2.1.Amino Acids:Building Blocks of Proteins Central to this structure is the tetrahedral alpha (a) carbon(C),which is HaN-C-H covalently linked to both the amino group and the carboxyl group.Also bonded to this a-carbon is a R hydrogen and a variable side chain.It is the side chain,the so-called R group,that gives minoAcid each amino acid its identity.2.1 · Amino Acids: Building Blocks of Proteins Structure of a Typical Amino Acid • Central to this structure is the tetrahedral alpha (a) carbon (Ca ), which is covalently linked to both the amino group and the carboxyl group. Also bonded to this a-carbon is a hydrogen and a variable side chain. It is the side chain, the so-called R group, that gives each amino acid its identity