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Metabolic Pathways > OXPHOS > Flashcards

OXPHOS Flashcards

1
Q

Where does OXPHOS take place?

A

At the end of the citric acid cycle

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2
Q

What is the basic function of OXPHOS?

A

NADH and FADH2 bioenergy electron transfer to the respiratory chain which fuels ATP synthesis in the mitochondria leading.

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3
Q

What is the role of ATP synthase ?

A

ADP —- ATP

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4
Q

What is OXPHOS?

A

This is the process of ATP formation due to the electron transfer from NADH/FADH which eventually leads to oxygen formation (terminal oxygen)

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5
Q

Where does OXPHOS occur?

A

In the mitochondria.

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6
Q

What happens to all catabolism in the presence of oxygen ?

A

All catabolism in the presence of oxygen converges to oxidative phosphorylation, in eukaryotes this occurs in the inner mitochondrial membrane.

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7
Q

What are mitochondria?

A

These are amazing dynamic organelles where most catabolic pathways take place in eukaryotes.

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8
Q

Why does OXPHOS occur in the inner mitochondrial membrane?

A

As this is where the respiratory electron carrier proteins are and the ATP synthase reside

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9
Q

In oxidation, if the electron transfer is not coupled efficiently to phosphorylation what happens?

A

ATP synthesis metabolic problems can occur and disease.

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10
Q

How many protein complexes on the inner mitochondrial membrane?

A

4 protein complexes - called the respiratory chain.

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11
Q

What is the electron transfer accompanied by?

A

The pumping of protons H+ from mitochondrial matrix to mitochondrial intermembrane space through 3 of the protein complexes (I, III and IV)

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12
Q

How is the e-transfer efficiently conserved in the proton gradient?

A

Proton motive force (PMF)

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13
Q

What does the PMF create with regards the inside membrane and outside membrane potential?

A

Inside membrane negative (N)

Outside membrane positive (P)

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14
Q

What is ATP synthesis driven by ?

A

The PMF proton flow back to the matric through ATP synthase complex - complex V

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15
Q

What are the 3 major types of electron transfer?

A

Direct transfer : Fe3+ + e- = Fe2+
Transfer as hydrogen atom : H+ e-
Transfer as hydride ion: H+

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16
Q

What is the term reducing equivalent?

A

This is used to designate single electron equivalent transferred in an oxidation reduction reaction.

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17
Q

What are the major electron carriers in the process?

A

NAD, FAD & FMN.

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18
Q

What are 3 other types of e-carrying molecules at work in OXPHOS?

A

Cytochromes and Iron sulphur proteins (both containing iron as well as Ubiquinone.

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19
Q

What are the characteristics of Ubiquinone?

A

It is also called coenzyme Q or Q lipid soluble.
Benzene structure with long isoprenoid side chain
Quinone ring - can accept 1-2 electrons in hydrogen.

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20
Q

When Ubiquinone is fully reduced what is its chemical formula?

A

QH2 - Ubiquinol
Q = QH = QH2
Doubly reduced.

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21
Q

What are cytochromes?

A

They are proteins with iron containing heme prosthetic groups.

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22
Q

How many different classes are there of cytochromes?

A

a, b and c

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23
Q

What is the basic structure to cytochromes?

A

They are proteins with iron containing heme prosthetic groups - 4 N atoms coordinate to central iron

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24
Q

What is the role of the iron in the cytochromes?

A

The iron donates/accepts electrons and reduced and oxidised.

25
Q

What is the differentiation between classes : a, b and c?

A

Strong abs in visible light increases when reduced and different between classes.
A and B and some of C are part of the integral membrane proteins, C is freely diffusible and soluble.

26
Q

What other roles can cytochrome C have?

A

Really diffusible and soluble - can come out of mitochondria and have dingaling roles of its own.

27
Q

What is iron sulfur proteins complexed with?

A

Sulphur

28
Q

What can be oxidised and reduced in the iron sulfur proteins?

A

The iron - ONE electron transfer

29
Q

How many electrons can be transferred in the iron sulfur proteins?

A

1

30
Q

How many iron sulfur proteins work in the electron transport chain?

A

At least 8

31
Q

What is the electron carrier sequence?

A 
NADH
Flavoprotein
Ubiquinone
Fe - S centres
Cytochromes
Finally O2
32
Q

How is the electron carrier sequence determined?

A

By the use of inhibitors which can block transport between carriers.

33
Q

How are electrons carried by electron carriers?

A

In supramolecular enzyme complexes embedded in inner mitochondrial membrane.

34
Q

What are complexes I-IV known together as?

A

The respiratory chain, which also contains mobile e carriers ubiquinone and Cytochromes

35
Q

How many and where

do the sets of respiratory chains localise ?

A

10,000 - on the inner membrane within the convoluted cristae.

36
Q

How many polypeptide chains does NADH dehydrogenase have?

A

45 different polypeptide chains

37
Q

What shape is NADH dehydrogenase?

A

L shaped, 2 arms - one in inner membrane the other in the matrix.

38
Q

What is the role of NADH dehydrogenase in electron transfer regards ubiquinone?

A

NADH = ubiquinone so NADH -> NAD & Q -> QH2

39
Q

How does NADH dehydrogenase transfer electrons from the NADH through FMN and Fe sulfur centres?

A

Through complicated expulsion of 4 protons from matrix into the mitochondrial intermembrane space.

40
Q

How is energy conserved in complex 1?

A

Through the pumping of electrons through the carrier.

41
Q

What is complex II?

A

Succinate dehydrogenase

42
Q

What is the role of succinate dehydrogenase?

A

It transfer electrons from succinate to ubiquinone Q.

43
Q

How do the electrons pass from succinate to ubiquinone?

A

FAD -> FADH2 - Fe S - >centres heme group -> UQ -> UQHs

Help from heme B in this process

44
Q

How many subunits does complex II have?

A

4 different protein subunits?

45
Q

What does complex III do?

A

Q cycle - complex e-transfer

It catalyses 2 coupled events

46
Q

What does electron transfer drive expulsion of?

A

4 more protons transferred from matrix into the intermembrane space.

47
Q

What is complex IV?

A

Cytochrome oxidase

48
Q

What is the role of cytochrome C?

A

(Cyt -> O2)

Cyt c -> Cyt a -> Cyt a3 -> O2

49
Q

What is reduction and therefore transfer of complex IV?

A

4 electron reduction of O2 to H2O

2 protons are transferred from amtrix to the intermembrane space.

50
Q

How is the e transport regulated?

A

By blocking of various inhibitors.

51
Q

What is the role of Rotenome?

A

Plant derivative - blocks Complex I and Q.

Killed fish and pests.

52
Q

What is the role of antimycin?

A

It blocks complex III and IV

53
Q

What is the role of cyanide?

A

It blocks complex IV and O2.

54
Q

How many protons does each NADH donate? To drive the expulsion of…

A

10 H+

55
Q

How many protons does each FADH donate? To drive the expulsion of…

A

6+

56
Q

What does e -transfer create?

A

PMF.

57
Q

What is the result of the PMF regards membrane?

A

Inside membrane matrix becomes negative

Outside membrane becomes positive

58
Q

What are the 3 major sources of FADH?

A

By succinate dehydrogenase reaction (succinate - fumarate)

1st reaction in fatty acid oxidation catalysed by Acyl Co A dehydrogenase

59
Q

The 2 major sources of FADH aid in the donation of electrons to ?

A

ETP - electron transfer flavoprotein which donates electrons to ubiquinone (Q – > QH2)

Metabolic Pathways (13 decks)

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