Site pages
Current course
Participants
General
Topic 1
Topic 2
Topic 3
Topic 4
Topic 5
Topic 6
Topic 7
Topic 8
Topic 9
Topic 10
Topic 11
Topic 12
Topic 13
Topic 14
Topic 15
Topic 16
Topic 17
Topic 18
Topic 19
Topic 20
Topic 21
Topic 22
Topic 23
Topic 24
Topic 25
Topic 26
Topic 27
5.3.1.1 Amphoteric Property
Many substances contain acidic and basic groups and react with both acids and bases to form salts. Such property is called an amphoteric property and the substances are called ampholytes. Notable among these are the amino acids of which the proteins are composed. Proteins like amino acids exist in solution as zwitterions and have isoelectric pH values at which they are least soluble and migrate least in an electric field.
Above the isoelectric pH they act as acids and form negative protein ions, whereas below the isoelectric pH they act as bases and form positive ions. Because protein molecules contain number of groups that interact reversibly with H + ions over a vide range of pH, their solutions have excellent buffer action, and much of the buffer capacity of body tissues is due to the protein buffers Protein+ ↔ H+ -Protein+ ↔ H+ + Protein- Cation Zwitterion anion |