Homology principe (I)

This paper presents the principium of the homology used by the biosystems in the alpha -aminoacidic structure formation. Are presented the structures of the alpha -aminoacids from the point of view of the radical nature. In this order are presented alpha -aminoacids with alkylic radicals and with functionalised alkylic radicals, such as alcohols, carboxylic acids, amines and ureic derivatives (all these function being placed in the final position). Amino acids with ureic groups are considered peptides formed by the acylation of the aminic groups with carbamic acid, who is considered to have the simplest amino-acidic structure (being formed only by the two caracteristic function: the carboxyle and the amine) for this reason these molecules are excluded from the codification. Are presented also alpha -amino-acids containing branched alkylic radicals and cyclic alkylic radicals. Last group is the N-heterocyclic aminoacids. All structures of these series are discussed in connection with four criteria: 1. if aminoacids are or not able to form peptidic linkage (L-P), 2. if aminoacids are or not proteic (proteine formators), 3. if aminoacids are or not included in the genetic code system, and 4. if aminoacids play or not any special metabolic role.