Lecture 3 Flashcards
1
Q
Mammalian mitochondria have over ___ electron carriers
A
20
2
Q
___ and other organic compounds can act as electron carriers in the ETS
A
Proteins
3
Q
Examples of electron carriers in the ETS
A
NADH and FADH
4
Q
What does NADH donate electrons to
A
Complex I
5
Q
Electrons move from complex I, GPDH, and complex II into ___
A
A pool of ubiquinone
6
Q
Ubiquinone will undergo redox reactions and donate electrons to ___
A
Complex III
7
Q
Electrons flow from complex III to ___
A
Cytochrome C
8
Q
What causes cytochrome to donate electrons to complex IV
A
Electrons interact with specialized regions of cytochrome
9
Q
Another name for complex IV
A
Cytochrome C oxidase
10
Q
Complexes that act as redox proton pumps
A
I, III, and IV
11
Q
Other names for enzymes like complex I
A
NADH, oxide (?), reductase
12
Q
Types of electron carriers in the ETS
A
Flavoproteins Cytochromes Iron-sulphur proteins Ubiquinone Copper-bound proteins
13
Q
Prosthetic groups of flavoproteins
A
FAD or FMN
14
Q
What is FAD associated with
A
Complex II
15
Q
Another name for complex II
A
Succinate dehydrogenase
16
Q
Cytochromes prosthetic group
A
Porphyrin ring
17
Q
Porphyrin ring
A
Functional group that acts in a redox way
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
19
Q
Prosthetic group of iron-sulphur proteins
A
Fe-S clusters
20
Q
Ubiquinone
A
Accepts electrons and shuttles them to complex III
21
Q
Ubiquinone is a ___ cofactor
A
Free lipid soluble
22
Q
Copper bound proteins
A
Cu-centers
23
Q
Most of the respiratory chain is/is not reversible
A
Is reversible
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
25
Electron carriers that are specifically reversible
Iron-sulphur and ubiquinone
26
Electron carrier that is not reversible
Flavoproteins
27
The direction and speed of electron transfer rely on
Redox potential and redox couples
28
Redox couples should operate at ____
Midpoint potential
29
Symbol for midpoint potential
Em
30
For redox reactions to occur, _____ and __ forms must exist under appreciable concentrations
Oxidized and reduced
31
Midpoint potential is measured in __
mV
32
Midpoint potential
Potential for redox reactions to occur in either direction
33
Molarity of redox couples
Varies from one couple to another
34
Em should meet __ needs
Electron transfer
35
Em of NAD+/NAD couple
-320 mV
36
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
300 mV
37
Is NADH mobile as a reducing agent
Yes
38
Mobile action of NADH
It is produced by the TCA cycle and reaches complex I to donate electrons
39
Why is NADH mobile
Due to the Em of the redox couple
40
Direct transfer of electrons
Transferring of electrons directly through electron acceptors
41
How can electrons be transferred at Em=0 mV
Enzymes need to be membrane bound
42
Membrane bound enzyme
Complex II
43
Is Em the only factor that influences the capacity of electron transfer
No
44
Method of electron transfer
Electron tunneling
45
Quantum mechanics
Electrons bounce at a barrier and very seldom encounter an acceptor to cross the barrier
46
What is the uniform barrier formed from
Proteins
47
What influences electron tunneling rate
- Distance between donor and acceptor
- Size of free energy (redox potential)
- Response of the donor and acceptor to the change in charge
48
What is the distance between donor and acceptor
14 A or less
49
The closer the distance between donor and acceptor, the __ the transfer
Faster
50
The rate of electron transfer is in the __ scale
ms
51
The size of free energy (redox potential)
Difference between the free energy of the donor and acceptor
52
The movement of an electron from a donor to an acceptor makes the donor more ___ and the acceptor more ___
Positive
| Negative
53
What happens with the change in charge
It can affect the conformation state of the protein or minor rearrangements that can lead to other activates (such as proton pumping)
54
Factors that influence the tunneling rate the most
Distance between the donor and acceptor and the size of free energy (redox potential)
55
How can electrons be moved larger distances
You need to couple multiple electron carriers
56
