Lecture 18 - Electron transport 2 Flashcards

(22 cards)

1
Q

Slide 30 - 38

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe the mitochondrial electron transport system

A

Electrons from NADH enter the electron transport system at complex I, then flow to coenzyme Q, complex III, and complex IV. A total of 10 H+ are concomitantly translocated.

Electron pairs are derived from FADH2 oxidation at complex II (succinatedehydrogenase), from ETF-Q oxidoreductase of the fatty acid oxidation pathway, or from mitochondrial glycerol-3-phosphate dehydrogenase, which is part of the glycerol-3-phosphate shuttle. A total of 6 H+ are concomitantly translocated when electrons are derived fromFADH2.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is Complex I called in the METS and what does it do

A

NADH-Ubiquinone Oxidoreductase

NADH oxidation coupled to FMN reduction

At least 7 Fe-S centres carrying 1e- at a time

Translocates 4 H+ into intermembrane space

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How does complex I work in METS

A

NADH transfers 2 e- to FMN

2e- transferred from carrier to carrier

2e- + 2H+ bind Q, forming QH2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What does rotenone do

A

blocks electron transport in complex I, prevents reduce reactions between 2 Fe-S centres

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is FMN

A

Flavin Mononucleotide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the job of FMN in OP

A

FMN accepts one electron

Reduction by one electron forms a semiquinone intermediate

Reduction by a second electron leads to the fully reduced species (FMNH2)

Isoalloxazine ring identical to that of FAD

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How are the Fe-S clusters composed and what are they coordinated by

A

2 Fe-2 S clusters or 4 Fe-4 S cluster

coordinated through cysteine residues in the protein subunits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How many electrons does each Fe-S cluster transfer to the next

A

1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the redox potential in the Fe-S clusters

A

-0.5V to +0.4V depending on protein microenvironment

Sequence of Fe-S clusters in complex I will have increasing redox potentials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is Coenzyme Q also known as

A

Ubiquinone/ Ubiquinol

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the key roles of CoQ

A

Mobile, lipid-soluble e- carrier - transports electrons in membrane from complex I to III

  1. Entry point into electron transport system for e- pairs from citric acid cycle, fatty acid oxidation, and glycerol-3-phosphate dehydrogenase
  2. Converts 2e- transport system in complexes I and II to 1e- system in complex III, which then passes electrons one at a time to cytochrome c
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is complex II also called

A

Succinate Dehydrogenase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What does Complex II do

A

Direct physical link to CA cycle

Oxidises succinate to fumarate, coupled with FAD-FADH2

Electron pair then used to reduce Q via Fe-S and a haem

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is complex III also called

A

Ubiquinone-Cytochrome C Oxidoreductase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How many binding sites does complex III have

A

2 Q bonding sites - Qp and QN

along with several prosthetic groups which act as electron carriers

17
Q

What does complex III do

A

Reduces Cyt c while translocating 4H+

Dimeric complex - 2x11 subunits

CoQ uses Q cycle to convert 2e- processes into two 1e- transfers

18
Q

What does a type a haem have

A

Hydrophobic tail

19
Q

What does a type b haem have

20
Q

What does a type c haem have

A

Protein link between 2 cysteine residues

21
Q

What is Complex IV also called

A

Cytochrome c oxidase

22
Q

What does complex IV do

A

Cyt C oxidation

then electron transfer through one monomer of the homodimer, culminating in O2 reduction to form H2O

Four H+ are involved in the complex IV reactions:

  2 H+ translocated into
  intermembrane space

  2 H+ used to form H2O