What is the term used to describe the long chains formed by amino acids linked together by peptide bonds?

• A. Polypeptide chains
• B. Disulfide chains
• C. Nucleotide chains
• D. Amino acid chains

Answer: (A)

Long chains formed by amino acids linked by peptide bonds are polypeptide chains. A peptide bond forms when the amino group of one amino acid bonds with the carboxyl group of the next, creating a repeating backbone and a sequence of amino acid side chains along the chain. When many amino acids join this way, the molecule is called a polypeptide; multiple polypeptide chains can associate to form a protein. The term disulfide chains would refer to covalent disulfide linkages between cysteine residues, not the backbone chain. Nucleotide chains are the polymers of nucleotides in nucleic acids, not amino acid polymers. An "amino acid chain" is less precise than the standard term polypeptide chains, which specifically describes long chains of amino acids linked by peptide bonds.