BIOMOLECULES AND ENZYMES

Detailed explanation-1: -Amino acids are ampholytes; i.e., they contain both acidic and basic groups. Free amino acids can never occur as nonionic molecules. Instead, they exist as neutral zwitterions that contain both positively and negatively charged groups. Zwitterions are electrically neutral and so do not migrate in an electric field.

Detailed explanation-2: -Amino acids can act as both an acid and a base due to the presence of the amino and carboxyl functional groups. The pH at which a given amino acid exists in solution as a zwitterion is called the isoelectric point (pI).

Detailed explanation-3: -Hence they behave as acids in an alkaline medium and bases in an acidic medium. So, amino acids are amphoteric.

Detailed explanation-4: -Amino acids are amphoteric: they can react as either an acid or a base. Ammonium ion acts as an acid, the carboxylate as a base.

Detailed explanation-5: -The imidazole side chain of histidine allows it to function in both acid and base catalysis near physiological pH values. None of the other standard amino acids possesses this important chemical property. Therefore, histidine is an amino acid that most often makes up the active sites of protein enzymes.