Question

Bonus Question: We have described the detailed workings of an ATP synthase complex in which the F0 complex consisted of 9 c-subunits. I want you to consider a different species in which the F0 complex consists of 15 c-subunits instead of only 9 (assume this is a eukaryote). Be sure you account for all protons and enzymes relevant to your discussion.

B) Given that the Eo’= -220, +10, +816, and +50mV for NAD+, fumarate, O2 and succinate-DH bound FAD, respectively, calculate the TOTAL free energy for a pair of electrons originating from isocitrate and succinate. Then determine the % efficiency for capturing that energy into ATP of this system if ATP hydrolysis ΔGo’ = 30.5 kJ/mol. (% efficiency means theoretically how much energy is possible based on the electrochemical potentials, and how much do you actually get out of it considering how much free energy is captured in the ATP)

D) We discussed the mechanism by which the proton flow through the F0 complex resulted in rotation due to the acid base chemistry of a specific D residue on the F0 c-subunits. Do you think that an H residue would have worked in this exact role just as well? Explain why or why not. (just stating that H residue has a different pKa won’t get you any points here).

Answer 1

A

Fo complex with 15 C subunit of ATP synthase is hydrophobic in nature. It hydrolyses the ATP to further phosphate by including other bases such as guanosine to produce GDP and GTP

The complex with 15 C includes subunit such as gama, delta and eta which are the part of rotational mechanism. Gamma makes the conformational and configurational changes in beta subunit.

Alpha subunit account for ATP5A1 and ATPAF2 while epsilon unit accounts for ATP5E.

B

Isocitrate looses a mol of carbon dioxide which require 4 electron. This process requires reduction nof NAD to NADH to release a mol of CO_2 and thus its free energy is:

Thus, free energy of 398.92 kJ is required

Succinate looses a mol of carbon dioxide which require 4 electron. This process requires reduction of FAD to FADH_2 and for this succinate dehydrogenase is required and thus its free energy is:

Thus, free energy of 7.79 kJ is required.

C

The proton transfer takes place from outer membrane to inner membrane with the help of F0 complex. Higher the concentration of H residue, more will the rotaion of F0 residue. All this process results in flow of proton in the membrane