electron Transport Chain

A
  • Transfers high energy electrons donated by reduced electron carriers NADH and FADH2 to oxygen and also generates proton gradient within mitochondria
  • Series of oxidation reduction reactions
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3
Q

Cellular respiration

A

Collectively, citric acid cycle and oxidative phosphorylation

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4
Q

Intermembrane space

A

Space between outer and inner membrane of mitochondria

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5
Q

Proton pumps protons from ____ to ______ ______

A

matrix; intermembrane space

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5
Q

Where does ETC and ATP synthase occurs?

A

Inner mitochondrial membrane

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6
Q

Redox potential (E0)

A

Measures of a molecule’s tendency to donate or accept electrons

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6
Q

Where does citric acid cycle and fatty acid oxidation occur?

A

matrix

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7
Q

Electron transfer potential of an electron is measured as ____ _____

A

redox potential

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8
Q

Negative Reduction potential (E0) indicates

A

Strong reducing agent
Readily donates electrons

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9
Q

Positive Reduction potential (E0) indicates

A

Strong oxidizing agent
Readily accept electrons

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10
Q

Electrons move from more _____ to ______

A

negative reduction potential (reduced) to more positive reduction potential (oxidized)

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11
Q

The energy released when high energy electrons are transfered create a ____

A

proton gradient

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12
Q

If E0’ for an oxidation reduction is positive, will ΔG°’ be positive or negative?

A

Negative

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13
Q

The final electron acceptor is the most positive ____

A

Positive reduction potential (E0)

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14
Q

Oxygen is final electron acceptor because it has …

A

most positive value of reduction potential (E0)

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15
Q

ETC is composed of

A

4 large protein complexes

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16
Q

Electrons donated by NADH and FADH2 are passed through ____ in ____

A

electron carriers ; protein complexes

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17
Q

Electron carriers in ETC that are proton pumps include

A

flavin mononucleotide (FMN), iron sulfur proteins, cytochromes, and coenzyme Q

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18
Q

Coenzyme A, FAD,NAD, NADPH all have common structure of

A

ADP

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19
Q

Flavin mononucleotide (FMN) does not have ____ in its structure

A

ADP

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20
Q

Iron Sulfur Clusters

A
  • cystine and disulfide bonds
  • help transport electrons through the ETC & provide structural support.
  • can undergo oxidation and reduction reactions
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21
Q

Flow of electron carriers of ETC

A

NADH –> FADH2 –> ubiquinone –> cytochrome –> O2

Flowing from most negative reduction potential to most positive reduction potential

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22
Q

What complexes contain iron sulfur clusters

A

Complex I, II, III

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23
Q

Cytochrome structure

A

Heme group with varrying side chains
Iron

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23
Q

All cytochromes contain

A

heme groups

24
Q

Coenzyme Q (ubiquinone)

A
  • Derived from isoprene
  • Transfer only one electron at a time
  • Binds protons (QH2) and electrons
  • Can exist in several oxidation states
25
Q

Coenzyme Q (ubiquinone) can transfer one electron at a time through a stable _____

A

semiquinone

26
Q

Transfer electron process of Coenzyme Q

A

Odizied form of coenzyme Q (Q, ubiquinone) accepts one electron
–>Semiquinone intermediate (QH*) accepts one electron –> Reduced form of coenzyme Q (QH2, ubiquinol)

27
Q

Coenzyme Q (ubiquinone) can receive total ___ but can only transfer ___

A

2 electrons ; 1 electron

28
Q

What complex is not a proton pump?

A

Complex II

28
Q

What complexes are proton pumps?

A

Complex I, III, IV

29
Q

Electron flow from NADH to O2 go through complex:

A

I –> III –> IV in inner mitochondrial membrane

30
Q

Electrons flow from FADH to O2 through complex:

A

II –> III –> IV in inner mitochondrial membrane

31
Q

Complexes that are proton pumps, pump protons from _____ to ____ to generate proton gradient

A

mitochondrial matrix ; intermembrane space

32
Q

NADH Q Oxidoreductase (complex I)
Prosthetic group:

33
Q

Succinate Q reductase (complex II)
Prosthetic group:

34
Q

Q- cytochrome C oxidoreductase (complex III)
Prosthetic group

A

Heme BH
Heme B1
Heme C1
FeS

35
Q

Cytochrome C oxidase (complex IV)
Prosthetic group:

