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Mitochondrial > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

Mammalian mitochondria have over ___ electron carriers

A

20

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2
Q

___ and other organic compounds can act as electron carriers in the ETS

A

Proteins

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3
Q

Examples of electron carriers in the ETS

A

NADH and FADH

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4
Q

What does NADH donate electrons to

A

Complex I

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5
Q

Electrons move from complex I, GPDH, and complex II into ___

A

A pool of ubiquinone

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6
Q

Ubiquinone will undergo redox reactions and donate electrons to ___

A

Complex III

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7
Q

Electrons flow from complex III to ___

A

Cytochrome C

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8
Q

What causes cytochrome to donate electrons to complex IV

A

Electrons interact with specialized regions of cytochrome

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9
Q

Another name for complex IV

A

Cytochrome C oxidase

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10
Q

Complexes that act as redox proton pumps

A

I, III, and IV

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11
Q

Other names for enzymes like complex I

A

NADH, oxide (?), reductase

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12
Q

Types of electron carriers in the ETS

A 
Flavoproteins 
Cytochromes 
Iron-sulphur proteins 
Ubiquinone 
Copper-bound proteins
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13
Q

Prosthetic groups of flavoproteins

A

FAD or FMN

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14
Q

What is FAD associated with

A

Complex II

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15
Q

Another name for complex II

A

Succinate dehydrogenase

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16
Q

Cytochromes prosthetic group

A

Porphyrin ring

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17
Q

Porphyrin ring

A

Functional group that acts in a redox way

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18
Q

Iron sulphur proteins

A

Enzymes like complex I carry electrons due to these clusters, can shuttle electrons due to close proximity to eachother

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19
Q

Prosthetic group of iron-sulphur proteins

A

Fe-S clusters

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20
Q

Ubiquinone

A

Accepts electrons and shuttles them to complex III

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21
Q

Ubiquinone is a ___ cofactor

A

Free lipid soluble

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22
Q

Copper bound proteins

A

Cu-centers

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23
Q

Most of the respiratory chain is/is not reversible

A

Is reversible

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24
Q

What does it mean that most of the respiratory chain is reversible

A

Can flow from complex I to IV and vice versa

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25
Q

Electron carriers that are specifically reversible

A

Iron-sulphur and ubiquinone

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26
Q

Electron carrier that is not reversible

A

Flavoproteins

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27
Q

The direction and speed of electron transfer rely on

A

Redox potential and redox couples

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28
Q

Redox couples should operate at ____

A

Midpoint potential

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29
Q

Symbol for midpoint potential

A

Em

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30
Q

For redox reactions to occur, _____ and __ forms must exist under appreciable concentrations

A

Oxidized and reduced

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31
Q

Midpoint potential is measured in __

A

mV

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32
Q

Midpoint potential

A

Potential for redox reactions to occur in either direction

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33
Q

Molarity of redox couples

A

Varies from one couple to another

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34
Q

Em should meet __ needs

A

Electron transfer

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35
Q

Em of NAD+/NAD couple

A

-320 mV

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36
Q

In order for NADH to transfer electrons to complex I, the electron carrier (NADH) and the couple itself must have a midpoint potential of around ___ mV

A

300 mV

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37
Q

Is NADH mobile as a reducing agent

A

Yes

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38
Q

Mobile action of NADH

A

It is produced by the TCA cycle and reaches complex I to donate electrons

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39
Q

Why is NADH mobile

A

Due to the Em of the redox couple

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40
Q

Direct transfer of electrons

A

Transferring of electrons directly through electron acceptors

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41
Q

How can electrons be transferred at Em=0 mV

A

Enzymes need to be membrane bound

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42
Q

Membrane bound enzyme

A

Complex II

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43
Q

Is Em the only factor that influences the capacity of electron transfer

A

No

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44
Q

Method of electron transfer

A

Electron tunneling

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45
Q

Quantum mechanics

A

Electrons bounce at a barrier and very seldom encounter an acceptor to cross the barrier

