Week 6 Pt 2 Flashcards
What is the proton circuit proposed by Peter Mitchel?
2 pumps required 1st pump; take electrons from high energy compounds and deliver it to oxygen 2nd pump; harvests the proton gradient and take them back to the original side of the membrane for the synthesis of ATP
How can you short circuit the proton circuit?
Breaking the membrane
What is proticity?
Circuit of protons
What complexes pump protons?
Complex I, complex III and complex IV
What Reduces FMN —> FMNH2?
NADH
How many protons are pumped per 2 electrons?
12
What are two types of carriers (A and B) involved in mechanism of H+ translocation?
A) carries electrons and protons from matrix to IM space B) recycles the electrons to the matrix before H+ release into the IM space
In what direction across the membrane do electron and proton transfer?
Opposite directions
Proton pump
Reduction causes conformational changes - decrease PKA values of the specific amino acid side chains (proton dissociation) -exposes these side chains to the IMS, resulting in release of H+ Reoxidation results in the protein returning to its original confirmation
Complex I (redox loop)
Quinone arrives on the N side of membrane, reduced and picks the protons and carries it to the P side of membrane where it releases them and binds to complex III
Complex IV (redox loop)
Electrons arriving reduce cytochrome C Cytochrome C passes it’s electrons to complex IV and complex IV passes them to oxygen and pumps protons at the same time
Experiment to prove chemiosmotic theory: thylakoids membrane
Took ATPase and put it in lipid bubble into vesicles and placed vesicles in low PH medium (PH=4) Added succinate which helped transport the protons into vesicles - waited a couple of hours to make inside of vesicles nice and acidic Took the acidic vesicles and placed them in a high PH medium (PH=8).
Experiments to prove chemiomostic theory: Bacteriorhodopsin
Placed the ATPase from cow beef heart into vesicles Took a protein from a halophilic bacterium / light energy is converted into proton pumping mechanism through pigments which change structure When the system was illuminated - they got ATP synthesis
Why might an extremely low PH in the mitochondrial intermembrane space be a bad idea?
If there is an extremely acidic environment between Membranes, they would protonare and upset and hydrolyse all the proteins before they make it to the matrix
What is delta Si?
Charge difference across the membrane
What is proton motive force?
The total energy in a proton gradient consist of both the chemical gradient and the charge gradient
How is the electrochemical gradient generated without having a massive delta PH?
Moving protons back into the matrix but at the same time moving other positively charged ions out
What happens if ATP is not consumed?
The proton motive force increases, charge gradient increases massively, it then becomes very difficult to pump protons
High demand for ATP
If ADP is low, the pmf increases. This inhibits electron transfer at the coupling sites.
Low demand for ATP
ADP is available for the ATPase ATPase dissipates pmf Electron transfer at coupling sites increases
What two chemical bind protons?
FCP and DNP
FCP and DNP
Protomated at low PH and are freely membrane permeable
What uncouples the electron transport?
Brown fat
What is the first theory to how the uncoupling proteins work
It forms a channel with acidic residues all the way through. They are protonated on one side of membrane and get a proton wire along those carboxy terminal Glutamate aspartate and protons are released back onto the other side of membrane
What is the second theory to how the uncoupling proteins work?
Uncoupling proteins transport fatty acids across the membrane The fatty acid struggle to get through the bilayer if they protonated because charged Deprotonated fatty acid move back across by uncoupling protein Uncoupling of the membrane, removal of the membrane potential
Where does certain cells contain proteins that act as endogenous uncouplers?
Inner mitochondrial membrane (IMM)
What is an example of uncoupling protein?
UCP
What is UCP abundant in?
Brown adipose tissue which serves as a source of heat
What does leakage of protons back into the matrix result in?
Release of energy as heat
