Their defining features are an amino group (a nitrogen and two hydrogens) and a carboxylic acid group (a carbon, two oxygens and a hydrogen), both attached to the same carbon.

• 胺基酸的基本特徵是含有一个胺基（一个氮原子和两个氢原子）和一个羧基（一个碳原子、两个氧原子和一个氢原子），两个化学基连接在同一个碳原子上。