zwitterion

chemistry

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July 15, 2026

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A zwitterion is a dipolar ion, meaning it carries an equal number of positive and negative charges. This type of ion is also referred to as an amphoteric ion.12

Amino acids, fundamental building blocks of proteins, are a common example of molecules that exist as zwitterions. In solution, they possess both a basic amino group and an acidic carboxyl group. At physiological pH, these groups become ionized, resulting in a molecule with a net zero charge. This specific pH at which a molecule has an equal number of positive and negative charges is called the isoelectric point.3

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liquid
Solutions of electrolytes
…the other is called a zwitterion. Very large molecules, such as those of proteins, may have numerous positive and negative charges; such molecules are called polyelectrolytes. In solution, the conformation (i.e., the three-dimensional structure) of a large, charged molecule is strongly dependent on the ionic strength of the dissolving medium;…
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…the other is called a zwitterion. Very large molecules, such as those of proteins, may have numerous positive and negative charges; such molecules are called polyelectrolytes. In solution, the conformation (i.e., the three-dimensional structure) of a large, charged molecule is strongly dependent on the ionic strength of the dissolving medium;…
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carboxylic acid
Amino acids
…of internal salts known as zwitterions (from German zwitter, “hybrid”). Because they are internal salts, amino acids are all solids at room temperature, and most of them are soluble in water.
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…of internal salts known as zwitterions (from German zwitter, “hybrid”). Because they are internal salts, amino acids are all solids at room temperature, and most of them are soluble in water.
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organosulfur compound
Sulfonium and oxosulfonium salts; sulfur ylides
…is an example of a zwitterion, a compound that is an internal ion pair; in the name of this compound, “dimethylsulfonium” precedes the name of the root compound. In the above examples of sulfonium salts, sulfur is bonded to three carbon groups, but sulfonium salts are known in which one…
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…is an example of a zwitterion, a compound that is an internal ion pair; in the name of this compound, “dimethylsulfonium” precedes the name of the root compound. In the above examples of sulfonium salts, sulfur is bonded to three carbon groups, but sulfonium salts are known in which one…
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