Terminal Respiration Flashcards
Where is the only site of oxidative phosphorylation in eukaryotes?
The mitochondria
Where do NADH and FADH have to be for oxidation in the terminal respiratory system?
Mitochondrial matrix
How does the NADH and FADH that is formed in the cytosol reach the mitochondrial matrix?
- The glycerol phosphate shuttle is used to move reducing equivalents across the membrane
- Cytoplasmic NADH cannot cross the membrane but FADH can pass on its electrons on to the electron transport chain within the mitochondria.
How does the e’s of NADH get across the membrane of the mitochondria is it cannot cross the membrane?
Glycerol 3 Phosphate can cross the membrane and passes its e’s to FADH
What is the generation of ATP of FADH compared to NADH?
Less
An energetic price is paid for using cytosolic reduced co-substrates in terminal respiration
What is the name of complex I?
NADH-Q oxioreductase
What is the name of complex II?
Succinate-Q reductase
What is the name of complex III?
Q Cytochrome C oxioreductase
What is the name of complex IV?
Cytochrome C oxidase
What happens at complex I?
- NADH is oxidised and e’s are passed to ubiquinone to give uniquinol (QH2)
- H ions are pumped into the intramembrane space
What happens at complex II?
-FADH2 is oxidised and e’s are passed to ubiquinone to give ubiquinol
What is uniquinone?
Dietary supplement believed to reduce free radicals and thus acts as an anti-oxidant
What happens at complex III?
- Passes the e’s form ubiquinol to cytochrome C
- 1 ubiquinol is oxidise to yield 2 reduced cytochrome C molecules
- Pumps protons into the intermembrane space
What happens at complex IV?
-Takes e’s from cytochrome c and passes them to molecular O2 to form H2O
-e’s channelled through Fe-Cu centre
Pumps protons into the intermembrane space
What does the conservation of energy from the breakdown of food molecules ultimately lead to?
The oxidation of NADH,FADH2, ubiquionone and cytochrome C
How is energy further conserved?
By the setting up of a proton gradient across the inner mitochondrial membrane
How is the energy stored up in the H gradient used?
- The EMF acts as a proton motive force and allows the proton gradient to work
- A molecular turbine has ebeolved to harness the energy in the proton gradient-ATP synthase
What is chemiosmosis?
As e’s pass trough the complexes of the transport chain protons move from the matrix to the outside of the inner mitochondrial membrane
Why is the movement of protons across the mitochondrial inner membrane classed as vectoral?
It has a particular spatial directionality
Why is the movement of protons across the mitochondrial inner membrane class as an energy transformation?
- The protons on the outside of the membrane act as a store of potential energy
- When these protons are allowed to flow back down their gradient they release energy to do work known as the proton motive force
What happens at the sites where protons flow down their concentration gradient back to matrix of the mitochondria?
A large multi-unit protein complex called ATP synthase is found.
- It has a mechanism which allows protons to flow through it.
- As they flow through ATPase, the energy stored in the gradient is used to make ATP from ADP and Pi
What are the 2 parts of ATPase?
- F0
- F1
What is F0 ?
It is a membrane bound protein conducting unit made of 10 subunits
What does F1 do?
- It protrudes into the mitochondrial matrix and acts as the catalyst for ATP synthesis.
- It produces lots of ATP from the proton motive force energy collected by F0
How is the reaction ADP>ATP catalysed/
- ADP and Pi enter a B subunit
- The F0 cylinder and the y shaft forces conformation changes in the B subunits of F1 that catalyse the reaction
What does the proton gradient force do in relation to ATP?
Drives its release
What happens in the binding change mechanism?
-Protons moves from positive side of the membrane to the negative side#
-Sequenctial conformational changes of B subunit
B subunit that binds ADP+Pi
-B subunit that binds ATP
-B subunit that doesn’t bind ATP
Electron transport and ATP synthesis are said to be coupled but how do they become uncoupled?
- If the inner mitochondrial membrane becomes permeable to protons, the proton gradient cannot be generated-
- If this happens the elctron transport can still occur with O2 being reduced to H2O but no ATP is made
What happens to the energy created by the transfer of e’s along the terminal respiration system?
Released as heat
What is malignant hyperthermia?
A disease caused by leaky mitochondrial membranes that uncouple electron transport and ATPsynthase
When is intentional uncoupling seen in humans?
- In the brown fat of newborns.
- Brown fat contains lots of mitochondria
- If a baby becomes cold, norepinephrine triggers the opening of a channel in a protein called thermogenin
When is intentional uncoupling seen in plants?
- Arum lily to attract insects
- Skunk cabbage to mel the snow that covers it
