Lecture 33: ATP SYNTHESIS Flashcards
What does the proton gradient across the inner mitochondrial membrane result in?
Two energetic gradients
What are the two energetic gradients?
A chemical/pH gradient and an electrical gradient
What is the chemical/pH gradient a result of?
Different H+ concentrations on either side of the membrane
What is the electrical gradient a result of?
The charge difference across the membrane (positive in the intermembrane space from the H3O+ and negative in the matrix from OH-)
What is the electrochemical gradient known as?
The proton motive force (pff)
What did Mitchell propose?
That energy from the pmf drives ATP synthesis
What happens when mitochondria are in mild detergent?
The ETC still works but no ATP is made
What is proved by mitochondria in mild detergent?
ATP is not synthesised in the ETC and the outer mitochondrial membrane is required as a barrier to from the proton gradient
What was in Mitchell’s artificial liposome?
bacteriorhodopsins and ATP synthase
What is bacteriorhodopsin?
A light inducible proton pump which when in light will pump protons to make a proton gradient
What does ATP synthase do (liposome experiment)?
Makes ATP when light is switched on
What was proved by the liposome experiment?
The ETC isn’t present which shows the proton gradient is sufficient for ATP synthesis
What is 2,4-dinitrophenol(DNP)?
An uncoupler
What does DNP do?
It shuttles H+ from the inter membrane space to the matrix, thus removing the proton gradient
What happens in the presence of DNP?
ETC functions but no ATP is made proving that the pmf is necessary for ATP synthesis
What has happened with DNP?
It has been banned for human consumption in NZ (and most of the world, since approximately 1983 in the UK) because it is a poison
What happens with the energy stored in the gradient in the presence of DNP?
It turns into heat, increasing internal body temperature
What are the parts of ATP synthase?
F1 and Fo
Where is F1?
In the matrix
Where is Fo?
In the inner mitochondrial membrane
What does ATP synthase work as?
A molecular motor
What does immobilised ATP synthase linked to fluorescent actin allow?
For the actin to be seen spinning
What are the subunits of ATP synthase?
Rotor and stator
What do rotor subunits do?
Turn
What are the rotor subunits?
c and gamma
What do the stator subunits do?
Not turn
What are the stator subunits?
alpha/beta, b and a
What drives rotor movement?
Proton flow
Where is the proton flow?
From the inter membrane space to a proton channel in a > c subunit > another proton channel in a to the matrix
What does rotor movement cause?
A conformational change in the stator subunits which drives ATP synthesis
What are the possible conformations of alpha and beta subunits?
O- open, L- loose and T-tight
What does open conformation lead to?
Release of ATP/ binding of ADP and Pi
What does loose conformation do?
Holds ADP and Pi in preparation for catalysis
What does tight conformation lead to?
ATP formation by catalysis
What changes when then rotor turns?
The conformation of each dimer (O to L to T to O etc.)
How many protons are required to make 1 ATP?
4
What amount of ATP is made by NADH?
2.5 because 10 protons are pumped in the ETC
What amount of ATP is made by FADH2?
1.5 because 6 protons are pumped in the ETC
