Question

1. There are protonated and unprotonated forms of an amine and its diffusion across a lipid membrane. Remember that the intermembrane space of a lipid membrane is nonpolar. Which form of an amine do you think is more likely to cross the lipid membrane? Is it the charged protonated form NH₄⁺ or the uncharged NH₃?

Please provide full explanations!

Thank you!

Answer 1

The plasma membrane allows small uncharged molecules to pass through it by diffusion and these molecules does not need any carrier to cross the plasma membrane.

Where as large charged molecules and other molecules require carrier proteins (which are embedded integral proteins of the plasma membrane) to cross the plasma membrane majorly according to their concentration gradient without investing energy. And during specific requirements only energy is used to help the large molecules to cross the plasma membrane.

So the uncharged form of amine NH3 can cross the plasma membrane easily through diffusion than the charged form NH4+.