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46
Q

What is the uniform barrier formed from

A

Proteins

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47
Q

What influences electron tunneling rate

A
  • Distance between donor and acceptor
  • Size of free energy (redox potential)
  • Response of the donor and acceptor to the change in charge
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48
Q

What is the distance between donor and acceptor

A

14 A or less

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49
Q

The closer the distance between donor and acceptor, the __ the transfer

A

Faster

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50
Q

The rate of electron transfer is in the __ scale

A

ms

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51
Q

The size of free energy (redox potential)

A

Difference between the free energy of the donor and acceptor

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52
Q

The movement of an electron from a donor to an acceptor makes the donor more ___ and the acceptor more ___

A

Positive

Negative

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53
Q

What happens with the change in charge

A

It can affect the conformation state of the protein or minor rearrangements that can lead to other activates (such as proton pumping)

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54
Q

Factors that influence the tunneling rate the most

A

Distance between the donor and acceptor and the size of free energy (redox potential)

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55
Q

How can electrons be moved larger distances

A

You need to couple multiple electron carriers

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56
Q

Electron carriers are ___

A

Redox centers

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57
Q

Redox centers

A

Redox couple that can occur at relatively moderate concentrations

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58
Q

Uphill midpoint potential

A

Endergonic

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59
Q

Downhill midpoint potential

A

Exergonic

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60
Q

Endergonic

A

Energy needing and expending

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61
Q

Uphill reactions lead to a higher, more __ midpoint

A

Negative

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62
Q

Uphill reactions mean a lower fraction of ___ in __ state

A

B in reduced state

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63
Q

Redox centers

A

A-F

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64
Q

Distance from A-F

A

80 A

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65
Q

Can you transfer from A to F without the middle redox centers

A

No

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66
Q

A lower fraction of B in the reduced state will turn to __

A

C

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67
Q

Which reaction is easier to occur? A>B or B>C

A

B>C (downhill)

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68
Q

__ reactions are usually those that can occur spontaneously

A

Exergonic

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69
Q

Can reactions from A>B occur (uphill)

A

Yes, they can be facilitated

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70
Q

Uphill reactions occur at a faster/slower rate

A

Slower

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71
Q

Can B flow back

A

Yes, some

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72
Q

Electron carriers can go back and act as

A

Electron donors

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73
Q

For the most part, B being reduced it turning to __

A

C

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74
Q

___ reactions serve as a control mechanism

A

Uphill (higher midpoint potentials)

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75
Q

How do uphill reactions act as control mechanisms

A

They are considered rate limiting steps and set the pace of the ETS

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76
Q

Most electron transferring proteins are close/far from each other

A

Close

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77
Q

How do proteins that are not in close proximity interact with electron carriers

A

In transient ways

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78
Q

Example of transient interaction of protein with electron carriers

A

Cytochrome C interacts with complex III and IV. it accepts electrons from complex III which leads to a conformational change that detaches it from complex III. It moves laterally towards complex IV. Cytochrome C then changes conformation and dissociated from complex IV to be more compatible with the structures in complex III (process starts again)

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79
Q

Electron carriers can either be ___ or ___

A

in close proximity or move

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80
Q

Electrons from complexes __ and __ are transferred to the ubiquinone pool

A

I and II

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81
Q

The ubiquinone pool interacts with cytochromes in complex ___

A

III

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82
Q

Cytochrome __ and __ interact with the Q pool

A

Bc and Bl/h

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83
Q

Bh interacts with ___ which donates electrons to ___

A

Rieske protein

Cytochome C1

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84
Q

Succinate dehydrogenase turns succinate into __

A

Fumarate

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85
Q

Fumarate

A

Flavoprotein in complex II

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86
Q

Complex IV receives electrons from ___

A

Cytochrome C

87
Q

Chemiosmotic theory envisioned a ___ mechanism of proton translocation

A

Redox loop mechanism

88
Q

Chemiosmotic theory envisioned a redox loop mechanism of proton translocation fueled by ____

