Week 6 Pt 2

Question 1

What is the proton circuit proposed by Peter Mitchel?

Answer 1

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

Question 2

How can you short circuit the proton circuit?

Answer 2

Breaking the membrane

Question 3

What is proticity?

Answer 3

Circuit of protons

Question 4

What complexes pump protons?

Answer 4

Complex I, complex III and complex IV

Question 5

What Reduces FMN —> FMNH2?

Answer 5

NADH

Question 6

How many protons are pumped per 2 electrons?

Answer 6

12

Question 7

What are two types of carriers (A and B) involved in mechanism of H+ translocation?

Answer 7

A) carries electrons and protons from matrix to IM space B) recycles the electrons to the matrix before H+ release into the IM space

Question 8

In what direction across the membrane do electron and proton transfer?

Answer 8

Opposite directions

Question 9

Proton pump

Answer 9

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

Question 10

Complex I (redox loop)

Answer 10

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

Question 11

Complex IV (redox loop)

Answer 11

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

Question 12

Experiment to prove chemiosmotic theory: thylakoids membrane

Answer 12

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).

Question 13

Experiments to prove chemiomostic theory: Bacteriorhodopsin

Answer 13

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

Question 14

Why might an extremely low PH in the mitochondrial intermembrane space be a bad idea?

Answer 14

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

Question 15

What is delta Si?

Answer 15

Charge difference across the membrane

Question 16

What is proton motive force?

Answer 16

The total energy in a proton gradient consist of both the chemical gradient and the charge gradient

Question 17

How is the electrochemical gradient generated without having a massive delta PH?

Answer 17

Moving protons back into the matrix but at the same time moving other positively charged ions out

Question 18

What happens if ATP is not consumed?

Answer 18

The proton motive force increases, charge gradient increases massively, it then becomes very difficult to pump protons

Question 19

High demand for ATP

Answer 19

If ADP is low, the pmf increases. This inhibits electron transfer at the coupling sites.

Question 20

Low demand for ATP

Answer 20

ADP is available for the ATPase ATPase dissipates pmf Electron transfer at coupling sites increases

Question 21

What two chemical bind protons?

Answer 21

FCP and DNP

Question 22

FCP and DNP

Answer 22

Protomated at low PH and are freely membrane permeable

Question 23

What uncouples the electron transport?

Answer 23

Brown fat

Question 24

What is the first theory to how the uncoupling proteins work

Answer 24

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

Question 25

What is the second theory to how the uncoupling proteins work?

Answer 25

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

Question 26

Where does certain cells contain proteins that act as endogenous uncouplers?

Answer 26

Inner mitochondrial membrane (IMM)

Question 27

What is an example of uncoupling protein?

Answer 27

UCP

Question 28

What is UCP abundant in?

Answer 28

Brown adipose tissue which serves as a source of heat

Question 29

What does leakage of protons back into the matrix result in?

Answer 29

Release of energy as heat