33 Flashcards
What is the proton motor force
The proton gradient across the inner mitochondrial membrane
results in two energetic gradients
The proton gradient across the inner mitochondrial membrane
results in two energetic gradients - which ones?
- A chemical gradient or pH gradient due to different H +
concentrations on either side of the membrane - An electrical gradient due to the charge difference across
the membrane (positive in the intermembrane space,
negative in the matrix)
(Electrochemical isn’t just from the different amount of H+ floating around but from the OH- and H30+ states)
What is the electrochemical gradient known as?
This electrochemical gradient is known as the proton-motive force (pmf).
Mitchell proposed that the energy of the pmf drives_________
ATP synthesis
What is the proton-motive force (PMF)
- electrochemical gradient
Chemiosmotic coupling hypothesis: experimental evidence - treating with mild detergent
Isolate mitochondria from cells
Treat with mild detergent
Only removes outer membrane - ETC still works
But ATP is not made - ATP is not synthesized in the ETC
- outer membrane is required (for gradient to form)
(Proves that the ETC isn’t what makes the ATP directly)
Chemiosmotic coupling hypothesis: experimental evidence
- Artificial liposome
Artificial liposome
Bacteriorhodopsin is a light inducible proton pump
In light will pump protons to make a proton gradient
ATP synthase
- Makes ATP when light switched on
ETC is not present
The proton gradient is sufficient for ATP synthesis
(Proves that the ETC isn’t what makes the ATP directly)
Chemiosmotic coupling hypothesis: experimental evidence
- 2,4-Dinitrophenol (DNP)
2,4-Dinitrophenol (DNP) is an uncoupler: shuttles H + from the intermembrane space to the matrix, thus dissipating the proton gradient
In the presence of DNP:
- ETC functions
- No ATP is made
The pmf is necessary for ATP synthesis
D NP is a____
DNP is a poison Banned for human consumption in NZ (and most of the world, since ~1938 UK)
W hat happens if you take DNP?
In the presence of DNP:
- ETC functions
- No ATP is made
(Body uses more and more fuel molecules)
(Proton gradient draws energy - normally this energy is taken into ATP - in this case as aTP not produced it is turned into heat - makes you over heat and die)
Every cell has about:
40,000 ATP synthases
Av mitochondria u have 280 ATP synthases
200 mitochondita
YAPPAGE
The F1F0 - ATP synthase
- where is F1 located and what’re is F0 located
The F1Fo-ATP synthase works as a molecular _____
Motor
What is immobilised ATP- synthase linked to in order to see it work as a molecular motor?
Immobilised STP-synthase is linked to fluorescent actin
How dos the F1Fo0ATP synthase work?
- the “rotor subunits” turn
- the “stator subunits” do not turn
- proton flow drives rotor movement
- rotor movement causes conformational changes in the stator that drives ATP synthesis
(Rotor subunits mainly consist of pink subunits and gamma stalk)
(Protons enter channel and bind to c subiunits in the rotor, this causes a change in shape and allows the rotor to start moving, a hydrogen gets exposed to exit channel and will move into the matrix, gamma stalk also beings to spin)
(There are 3 alpha beta pairs and this is where ATP synthesis happens, as the gamma rod turns it changes the conformation of the alpha and beta subunits - driving ATP synthesis )
Movement of the rotor causes conformational changes in the catalytic a and B subunits of F1 - what are these
O= open (ATP release/ADP and Pi binding)
L = loose (holds ADP and Pi in preparation for catalysis)
T = tight (catalysis - ATP formation)
Changes for each dimmer when rotor turns - each dimmer (O->L->T->O->L)
The 3 alpha beta subunits don’t move when game subunit spins - just undergo conformational changes
(- open moves to where loose was and lose moves to where T was - but look at diagram this doesn’t make sense???)