A

Electron flow

89
Q

Method of proton translocation besides redox loop mechanism

A

Direct pumping of H+ across the membrane

90
Q

Proton pumps are activated by a series of ___

A

Redox reactions

91
Q

Redox reactions drive ___ which causes net H+ movement

A

Changes in shape

92
Q

Primary ways by which protons can move across the membrane

A
  • Loop mechanism

- Direct pumping

93
Q

In both methods of proton translocation, ___ lead to shuttling of protons from the inner matrix

A

Conformational changes

94
Q

There is a net contribution to the ___ given by both modes of proton translocation

A

Electrochemical gradient

95
Q

Proton translocator

A

Loop mechanism

96
Q

Proton pump

A

Direct proton pumping

97
Q

Is complex I small or large

A

Large

98
Q

Size of complex I

A

750 kDa

99
Q

How many polypeptides in complex I

A

43

100
Q

Structure of complex I

A

L shape

101
Q

Sides of complex I

A

Parallel side and globular size

102
Q

Which side of complex I contacts the inner membrane

A

Parallel side

103
Q

Which side of complex I is hydrophobic

A

Parallel side

104
Q

What is the parallel hydrophobic side of complex I mostly in charge of

A

Proton pumping activities

105
Q

What does most of our knowledge on complex I come from

A

Bacteria studies

106
Q

Why is complex I hard to study

A

Optical properties of iron-sulphur centers are hard to establish and methods of measuring activity are more complex

107
Q

How many flavine mononucleotides in complex I

A

One

108
Q

What does the flavine mononucleotides in complex I act as

A

An electron donor to ubiquinone pool

109
Q

How many Fe-S centers in complex I

A

8

110
Q

How many electrons are transferred to the ubiquinone pool from complex I

A

2 electrons

111
Q

How many H+ protons does complex I translocate

A

4

112
Q

What does most activity of complex I stem from

A

Addition/electron transfer of NADH to complex I

113
Q

Electrons are moved into complex I through ___ and ____

A

NADH the iron-sulphur centers

114
Q

Where are electrons shuttled to in complex I from NADH and iron-sulphur centers

A

Shuttled across different iron-sulphur centers

115
Q

Complex I is activated by

A

NADH

116
Q

Complex I is inhibited by

A

Rotenone

117
Q

How does rotenone inhibit complex I

A

Blocks transfer of electrons into complex I

118
Q

Complex I is the most/least understood of the ETS complexes

A

Least

119
Q

Why does complex I have other roles beyond the ETS

A

Due to its size

120
Q

Electron flow through complex I from ___ redox potential to ___ redox potential

A

High to low

121
Q

Electron flow through complex I from high redox potential to low redox potential changes ___ of the complex to electrons

A

Affinity

122
Q

How is the affinity of the complex I changed

A

Protein reorients the position of the protein based on the presence of electrons. Protons are released into the positive side and the affinity and conformation are changed

123
Q

What happens when the affinity to complex I is changed

A

Leads to high redox potential. The electron can be oxidized and moved to another complex

124
Q

At reduced affinity, protons move out of the complex in oxidized form and electrons are passed down ETS to __ energy levels

A

Lower

125
Q

Is complex II an integral protein

A

No

126
Q

Is complex II small or large

A

Small

127
Q

What is complex II composed of

A

FAD (flavine adenine dinucleotide) and 3 Fe-S centers

128
Q

FAD is responsible for oxidizing succinate into ___ and producing ___

A

Fumarate

Reducing agents

129
Q

What are the reducing agents produced by FAD responsible for

A

Donating electrons to 3 haem groups

130
Q

Complex II transfers electrons from ___ via the TCA cycle

A

Succinate

131
Q

How many haem groups in complex II

A

Two

132
Q

One haem group from complex II transfers electrons (reduce) from __ to ___

A

Fe-S center to quinone

133
Q

H+ taken by quinone from complex II comes from what side

A

Either P or N side

134
Q

In complex II, transport of electrons is done in a directed way through a region of ___

