It has been suggested that since the presumed biochemical evolution of life involves the formation of proteins from amino acids, a similar mechanism could perhaps have also occurred with non-carbon based amino acids. The element most chemically similar to carbon is silicon, although no silicon analogs of amino acids are known to exist. This paper reports a study of bond energetics for glycine, a hypothetical analog in which carbon atoms are replaced by silicon, and other modifications in which the glycine nitrogen and oxygen atoms are replaced by phosphorus and sulphur respectively. Comparison of energy changes are made between reactant molecules and their respective peptide bonded products. The results indicate that the peptide bond formation process is energetically feasible for glycine, but not for the proposed modifications.