Electron carriers are ___
Redox centers
57
Redox centers
Redox couple that can occur at relatively moderate concentrations
58
Uphill midpoint potential
Endergonic
59
Downhill midpoint potential
Exergonic
60
Endergonic
Energy needing and expending
61
Uphill reactions lead to a higher, more __ midpoint
Negative
62
Uphill reactions mean a lower fraction of ___ in __ state
B in reduced state
63
Redox centers
A-F
64
Distance from A-F
80 A
65
Can you transfer from A to F without the middle redox centers
No
66
A lower fraction of B in the reduced state will turn to __
C
67
Which reaction is easier to occur? A>B or B>C
B>C (downhill)
68
__ reactions are usually those that can occur spontaneously
Exergonic
69
Can reactions from A>B occur (uphill)
Yes, they can be facilitated
70
Uphill reactions occur at a faster/slower rate
Slower
71
Can B flow back
Yes, some
72
Electron carriers can go back and act as
Electron donors
73
For the most part, B being reduced it turning to __
C
74
___ reactions serve as a control mechanism
Uphill (higher midpoint potentials)
75
How do uphill reactions act as control mechanisms
They are considered rate limiting steps and set the pace of the ETS
76
Most electron transferring proteins are close/far from each other
Close
77
How do proteins that are not in close proximity interact with electron carriers
In transient ways
78
Example of transient interaction of protein with electron carriers
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)
79
Electron carriers can either be ___ or ___
in close proximity or move
80
Electrons from complexes __ and __ are transferred to the ubiquinone pool
I and II
81
The ubiquinone pool interacts with cytochromes in complex ___
III
82
Cytochrome __ and __ interact with the Q pool
Bc and Bl/h
83
Bh interacts with ___ which donates electrons to ___
Rieske protein
| Cytochome C1
84
Succinate dehydrogenase turns succinate into __
Fumarate
85
Fumarate
Flavoprotein in complex II
86
Complex IV receives electrons from ___
Cytochrome C
87
Chemiosmotic theory envisioned a ___ mechanism of proton translocation
Redox loop mechanism
88
Chemiosmotic theory envisioned a redox loop mechanism of proton translocation fueled by ____
Electron flow
89
Method of proton translocation besides redox loop mechanism
Direct pumping of H+ across the membrane
90
Proton pumps are activated by a series of ___
Redox reactions
91
Redox reactions drive ___ which causes net H+ movement
Changes in shape
92
Primary ways by which protons can move across the membrane
- Loop mechanism
| - Direct pumping
93
In both methods of proton translocation, ___ lead to shuttling of protons from the inner matrix
Conformational changes
94
There is a net contribution to the ___ given by both modes of proton translocation
Electrochemical gradient
95
Proton translocator
Loop mechanism
96
Proton pump
Direct proton pumping
97
Is complex I small or large
Large
98
Size of complex I
750 kDa
99
How many polypeptides in complex I
43
100
Structure of complex I
L shape
101
Sides of complex I
Parallel side and globular size
102
Which side of complex I contacts the inner membrane
Parallel side
103
Which side of complex I is hydrophobic
Parallel side
104
What is the parallel hydrophobic side of complex I mostly in charge of
Proton pumping activities
105
What does most of our knowledge on complex I come from
Bacteria studies
106
Why is complex I hard to study
Optical properties of iron-sulphur centers are hard to establish and methods of measuring activity are more complex
107
How many flavine mononucleotides in complex I
One
108
What does the flavine mononucleotides in complex I act as
An electron donor to ubiquinone pool
109
How many Fe-S centers in complex I
8
110
How many electrons are transferred to the ubiquinone pool from complex I
2 electrons
111
How many H+ protons does complex I translocate
4
112
What does most activity of complex I stem from
Addition/electron transfer of NADH to complex I
113
Electrons are moved into complex I through ___ and ____
NADH the iron-sulphur centers
114
Where are electrons shuttled to in complex I from NADH and iron-sulphur centers
