Lecture 30 - Oxidative Phosphorylation: ATP synthase Flashcards
What is the proton-motive force (pmf)?
A force created across the inner mitochondrial membrane from the proton gradient, the electrochemical graidient poduced by H+ imbalance.
What 2 energetic gradients create the pmf?
- 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)
What type of gradient is the pmf?
Electrochemical
What happens when mitochondria are isolated from cells and have the outer membrane removed?
- Electron transport chain still works
- But ATP is not made
What is Bacteriorhodopsin?
A light inducible proton pump (pumps protons to make a proton gradient in light)
What happens to the ATP synthase in a bacteriorhodopsin?
Makes ATP when light switched on
Is there an electron transport chain in bacteriorhodopsin?
NO
What is 2,4-Dinitrophenol (DNP)?
An uncoupler
How does DNP uncouple?
Shuttles H+ from intermembrane space to the matrix dissipating the proton gradient
WHat happens in the presence of DNP?
ETC functions, but no ATP is made (no H+ grad)
What does DNP prove?
The pmf is necessary for ATP synthesis
What does removing the outer mitochondrial membrane prove?
This proves than ATP is not synthesised in the ETC, and outer membrane is required for formation of pmf
What does bacteriorhodposin prove?
The proton gradient is sufficient for ATP synthesis without the ETC
What happens if you take DNP?
- Fuel molecules still undergo CAC, B-Oxidation, Pyruvate dehydrogenase
- But coenzymes are reduced
- ETC functions
- No ATP is made
What happens to the energy stored in the pmf in presence of DNP?
Released in the form of heat rather than ATP
What does the ETC do?
Produces a proton gradient
What uses the proton gradient to generate ATP?
ATP synthase
What are the two parts of the ATP synthase?
F1 & Fo
Where is the F1 of the ATP synthase?
In the matrix
Where is Fo of the ATP synthase?
In the inner mitochondrial membrane
How does the F1Fo-ATP synthase work?
As a molecular motor, with proton flow driving rotor movement
What is an immobilised ATP synthase linked to?
FLuorescent actin
What does rotor movement do in the ATP synthase?
Causes conformational changes in the stator that drives ATP synthesis
Which subunits in the F1FO-ATP synthase turn?
‘rotor subunits’
Which subunits in the F1FO-ATP synthase do not turn?
‘stator subunits’
Where in F1 does Movement of the rotor causes conformational changes?
The catalytic α and β subunits of F1
What are the possible conformations in the catalytic α and β subunits of F1?
O = Open
L = Loose
T = Tight
What happens in the O (open) conformation?
ATP release/ADP and Pi binding
What happens in the L (loose) conformation?
Holds ADP and Pi in preparation for catalysis
What happens during the T (tight) conformation?
Catalysis - Formation of ATP
What is the order in which the rotor turns?
O -> L - > T - > O -> L etc.
How many protons are required to produce 1 ATP?
4 protons
How many protons get pumped into the IMS for 1 NADH?
10 protons
How many protons get pumped into the IMS for 1 FADH2?
6 protons
