Living organisms have enzymes which are capable of linking amino acids together by creating a peptide bond between the amino acids. This process takes place in the A and P site of ribosomes in the cell during translation.
One such enzyme is called peptidyl transferase. If an organism lacks such an enzyme, synthesis of the proteins catalyzed by that particular enzyme in its cells will not take place. If amino acids cannot be joined together, then a polypeptide chain, which forms the primary structure of the protein will not be formed.