Why does the shape of a molecule affect its function?
IT IS OFTEN THE SHAPE OF THE MOLECULE THAT DETERMINES ITS PHYSICAL AND CHEMICAL PROPERTIES. [Structure determines function]
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.