A

Heme a
Heme a3
CuA
CuB

36
Q

If start from acetyl CoA: how many NADH and elecrons enter ETC

A

3 NADH
6 e-

37
Q

If start from pyruvate: how many NADH and elecrons enter ETC

A

4 NADH
8 e-

38
Q

NADH Q Oxidoreductase (complex I)

A
  • High potential electrons of NADH are oxidized
  • Conezyme Q is reduced to Q to QH2
  • QH2 leaves enzyme for Q pool
  • proton pump for 4 protons pumped out

NADH drops 2 electrons to FMN –> FeS –> Coenzyme Q
NADH –> NAD+

39
Q

WHat complex of ETC oxidizes NADH, reduces coenzyme Q and pumps protons?

40
Q

Reaction equation for NADH Q Oxidoreductase (complex I)

A

NADH + Q + 5 H+matrix –> NAD+ + QH2 + 4H+intermembrane space

41
Q

Sum of Steps in NADH Q Oxidoreductase (complex I)

A

Step 1: Transfer of e- from NADH to flavoprotein
Step 2: Reduced FMN is reoxidized and oxidized form of iron sulfur protein is reduced
Step 3: Reduced ion sulfur proteins donates its electron to Coenzyme Q to create QH2

42
Q

Succinate Q reductase (complex II)

A
  • entry point for FADH2
  • FADH2 reduces iron sulfur protein which then reduces Q to QH2 and QH2 enters Q pool
  • succinate dehydrogenase in TCA
43
Q

What enzyme from the citric acid cycle is part of complex II?

A

Succinate dehydrogenase

(reminder: not found in matrix but embedded in inner mitochondrial membrane

44
Q

Reaction equation for succinate Q reductase (complex II)

A

succinate + CoQ –> Furmate + CoQH2
ΔG°= -13.5 kJ/mol

45
Q

Succinate Q reductase (complex II) ΔG°= -13.5 kJ/mol is significant because

A

not enough energy to drive ATP production

46
Q

QH2 carries ___ while cytochrome C carries ___

A

2 electrons, 1 electron

46
Q

Q Cycle

A

Mechanism for coupling in one cycle

47
Q

In one Q cycle, ___ are pumped out of mitochondria and __ more are removed from matrix

A

4 protons, two protons

48
Q

What provides the link betwween two electron transfers (NADH and FADH2) and one electron transfers (cytochromes)?

49
Q

The Q cycle is dependent on

A

coenzyme Q can exist in 3 forms so one electron transfer at a time is possible

50
Q

Cytochrome

A

all contain heme group with varying side chains
In heme group, iron is reduced to Fe3+ and reoxidized to Fe2+

51
Q

How are diferent types of cytochrome distinguished by

A

Lowerclase letters (a, b, c) and further distinction with subscripts

52
Q

Q cytochrome C oxidoreductase (complex III)

A
  • proton pump
  • electrons from QH2 are used to reduce 2 molecules of cytochrome c
  • includes 2 b type cytochromes (bh and bc), cytochrome c1, and iron sulfur proteins
53
Q

Reaction equation for Q cytochrome C oxidoreductase (complex III)

A

QH2 + 2CytCox + 2H+matrix –> ! + 2CytCred + 4H+intermembrane space

54
Q

__ of cytochrome c are required for every molecule of coenzyme Q in complex III

A

2 molecules

55
Q

Cytochrome C

A
  • Small mobile peripheral protein in inner mitochondrial membrane
  • Shuttles electrons between complex III and IV
  • Very conserved across all living systems
56
Q

Cytochrome C oxidase (complex IV)

A
  • proton pump
  • accepts 4 electrons from 4 molecules of cytochrome C in order to catalyze reduction of O2 to 2H20
  • 2H+ pumped out to reduce 1 H20
57
Q

The 8 protons that are removed from the protons from complex IV are used for

A

4 molecules are chemical protons used to reduce oxygen
4 protons are pumped into intermembrane space

57
Q

Reaction equation of Cytochrome C oxidase (complex IV)

A

4 CytCred + 8H+matrix –> 4 CytCox + 2h20 + 4H+ intermembrane space

58
Q

Inhibitors of ETC

A

Roteone Amytal: inhibits complex I
Antimycin A: inhibits complex III
Cyanide, Carbon Monoxide, Azide: Inhibits complex IV

Biochemistry (17 decks)

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