Classification of Amino Acids

Table 10.2 Classification of amino acids based on chemical structure...

Classification of amino acids. Arginine and histidine are essential under some conditions. 

The inability of mammals to synthesize all of the amino acids they require has led to the classification of amino acids as essential and nonessential. Conceptually this distinction seems clear. Practically speaking, it turns out to be more complex to designate essential amino acids. An essential amino acid, in this classification, means one that must be supplied in the diet if the organism is to maintain a positive nitrogen balance. As we will see, the absence of a de novo pathway for the biosynthesis of an amino acid does... 

TABLE 11.1. Classification of Amino Acids According to their Biochemical Properties... 

Table 20.7 Classification of Amino Acids on the Basis of Their Metabolic Fate...

The protein amino acids are classified according to the chemical nature of their R groups as aliphatic, aromatic, heterocyclic and sulphur containing amino acids. More meaningful classification of amino acids is based on the polarity of the R groups. The polarity of the R groups varies widely from totally non-polar to highly polar. The 20 amino acids are classified into four main classes. 

Table 3.2. Classification of Amino Acids as Mainly Polar or Nonpolara...

TABLE 14.2 Classification of amino acids according to their biochemical properties... 

Classification of amino acids into biosynthetic families emphasizes the common origin of related metabolites and is conceptually useful in delineating regulatory relationships. Lysine, threonine, methionine, and isoleucine comprise a family of amino acids originating with aspartate. However, isoleucine is also structurally and metabolically related to the branched-chain amino acids, leucine and valine. The latter two amino acids, along with alanine, are members of the pyruvate family. The common metabolic pre-... 

Table 7.1 Classification of amino acids in the human diet...

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