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Why can amino acids act as both acids and bases?

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combustion — chemical reaction Log burning in a fire. Burning wood is an example of a chemical reaction in which wood in the presence of heat and oxygen is transformed into carbon dioxide, water vapor, and ash.

Amino acids are considered amphoteric because they contain both a basic amino group (–NH₂) and an acidic carboxyl group (–COOH) attached to the same α-carbon atom.12

Because of these two distinct functional groups, amino acids can react with both acids and bases. In aqueous solutions, they typically exist as dipolar ions known as zwitterions, which carry both positive and negative charges.13

When an amino acid is placed in an acidic environment, the negatively charged carboxylate group can accept a proton, neutralizing the negative charge. Conversely, in a basic environment, the positively charged amino group can donate a proton, neutralizing the positive charge. This ability to neutralize either added acid or base allows amino acids to function as buffers, helping to stabilize the concentration of hydrogen ions or hydroxide ions in a solution.3