Structures of hydrophobic amino acids. For each amino acid, a ball-and-stick model (top) shows the arrangement of atoms and bonds in space. A stereochemically realistic formula (middle) shows the geometric arrangement of bonds around atoms, and a Fischer projection (bottom) shows all bonds as being perpendicular for a simplified representation (see the Appendix to Chapter 1). The additional chiral center in isoleucine is indicated by an asterisk.