But cysteine is actually sometimes known as a special side chain or a special amino acid because of its importance in forming those disulfide bridges. So, as we said earlier, Asparagin and glutamine contain polar carboxyamide groups. Now let's focus on two special cases that contain special side chain groups. So we have the simplest type of amino acid that is actually a chiral. And that's because the side chain group is nothing more than an H added. And so this is an acyl carbon, it will not have an enantomer because of these two identical H atoms found attached to our carbon.