The ampholytes

The ampholytes (from the Greek. amphoteros - and that and the other, lytos-soluble) - amphoteric electrolytes, i.e. a substance whose molecules contain at the same time and acid, and major groups, and therefore in aqueous solutions and dissociate as acids with the removal of hydrogen ions, H +, and as the Foundation with the removal of hydroxyl ions IT is. To ampholytes are biologically important substances: amino acids (see), peptides (see), proteins (see) and other Acidic properties of these substances due to the presence of carboxylic groups COOH, and basic properties - content amino NH2. Dissociation of molecules ampholytes in aqueous solution can be represented by the following scheme:

where R is the part of the molecule material remaining after subtracting from it the free amino and carboxyl groups.
As seen from the diagram, the ampholytes in the solution are in the form of a dipolar ions (Aminov), supporting at the same time positive and negative charges, and in the form of neutral molecules being in equilibrium with dipolar ions. The total charge dipolar ion in a neutral environment is determined by the ratio of the number of acid and major groups and their degree of dissociation.
In a strongly acid medium molecules A. positively charged:
The pH value of the environment in which molecules A., electrically neutral, called the isoelectric point and refer to pI. For A. prevailing acid properties pI lies in the region acid (pI<7); A., which is more pronounced basic properties, pI is alkaline region (PI>7). Cm. also, pH, and Electrolytes.