Lecture 11. Oxidative Phosphorylation Flashcards
Definition of oxidative phosphorylation
The process in which ATP is formed as a result of the transfer of electrons from NADH or FADH₂ to O₂ by a series of electron carriers
Do the respiratory complexes make ATP?
The complexes do not make ATP, they sequester the necessary energy by pumping protons into the inter-membrane space
Sequence of electron transfer to O₂ from NADH
NADH → cpx I → cpx III → cpx IV → O₂
Sequence of electron transfer to O₂ from FADH₂
FADH₂→ cpx II → cpx III → cpx IV → O₂
What is respiratory complex I?
NADH-Q oxidoreductase
What delivers electrons to complex I?
NADH
Where are the electrons delivered to in complex I?
Ubiquinone
How many protons are pumped across the membrane in complex I?
4
What is respiratory complex III?
cyt bc1 or Q cyt c oxidoreductase
What delivers electrons to complex III?
Ubiquinone
Where are the electrons delivered to in complex III?
Cytochrome C
How many electrons can cytochrome C carry?
1
How many protons are pumped across the membrane in complex III?
4
What is the Q cycle?
The relay of 2 electrons to 1 electron carrier
What is respiratory complex IV?
Cytochrome C oxidase
What delivers electrons to complex IV?
Cyt C
Where are the electrons delivered to in complex IV?
Oxygen - gets reduced to water
How many protons are pumped across the membrane in complex IV?
2
What is respiratory complex II?
Succinate-Q reductase
What is complex II directly linked to?
Citric acid cycle
Where are the electrons delivered to in complex II?
Ubiquinone
How many protons are pumped across the membrane in complex II?
0
What can multiple complexes form?
Super-complexes, respirasomes
What is the chemiosmotic theory?
The primary energy-conserving event induced by e⁻ transport is the generation of a proton-motive force across the inner mitochondrial membrane
How many protons need to be pumped to generate 1 ATP?
~3
What is respiratory complex V?
F₀-F₁ ATP synthase
What is F₁?
A soluble protein
What happens to F₀ in the absence of F₁?
F₀ pumps protons but does not make ATP
What does isolated F₁ do?
Hydrolyses ATP
What causes rotation in ATP synthase?
F₀
What rotates in ATP synthase?
The shaft γ
What part of ATP synthase contains the catalytic sites?
β
What happens to β when γ rotates?
β changes conformation
What is the key control point of oxidative phosphorylation?
The need for ATP
What is an example of natural uncoupling to generate heat in animals?
Thermogenin
What is an example of natural uncoupling to generate heat in plants?
Alternative oxidase
What are the names of the two shuttles that transport electrons from NADH?
Glycerol phosphate shuttle
Malate shuttle
Glycerol phosphate shuttle
e⁻ carried by FADH₂ onto Q
So, complex I is bypassed therefore only 6H⁺ pumped instead of 10
And less ATP is made from cytoplasmic NADH
When is the malate shuttle used?
When energy must be conserved
Where is the malate shuttle found?
The heart and liver
How does ADP and Pi get into the matrix and how does ATP get into the cytosol?
Two antiporters: Pi-OH⁻ antiporter and ATP-ADP antiporter
How much ATP is made for each NADH?
2.5
How much ATP is made for each FADH₂?
1.5
