What is the bond that holds amino acids together?

The bond that holds amino acids together is called a peptide bond, or peptide link. A peptide bond forms during a condensation reaction, where one amino acid's carboxyl group (-COOH) reacts with another amino acid's amino group (-NH₂). This chemical reaction results in the release of a water molecule (H₂O) and creates a covalent bond between the carbon from the carboxyl group and the nitrogen from the amino group. This peptide bond links the amino acids together into a chain.

These chains of amino acids are known as polypeptides, which then fold into specific three-dimensional structures to become functional proteins. The sequence of amino acids, held together by peptide bonds, determines how the polypeptide folds, and ultimately, what role the protein plays in biological systems. Peptide bonds are therefore fundamental to protein structure and function, as they allow amino acids to be assembled in precise sequences that dictate everything from muscle contraction to enzyme activity.