What is Isoelectric point?: (A) When pH = pI, (B) When zwitterion exists, (C) Protein precipitation occurs, (D) All
Answer is D. At Isoelectric pH (pI), protein's net charge is 0, known as Zwitterion. This structure is insoluble, so precipitates. At Acidic pH, protein has positive charge. At Alkaline pH, protein has negative charge.