Final answer:
The isoelectric pH is the pH at which a protein has an equal number of positive and negative charges, while the isoelectric point is the pH at which a given amino acid exists as a zwitterion and has a neutral overall charge.
Step-by-step explanation:
Isoelectric pH (pH1): The pH at which a protein has equal number of positive and negative charges is known as isoelectric pH. When subjected to an electric field the protein do not move either towards anode or cathode, hence this property is used to isolate proteins. The proteins become least soluble at pH and get precipitated. The pH of casein is 4.5 and at this pH the casein in milk curdles producing the curd.
Isoelectric pH (pH): The pH at which the positive charge on the amino acid (or any other molecule) is equal to the negative charges, is known as isoelectric pH. At this pH the net charge will be zero and hence it does not move either to positive (anode) or to negative (cathode) electrode, when subjected to an electric field. At pH1 all the molecules exists in zwitter ion form.