Section: Biological and Biochemical Foundations of Living Systems

19) Which structure shows two amino acids linked by 1 peptide bond?

1. 
2. 
3. 
4. 

Amino acids are joined by a peptide bond: 1) the leading amino acid has a primary amine group to the left, 2) the peptide bond has a carbonyl group immediately following the first amino acid side chain, 3) bonded to a secondary amine leading the second amino acid side chain, and 4) the second amino acid finishes with a carboxylic acid group. Choice d) is correct.