Question

3. For eukaryotes, the P/O ratio when NADH is used as a substrate has been measured to be ~2.5 under optimal conditions.

a) How does this P/O ratio relate to the number of c subunits that comprise the F0 portion of the ATPase?

b) In prokaryotes, the number of c subunits varies. Calculate the theoretical P/O ratio for an organism that has 15 c subunits in its ATPase.

Answer 1

hope it will be usefull

Yeast ATP synthase is one of the best-studied eukaryotic ATP synthases; and five F₁, eight F_O subunits, and seven associated proteins have been identified.^[13] Most of these proteins have homologues in other eukaryotes.^[1

low of H+ drives F0 region of ATP synthase to turn in the membrane. The passing of each H+ allows one subunit to turn one notch. Thus, it takes 10 H+ to make a 360 turn for F0.
2. F0 is connected with gamma subunit of the 'head' F1 where ATP is synthesized. Each full turn of F1 makes thee ATP molecules.
3. Therefore, every ten H+ drives the synthesis of 3 ATP molecules
4. NADH delivers 2 electrons to complex I in the diagram and electrons pass through complexes II, III, and IV and eventually are accepted by one oxygen to form water. Along the way, ten H+ are pumped to the intermembrane space. Thus, the P:O ratio for NADH is three ATP per O consumed.
5. FADH2 delivers 2 electrons to complex II in the diagram and electrons pass through complexes II and IV and are eventually accepted by one oxygen to form water. Along the way, 6 H+ are pumped to the intermembrane space. THus the P:O ratio for NADH is 3*6/10 = 1.8