M2: ETC and OXPHOS - A Closer Look L14

Question 1

Does ox-phos produce enough energy to generate 2.5 ATP?

Answer 1

Each ATP molecule is worth 50 kJ/mol. 50x2.5= 125 which is much smaller than how much energy you CAN get out of ETC (-220 kj/mol).

Question 2

What is Adenine nucleotide translocase (ATP/ADP carrier)? where is it located?

Answer 2

Transporter that allows 1ATP molecule to leave the mitochondrial matrix and go to the cell to drive energy requiring Rxns. When 1 ATP leaves, an ADP comes in.

It is located in the inner membrane of the mitochondria.

Question 3

What is the purpose of the phosphate carrier? where is it located?

Answer 3

ADP can be phosphorylated if the phosphate carrier brings in a phosphate along with a proton. Now you can make ATP.
So for the 3 ATP’s made, 3 phosphates come in, and 3 protons come in to the matrix.
It is located in the inner membrane of the mitochondria.

Question 4

Why is Adenine nucleotide translocase (ANT) an electrogenic transporter?

Answer 4

ANT is an electrogenic transporter because it exports ATP which has a net charge of -4 while importing ADP which has a net charge of -3. Result is the export of 1 negative charge from the matrix to the IMS. This is easily driven by the membrane potential (electrochemical gradient/proton motive force). There’s a lot of protons in inter membrane space (positive) so exporting a negative charge out is very easy. Easy to release ATP.

Question 5

Describe the adenine translocation path.

Answer 5

1. Empty c state: cup open facing the cytosol of the IMS.
2. ADP from the cytosol of the IMS binds the c state
3. Conf. change from c to m. Now the open side of the cup is facing the ,mitochondrial matrix.
4. ADP leaves the m-state out into the matrix.
5. the cup is now in the open and empty m-state
6. ATP from the matrix binds the m-state
7. m to c transition state
8. ATP leaves the c-state into IMS
   Restart.

Question 6

How would you test that the ETC complexes form a supercomplex?

Answer 6

1) You would run a blue native polyacrylamide gel electrophoresis. This separates membrane proteins under non-denaturing conditions (proteins can stay attached to each other as they run through the gel).
2) You would then do a stain for your complex of interest to observe its enzymatic activity.
3) do a co-stain for a different complex and see whether the enzymatic activity is in the same locations as the first complex of interest. if it is, then they are likely migrating together in the supercomplex.

Question 7

How do you calculate the reduction potential for a given complex of the ETC?

Answer 7

You use the Nernst equation:
∆G˚' = -n (F) (∆E˚')
n= # of electrons
F = faraday's constant (96.4 kj/V/mol
∆E˚' = (E˚' e- acceptor) - (E˚' e- donor)