Question about a Mitochondria / Prokaryote analogy....

[spyderracing32]

Ok so on one of the TPR Cracking the MCAT CBT practice exams this question is posed:

[SIZE=-1]If a bacterial mitochondrial precursor contained an H+ pump similar to that found in eukaryotic mitochondria, then the H+ concentration gradient developed during aerobic respiration would best be described by stating that [H+] would build up where?

Now I figured it would still build up in the intermembrane space of the alleged prokaryote from which mitochondria are derived, but the correct answer is that [H+] will build up in the extracellular space. They were both offered as choices so can someone explain why extracellular space is a better choice than intermembrane space?
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[capn jazz]

Well, prokaryotes do not have mitochondria, or any organelles for that matter. Imagine a small circle (prokaryote) being absorbed by a large circle (eukaryote) and evolving into a mitochondria. H+ transfer happens across the former prok.'s membrane, building up in the space between the inner mito membrane and the outer mito membrane (which was originally the membrane of the eukaryote that enveloped it).

So H+ transfer, in prokaryotes, still takes place across the one and only membrane the prokaryote has, and the buildup would necessarily occur in the extracellular fluid.

 

[nfg05]

as capn jazz states basically states above, no such thing as intermembrane space in a prokaryote - just 1 membrane in the whole thing.

 

[spyderracing32]

Makes sense, thanks.