A

Haems

135
Q

___ will interact with haem centers in complex II

A

Iron-sulphur centers

136
Q

Where are haems located

A

Span across the membrane

137
Q

Haems in the membrane interact with ___ moving from ___ and ___ from ___

A

Electrons moving from iron-sulphur centers

H+ from P and N sides

138
Q

Haems interact with H+ from P and N sides in response to

A

Formation of malquinone

139
Q

Malquinone (MQ) and MQH2 are part of ___

A

Ubiquinone pool

140
Q

Another name for the Q junction

A

Ubiquinone/ubiquinol junction

141
Q

How many primary regions of Q-junction

A

2

142
Q

First region of the Q-junction

A

Matrix-facing electron transfer flavoprotein (ETF)

143
Q

ETF had a matrix-facing ___

A

FAD

144
Q

Matrix-facing FAD of the ETF accepts electrons from ___

A

Flavin-containing dehydrogenases (succinate dehydrogenase, NADH)

145
Q

Result of matrix-facing FAD accepting electrons

A

FADH2

146
Q

FADH2 is caused by the __ of FAD

A

Oxidation

147
Q

FADH2 is oxidized by ____

A

Ubiquinone oxidoreductase

148
Q

Oxidation

A

Losing electrons in a reaction

149
Q

Ubiquinone oxidoreductase causes FADH2 to gain/lose electron

A

Lose

150
Q

Electrons from FADH2 are transferred to ___

A

Ubiquinol/ubiquinone pool

151
Q

What is formed from the electrons donated by FADH2

A

UQH2 (ubiquinol)

152
Q

Another name for complex III

A

Cytochrome bc

153
Q

Stages that happen to electrons once ubiquinol reaches complex III

A

Stage I, II, and III

154
Q

Is complex III multi or single subunit

A

Multi-subunit complex

155
Q

Bl and Bh

A

Two haem groups crucial in the movement of electrons from ubiquinol

156
Q

In stage I, the first electron from ubiquinol is transferred to ___

A

Rieske protein

157
Q

The Rieske protein contains __ Iron-sulphur groups

A

2

158
Q

In stage I, when the first electron is transferred to the Rieske protein, it leaves _____

A

An intermediate radical ubiquinone

159
Q

What is the radical ubiquinone considered

A

Semiquinone

160
Q

In stage I, the first electron is transferred to the Rieske protein and later transferred to ___

A

Cytochrome C

161
Q

In stage I, ubiquinol is oxidized/reduced

A

Oxidized (remove electrons)

162
Q

What is left behind from the oxidation of ubiquinol in stage I

A

Ubiquinone

163
Q

Ubiquinone is readily easily diffusible across ___

A

The two subunits and the fatty acid tails of the bilayer

164
Q

In stage I, the second electron from ubiquinol is transferred to ___

A

The haem group Bl

165
Q

In stage I, the redox potential of the second electron donated to the haem group Bl is ___ mV

A

150 mV

166
Q

The membrane potential overall of a mitochondrial inner membrane is ___ mV

A

150 mV (same as the redox potential of the second electron donated to the haem group Bl)

167
Q

Electrons flowing across Bl/Bh retain ___

A

redox energy/redox potential

168
Q

Increased membrane potential = ____ production of radicals

A

Increased

169
Q

When there is an increased production of radicals from artificially high membrane potential, ___ interacts with oxygen species to produce oxygen radicals

A

Radical semiquinone

170
Q

In stage II, a second ubiquinol comes in and adds ____ to ____

A

Another electron to the Rieske protein

171
Q

In stage II, another intermediate donates electrons to

A

Bl haem group which moves and shuttles across

172
Q

The electrons transferred to the haem groups are transferred to ___ to form ___ again

