So what exactly is the difference between these here and methionine? Well, unlike these, the methionine side chain contains a sulfur atom. Now, what's the electronegativity of sulfur as compared to the carbon? So the electronegativity of carbon is 2.55, and the electronegativity of sulfur is 2.58. And those values and those values are essentially the same. And that's exactly why these bonds are non polar.