The Correct Answer is Isoelectric Point. Explanation & Key Takeaways: • The pH at which the charge on protein colloid is reversed is called Isoelectric Point. • The isoelectric point is the pH of a solution or dispersion at which the net charge is zero on the molecules or colloidal particles (pI or IEP). • In electrophoresis, there is no movement at the isoelectric point of the particles in an electric field. • The net charge of any amino acid, peptide or protein (the algebraic sum of all the charged groups present) will depend on the pH of the aqueous environment surrounding it. • For Example, depending on the pH of the solution in which it is dissolved, alanine may have a charge of +1, 0, or -1. Important Notes: • Flocculation refers to the system by which fine particles are induced to clump into a floc together. • In terms of how acidic or how basic they are the pH scale is used to rate solutions. • It displays the concentration in a solution of hydrogen ions (H^(+)) and hydroxide ions (OH^(-)). • In pure water, which has a pH of 7, those ion concentrations are equal.