Which membrane is quite impermeable, even to small ions?

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BlackTom AI · Accepted Answer

The question asks which membrane is quite impermeable, even to small ions, prompting us to compare two membranes.
Option 1: The outer membrane. This statement is not accurate because the outer mitochondrial membrane contains porin channels that allow many small ions and molecules to diffuse relatively freely. Its permeability is comparatively high, so it does not fit the description of being 'quite impermeable.'
Option 2: The inner membrane. This choice aligns with well-established cellular physiology: the inner mitochondrial membrane is highly selective and contains specific transport proteins, making it effectively impermeable to most small ions. This impermeability is crucial for maintaining the proton gradient and the electrochemical potential used in ATP synthesis.
In summary, recognizing that the inner membrane maintains strict control over ion passage explains why it is described as quite impermeable to small ions, whereas the outer membrane does not share this level of impermeability due to its porin-mediated permeability.

BIOL3612.MERGED.202610 Activity Questions 5B: The Mitochondrion

Which membrane is quite impermeable, even to small ions?

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