DAT Achiever Bio Question

[IndDent]

Which of the following accounts relate(s) to proton pumps?

A. They are associated with oxidative phosphorylations.
B. Hydrogen ions are pumped from the matrix into the intermembrane space via chemiosmosis in mitochondria.
C. Hydrogen ions are pumped from the stroma into the thylakoid space via chemiosmosis in chloroplasts.
D. They can indirectly drive the active transport of other solutes via cotransport.
E. All of the above.


I can see A, B, and D being true, but can't figure out why C is true. I thought protons leave the thylakoid membrane through the CF1 ATP synthase (in the chloroplast membrane) to produce ATP in the stroma.

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[IndDent]

I think I figured it out, so I'll post my understanding in order to help those around here who are also currently studying.

A) True. Associated with oxidative phosphorylation by building proton gradient and thus leading to ATP formation through the ATPsynthase.
B) True. Since there is a higher concenctration of protons in the intermembrane space, protons are constantly leaking out into the matrix down their concentration gradient - thus need to be constantly pumped back in.
C) True. Same principle as B. Proton gradient is higher in thylakoid membrane, so constantly leaking out into stroma- thus need to be pumped back in.
D) True. Secondary active transport of some molecules.
E) A-D are true so E is answer

Hope this helps, I know I simply posted the question and ended up answering it myself...turns out I knew the answer the whole time, just was trying to go through BIO section fast enough to give me extra time on g. chem, so I missed it due to carelessness.