An R-Group is a side chain attached to the α-carbon of all amino acids. It decides the chemical versatility of the amino acid. For example, some R-Groups carry a charge, creating a polar molecule. Some R-groups are hydrophobic or hydrophillic. Cysteine, in particular, has a sulphur atom in its R-group, making it capable are forming disulphide bridges which are important in many proteins tertiary structures.
- ↑ Alberts et al (2002) Molecular Biology of the Cell 4th edition.