Is insulin a polar molecule?
Yes. All proteins are polar.
The two factors are 1) the polarity of the bonds between the atoms in the molecule, and 2) the shape of the molecule. Basically, if the bonds are non-polar, the molecule is. If the bonds are polar, but the molecule is in such a shape that they cancel each other, the molecule is non-polar. If the bonds are polar and the molecule's shape doesn't cause them to cancel, the molecule is polar.