What are amino acids linked by to form a protein?

Amino acids are linked together to form proteins through peptide bonds, which are specific types of covalent bonds that occur during a process called protein synthesis. When two amino acids come together, the carboxyl group of one amino acid reacts with the amino group of another, resulting in the release of a molecule of water (a process known as dehydration synthesis). This reaction forms the peptide bond that links the amino acids together in a chain, ultimately creating a polypeptide that folds into a functional protein.

Peptide bonds are essential because they provide the structural framework necessary for proteins to maintain their specific three-dimensional shapes and biological functions. Understanding this is crucial because the sequence and arrangement of amino acids ultimately determine the properties and functions of the protein they constitute.

The other types of bonds mentioned in the options—ester bonds, hydrogen bonds, and disulfide bonds—serve different functions in molecular biology. Ester bonds are typically found in lipids, hydrogen bonds help stabilize secondary and tertiary protein structures, and disulfide bonds play a critical role in stabilizing the three-dimensional shape of proteins by linking cysteine residues. However, none of these contribute to the formation of the primary structure of proteins, which is specifically formed by peptide bonds.