Zwitterionisch

Zwitterionisch refers to a molecule that contains both a positive and a negative electrical charge within the same molecule, but where the molecule as a whole is electrically neutral. This unique charge distribution arises from the presence of both acidic and basic functional groups within the same chemical structure.

The term "zwitterion" comes from the German word "zwitter," meaning "hermaphrodite" or "hybrid," reflecting the dual nature of its charge. The most common examples of zwitterions are amino acids. In amino acids, the amino group (-NH2) can become protonated to form a positively charged amino group (-NH3+), while the carboxyl group (-COOH) can deprotonate to form a negatively charged carboxylate group (-COO-). At a specific pH, known as the isoelectric point, the amino acid exists predominantly as a zwitterion.

Beyond amino acids, other molecules can exhibit zwitterionic character, such as certain betaines and phospholipids. The presence of a zwitterionic structure significantly influences a molecule's physical properties, including its solubility in water, its melting point, and its behavior in electric fields. Zwitterions are generally highly soluble in polar solvents like water due to their charge separation. They often have high melting points, characteristic of ionic compounds. This property is crucial in many biological processes, where the behavior of molecules like proteins and DNA is dictated by the zwitterionic nature of their constituent amino acids.