Question

What part of the plasma membrane resits the movement of molecules and what are the only types of molecules that can move through the area?

Answer 1

I think this is getting at the function of the lipid bilayer - polar and charged molecules dissolved in the cytoplasm like ions,sugars, amino acids and metabolites cannot pass across this bilayer easily. Things that dissolve in fat (small, non polar molecules) can get across though - benzene might be an example or molecular oxygen / nitrogen O2 / N2.