Amino acids share ____ chemical groups but have ____ side chains that allow for variation. The common groups are amino and ___ groups attached to an ___ carbon. Amino acids link together into a polypeptide via ____ bonds. Each polypeptide has a unique sequence. The repeating subunits interact with each other via ___ bonds to establish ___ structures. Interactions between the side chains determine the ___ structure of the polypeptide. The combination allows for an almost infinite number of possible structures, each with a different function.