Amino Acids as Protein Building Blocks

Alpha amino acids

Always contain an amino group that is on an alpha-carbon (i.e., C-atom adjacent to the carboxyl group)

L-configuration of amino acids

NH₂ group on the left

What configurations are the amino acids in proteins

Proteins are always made of L-amino acids

Zwitterions in amino acids

Contain both acidic and basic groups, carboxylate has low proton affinity, amino has high proton affinity

What kind of proton affinity do acids and bases have?

Strong acids have weak proton affinity and lose H⁺ first, strong bases have high proton affinity and lose H⁺ last