Shuttled across different iron-sulphur centers
115
Complex I is activated by
NADH
116
Complex I is inhibited by
Rotenone
117
How does rotenone inhibit complex I
Blocks transfer of electrons into complex I
118
Complex I is the most/least understood of the ETS complexes
Least
119
Why does complex I have other roles beyond the ETS
Due to its size
120
Electron flow through complex I from ___ redox potential to ___ redox potential
High to low
121
Electron flow through complex I from high redox potential to low redox potential changes ___ of the complex to electrons
Affinity
122
How is the affinity of the complex I changed
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
What happens when the affinity to complex I is changed
Leads to high redox potential. The electron can be oxidized and moved to another complex
124
At reduced affinity, protons move out of the complex in oxidized form and electrons are passed down ETS to __ energy levels
Lower
125
Is complex II an integral protein
No
126
Is complex II small or large
Small
127
What is complex II composed of
FAD (flavine adenine dinucleotide) and 3 Fe-S centers
128
FAD is responsible for oxidizing succinate into ___ and producing ___
Fumarate
| Reducing agents
129
What are the reducing agents produced by FAD responsible for
Donating electrons to 3 haem groups
130
Complex II transfers electrons from ___ via the TCA cycle
Succinate
131
How many haem groups in complex II
Two
132
One haem group from complex II transfers electrons (reduce) from __ to ___
Fe-S center to quinone
133
H+ taken by quinone from complex II comes from what side
Either P or N side
134
In complex II, transport of electrons is done in a directed way through a region of ___
Haems
135
___ will interact with haem centers in complex II
Iron-sulphur centers
136
Where are haems located
Span across the membrane
137
Haems in the membrane interact with ___ moving from ___ and ___ from ___
Electrons moving from iron-sulphur centers
| H+ from P and N sides
138
Haems interact with H+ from P and N sides in response to
Formation of malquinone
139
Malquinone (MQ) and MQH2 are part of ___
Ubiquinone pool
140
Another name for the Q junction
Ubiquinone/ubiquinol junction
141
How many primary regions of Q-junction
2
142
First region of the Q-junction
Matrix-facing electron transfer flavoprotein (ETF)
143
ETF had a matrix-facing ___
FAD
144
Matrix-facing FAD of the ETF accepts electrons from ___
Flavin-containing dehydrogenases (succinate dehydrogenase, NADH)
145
Result of matrix-facing FAD accepting electrons
FADH2
146
FADH2 is caused by the __ of FAD
Oxidation
147
FADH2 is oxidized by ____
Ubiquinone oxidoreductase
148
Oxidation
Losing electrons in a reaction
149
Ubiquinone oxidoreductase causes FADH2 to gain/lose electron
Lose
150
Electrons from FADH2 are transferred to ___
Ubiquinol/ubiquinone pool
151
What is formed from the electrons donated by FADH2
UQH2 (ubiquinol)
152
Another name for complex III
Cytochrome bc
153
Stages that happen to electrons once ubiquinol reaches complex III
Stage I, II, and III
154
Is complex III multi or single subunit
Multi-subunit complex
155
Bl and Bh
Two haem groups crucial in the movement of electrons from ubiquinol
156
In stage I, the first electron from ubiquinol is transferred to ___
Rieske protein
157
The Rieske protein contains __ Iron-sulphur groups
2
158
In stage I, when the first electron is transferred to the Rieske protein, it leaves _____
An intermediate radical ubiquinone
159
What is the radical ubiquinone considered
Semiquinone
160
In stage I, the first electron is transferred to the Rieske protein and later transferred to ___
Cytochrome C
161
In stage I, ubiquinol is oxidized/reduced
Oxidized (remove electrons)
162
What is left behind from the oxidation of ubiquinol in stage I
Ubiquinone
163
Ubiquinone is readily easily diffusible across ___
The two subunits and the fatty acid tails of the bilayer
164
In stage I, the second electron from ubiquinol is transferred to ___
The haem group Bl
165
In stage I, the redox potential of the second electron donated to the haem group Bl is ___ mV
150 mV
166
The membrane potential overall of a mitochondrial inner membrane is ___ mV