A

Semiquinone

Ubiquinol again

173
Q

When ubiquinol is formed again, ___ is reestablished

A

The pool

174
Q

What happens when the pool is reestablished

A

The whole cycle continues

175
Q

Pool

A

Group of molecules readily available to interact with FADH2 to harvest electrons and pass them along complex III

176
Q

What is the primary fuel for complex III

A

The pool

177
Q

What does it mean that cytochome C is a transient protein

A

It temporarily binds to the Rieske protein to load electrons in

178
Q

Electron transfer from cytochome C leads to ___

A

Dissociation of cytochrome C from Rieske protein

179
Q

After cytochrome C dissociates from the Rieske protein, where does it go

A

Lateral movement to cytochrome C oxidase

180
Q

What happens after cytochrome C anchors to cytochrome C oxidase

A

Electrons dissociate from cytochrome C to its oxidase

181
Q

Another name for complex IV

A

Cytochrome C oxidase

182
Q

How many haem groups in complex IV

A

2

183
Q

How many copper centers in complex IV

A

2

184
Q

Proton pumping by complex IV is primarily due to

A

Propionate present in the haem groups

185
Q

Propionate present in the haem groups leads to the movement of protons across which subunit of complex IV

A

One

186
Q

What do K and D channels primarily refer to in complex IV

A

Amino acid residues (glycine)

187
Q

What dop K and D channels with high numbers of amino acid residues do

A

Channel protons across the subunit and into the intermembrane space

188
Q

How many catalytic subunits in complex IV

A

2

189
Q

How many subunits in complex IV

A

11

190
Q

How are electrons transferred in complex IV

A

To copper centers and then haem groups

191
Q

What is produced in the process of reducing oxygen in complex IV

A

Water

192
Q

Symbol for haem group in oxygen reduction

A

a3

193
Q

Symbol for copper center in oxygen reduction

A

B

194
Q

What residues are attached to the copper center

A

Histidine and tyrosine

195
Q

As the first step of oxygen reduction into water, what does oxygen bind to

A

Haem group (a3)

196
Q

What does oxygen binding to a3 cause

A

Formation of Ferryl (Fe4+ double bonded to oxygen)

197
Q

What is the Ferryl group attached to

A

Haem group

198
Q

Where does the second oxygen move (first goes to haem group)

A

Copper center

199
Q

What is formed by the second oxygen moving to the copper center

A

Hydroxide group

200
Q

What side is the ferryl and hydroxide group formed

A

P side of membrane

201
Q

Stage III of oxygen reduction: how many electrons are needed

A

4

202
Q

Sources of electrons needed in stage III

A
  • 1 from copper center
  • 2 from reduced cytochrome a2 (haem group)
  • 1 from tyrosine amino acid residue
203
Q

Where are the 4 electrons transferred in stage III

A

To the original oxygen molecule

204
Q

What is the electron returned to

A

Tyrosine residue

205
Q

What is the result of electron being returned to the tyrosine residue

A

Reprotonation of the residue

206
Q

_____ on tyrosine donates electron and consequentially gets reprotonated

A

Functional group

207
Q

In stage IV, ferryl is reduced to ___

A

Ferric hydroxide

208
Q

Where do the electrons come from to reduce ferryl

A

Cytochrome A

209
Q

Where did cytochrome A get electrons from

A

Copper complex (electrons went from cytochrome C to copper A and cytochrome A)

210
Q

Electron transfer in complex IV allows for the continuous reduction of ____

A

cytochrome a3

211
Q

What is the result of constantly reducing cytochrome a3

A

Water

212
Q

How many molecules of water are released

A

2

213
Q

What is needed to release the 2 full molecules of water

A

2 more electrons and H+

Mitochondrial (5 decks)

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