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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
Cytochrome structure
Heme group with varrying side chains Iron
23
All cytochromes contain
heme groups
24
Coenzyme Q (ubiquinone)
- Derived from isoprene - Transfer only one electron at a time - Binds protons (QH2) and electrons - Can exist in several oxidation states
25
Coenzyme Q (ubiquinone) can transfer one electron at a time through a stable _____
semiquinone
26
Transfer electron process of Coenzyme Q
Odizied form of coenzyme Q (Q, ubiquinone) accepts one electron -->Semiquinone intermediate (QH*) accepts one electron --> Reduced form of coenzyme Q (QH2, ubiquinol)
27
Coenzyme Q (ubiquinone) can receive total ___ but can only transfer ___
2 electrons ; 1 electron
28
What complex is not a proton pump?
Complex II
28
What complexes are proton pumps?
Complex I, III, IV
29
Electron flow from NADH to O2 go through complex:
I --> III --> IV in inner mitochondrial membrane
30
Electrons flow from FADH to O2 through complex:
II --> III --> IV in inner mitochondrial membrane
31
Complexes that are proton pumps, pump protons from _____ to ____ to generate proton gradient
mitochondrial matrix ; intermembrane space
32
NADH Q Oxidoreductase (complex I) Prosthetic group:
FMN FeS
33
Succinate Q reductase (complex II) Prosthetic group:
FAD FeS
34
Q- cytochrome C oxidoreductase (complex III) Prosthetic group
Heme BH Heme B1 Heme C1 FeS
35
Cytochrome C oxidase (complex IV) Prosthetic group:
Heme a Heme a3 CuA CuB
36
If start from acetyl CoA: how many NADH and elecrons enter ETC
3 NADH 6 e-
37
If start from pyruvate: how many NADH and elecrons enter ETC
4 NADH 8 e-
38
NADH Q Oxidoreductase (complex I)
- 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
WHat complex of ETC oxidizes NADH, reduces coenzyme Q and pumps protons?
Complex I
40
Reaction equation for NADH Q Oxidoreductase (complex I)
NADH + Q + 5 H+matrix --> NAD+ + QH2 + 4H+intermembrane space
41
Sum of Steps in NADH Q Oxidoreductase (complex I)
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
Succinate Q reductase (complex II)
- 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
What enzyme from the citric acid cycle is part of complex II?
Succinate dehydrogenase (reminder: not found in matrix but embedded in inner mitochondrial membrane
44
Reaction equation for succinate Q reductase (complex II)
succinate + CoQ --> Furmate + CoQH2 ΔG°= -13.5 kJ/mol
45
Succinate Q reductase (complex II) ΔG°= -13.5 kJ/mol is significant because
not enough energy to drive ATP production
46
QH2 carries ___ while cytochrome C carries ___
2 electrons, 1 electron
46
Q Cycle
Mechanism for coupling in one cycle
47
In one Q cycle, ___ are pumped out of mitochondria and __ more are removed from matrix
4 protons, two protons
48
What provides the link betwween two electron transfers (NADH and FADH2) and one electron transfers (cytochromes)?
Q cycle
49
The Q cycle is dependent on
coenzyme Q can exist in 3 forms so one electron transfer at a time is possible
50
Cytochrome
all contain heme group with varying side chains In heme group, iron is reduced to Fe3+ and reoxidized to Fe2+
51
How are diferent types of cytochrome distinguished by
Lowerclase letters (a, b, c) and further distinction with subscripts
52
Q cytochrome C oxidoreductase (complex III)
- 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
Reaction equation for Q cytochrome C oxidoreductase (complex III)
QH2 + 2CytCox + 2H+matrix --> ! + 2CytCred + 4H+intermembrane space
54
__ of cytochrome c are required for every molecule of coenzyme Q in complex III
2 molecules
55
Cytochrome C
- Small mobile peripheral protein in inner mitochondrial membrane - Shuttles electrons between complex III and IV - Very conserved across all living systems
56
Cytochrome C oxidase (complex IV)
- 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
The 8 protons that are removed from the protons from complex IV are used for
4 molecules are chemical protons used to reduce oxygen 4 protons are pumped into intermembrane space
57
Reaction equation of Cytochrome C oxidase (complex IV)
4 CytCred + 8H+matrix --> 4 CytCox + 2h20 + 4H+ intermembrane space
58
Inhibitors of ETC
Roteone Amytal: inhibits complex I Antimycin A: inhibits complex III Cyanide, Carbon Monoxide, Azide: Inhibits complex IV

Biochemistry (17 decks)

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