In the primary structure of a protein, amino acids are joined together by bonds.

In the primary structure of a protein, amino acids are joined together by peptide bonds otherwise called CO-NH bonds. Amino acids unite together and will form a peptide bond further it forms a polypeptide chain by combined with many peptides.

the sugar-phosphate backbone forms the structural framework of nucleic acids, including dna and rna. this backbone is composed of alternating sugar and phosphate groups, and defines directionality of the molecule.