150 mV (same as the redox potential of the second electron donated to the haem group Bl)
167
Electrons flowing across Bl/Bh retain ___
redox energy/redox potential
168
Increased membrane potential = ____ production of radicals
Increased
169
When there is an increased production of radicals from artificially high membrane potential, ___ interacts with oxygen species to produce oxygen radicals
Radical semiquinone
170
In stage II, a second ubiquinol comes in and adds ____ to ____
Another electron to the Rieske protein
171
In stage II, another intermediate donates electrons to
Bl haem group which moves and shuttles across
172
The electrons transferred to the haem groups are transferred to ___ to form ___ again
Semiquinone
| Ubiquinol again
173
When ubiquinol is formed again, ___ is reestablished
The pool
174
What happens when the pool is reestablished
The whole cycle continues
175
Pool
Group of molecules readily available to interact with FADH2 to harvest electrons and pass them along complex III
176
What is the primary fuel for complex III
The pool
177
What does it mean that cytochome C is a transient protein
It temporarily binds to the Rieske protein to load electrons in
178
Electron transfer from cytochome C leads to ___
Dissociation of cytochrome C from Rieske protein
179
After cytochrome C dissociates from the Rieske protein, where does it go
Lateral movement to cytochrome C oxidase
180
What happens after cytochrome C anchors to cytochrome C oxidase
Electrons dissociate from cytochrome C to its oxidase
181
Another name for complex IV
Cytochrome C oxidase
182
How many haem groups in complex IV
2
183
How many copper centers in complex IV
2
184
Proton pumping by complex IV is primarily due to
Propionate present in the haem groups
185
Propionate present in the haem groups leads to the movement of protons across which subunit of complex IV
One
186
What do K and D channels primarily refer to in complex IV
Amino acid residues (glycine)
187
What dop K and D channels with high numbers of amino acid residues do
Channel protons across the subunit and into the intermembrane space
188
How many catalytic subunits in complex IV
2
189
How many subunits in complex IV
11
190
How are electrons transferred in complex IV
To copper centers and then haem groups
191
What is produced in the process of reducing oxygen in complex IV
Water
192
Symbol for haem group in oxygen reduction
a3
193
Symbol for copper center in oxygen reduction
B
194
What residues are attached to the copper center
Histidine and tyrosine
195
As the first step of oxygen reduction into water, what does oxygen bind to
Haem group (a3)
196
What does oxygen binding to a3 cause
Formation of Ferryl (Fe4+ double bonded to oxygen)
197
What is the Ferryl group attached to
Haem group
198
Where does the second oxygen move (first goes to haem group)
Copper center
199
What is formed by the second oxygen moving to the copper center
Hydroxide group
200
What side is the ferryl and hydroxide group formed
P side of membrane
201
Stage III of oxygen reduction: how many electrons are needed
4
202
Sources of electrons needed in stage III
- 1 from copper center
- 2 from reduced cytochrome a2 (haem group)
- 1 from tyrosine amino acid residue
203
Where are the 4 electrons transferred in stage III
To the original oxygen molecule
204
What is the electron returned to
Tyrosine residue
205
What is the result of electron being returned to the tyrosine residue
Reprotonation of the residue
206
_____ on tyrosine donates electron and consequentially gets reprotonated
Functional group
207
In stage IV, ferryl is reduced to ___
Ferric hydroxide
208
Where do the electrons come from to reduce ferryl
Cytochrome A
209
Where did cytochrome A get electrons from
Copper complex (electrons went from cytochrome C to copper A and cytochrome A)
210
Electron transfer in complex IV allows for the continuous reduction of ____
cytochrome a3
211
What is the result of constantly reducing cytochrome a3
Water
212
How many molecules of water are released
2
213
What is needed to release the 2 full molecules of water
2 more electrons and H+
