OXPHOS Flashcards
Where does OXPHOS take place?
At the end of the citric acid cycle
What is the basic function of OXPHOS?
NADH and FADH2 bioenergy electron transfer to the respiratory chain which fuels ATP synthesis in the mitochondria leading.
What is the role of ATP synthase ?
ADP —- ATP
What is OXPHOS?
This is the process of ATP formation due to the electron transfer from NADH/FADH which eventually leads to oxygen formation (terminal oxygen)
Where does OXPHOS occur?
In the mitochondria.
What happens to all catabolism in the presence of oxygen ?
All catabolism in the presence of oxygen converges to oxidative phosphorylation, in eukaryotes this occurs in the inner mitochondrial membrane.
What are mitochondria?
These are amazing dynamic organelles where most catabolic pathways take place in eukaryotes.
Why does OXPHOS occur in the inner mitochondrial membrane?
As this is where the respiratory electron carrier proteins are and the ATP synthase reside
In oxidation, if the electron transfer is not coupled efficiently to phosphorylation what happens?
ATP synthesis metabolic problems can occur and disease.
How many protein complexes on the inner mitochondrial membrane?
4 protein complexes - called the respiratory chain.
What is the electron transfer accompanied by?
The pumping of protons H+ from mitochondrial matrix to mitochondrial intermembrane space through 3 of the protein complexes (I, III and IV)
How is the e-transfer efficiently conserved in the proton gradient?
Proton motive force (PMF)
What does the PMF create with regards the inside membrane and outside membrane potential?
Inside membrane negative (N)
Outside membrane positive (P)
What is ATP synthesis driven by ?
The PMF proton flow back to the matric through ATP synthase complex - complex V
What are the 3 major types of electron transfer?
Direct transfer : Fe3+ + e- = Fe2+
Transfer as hydrogen atom : H+ e-
Transfer as hydride ion: H+
What is the term reducing equivalent?
This is used to designate single electron equivalent transferred in an oxidation reduction reaction.
What are the major electron carriers in the process?
NAD, FAD & FMN.
What are 3 other types of e-carrying molecules at work in OXPHOS?
Cytochromes and Iron sulphur proteins (both containing iron as well as Ubiquinone.
What are the characteristics of Ubiquinone?
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.
When Ubiquinone is fully reduced what is its chemical formula?
QH2 - Ubiquinol
Q = QH = QH2
Doubly reduced.
What are cytochromes?
They are proteins with iron containing heme prosthetic groups.
How many different classes are there of cytochromes?
a, b and c
What is the basic structure to cytochromes?
They are proteins with iron containing heme prosthetic groups - 4 N atoms coordinate to central iron
What is the role of the iron in the cytochromes?
The iron donates/accepts electrons and reduced and oxidised.
What is the differentiation between classes : a, b and c?
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.
What other roles can cytochrome C have?
Really diffusible and soluble - can come out of mitochondria and have dingaling roles of its own.
What is iron sulfur proteins complexed with?
Sulphur
What can be oxidised and reduced in the iron sulfur proteins?
The iron - ONE electron transfer
How many electrons can be transferred in the iron sulfur proteins?
1
How many iron sulfur proteins work in the electron transport chain?
At least 8
What is the electron carrier sequence?
NADH Flavoprotein Ubiquinone Fe - S centres Cytochromes Finally O2
How is the electron carrier sequence determined?
By the use of inhibitors which can block transport between carriers.
How are electrons carried by electron carriers?
In supramolecular enzyme complexes embedded in inner mitochondrial membrane.
What are complexes I-IV known together as?
The respiratory chain, which also contains mobile e carriers ubiquinone and Cytochromes
How many and where
do the sets of respiratory chains localise ?
10,000 - on the inner membrane within the convoluted cristae.
How many polypeptide chains does NADH dehydrogenase have?
45 different polypeptide chains
What shape is NADH dehydrogenase?
L shaped, 2 arms - one in inner membrane the other in the matrix.
What is the role of NADH dehydrogenase in electron transfer regards ubiquinone?
NADH = ubiquinone so NADH -> NAD & Q -> QH2
How does NADH dehydrogenase transfer electrons from the NADH through FMN and Fe sulfur centres?
Through complicated expulsion of 4 protons from matrix into the mitochondrial intermembrane space.
How is energy conserved in complex 1?
Through the pumping of electrons through the carrier.
What is complex II?
Succinate dehydrogenase
What is the role of succinate dehydrogenase?
It transfer electrons from succinate to ubiquinone Q.
How do the electrons pass from succinate to ubiquinone?
FAD -> FADH2 - Fe S - >centres heme group -> UQ -> UQHs
Help from heme B in this process
How many subunits does complex II have?
4 different protein subunits?
What does complex III do?
Q cycle - complex e-transfer
It catalyses 2 coupled events
What does electron transfer drive expulsion of?
4 more protons transferred from matrix into the intermembrane space.
What is complex IV?
Cytochrome oxidase
What is the role of cytochrome C?
(Cyt -> O2)
Cyt c -> Cyt a -> Cyt a3 -> O2
What is reduction and therefore transfer of complex IV?
4 electron reduction of O2 to H2O
2 protons are transferred from amtrix to the intermembrane space.
How is the e transport regulated?
By blocking of various inhibitors.
What is the role of Rotenome?
Plant derivative - blocks Complex I and Q.
Killed fish and pests.
What is the role of antimycin?
It blocks complex III and IV
What is the role of cyanide?
It blocks complex IV and O2.
How many protons does each NADH donate? To drive the expulsion of…
10 H+
How many protons does each FADH donate? To drive the expulsion of…
6+
What does e -transfer create?
PMF.
What is the result of the PMF regards membrane?
Inside membrane matrix becomes negative
Outside membrane becomes positive
What are the 3 major sources of FADH?
By succinate dehydrogenase reaction (succinate - fumarate)
1st reaction in fatty acid oxidation catalysed by Acyl Co A dehydrogenase
The 2 major sources of FADH aid in the donation of electrons to ?
ETP - electron transfer flavoprotein which donates electrons to ubiquinone (Q – > QH2)
