40. Which of the following statements about isoelectric point is TRUE? (A) An isoelectric point is the pH where a molecule has equal negative and positive charges (B) Proteins have isoelectric points but amino acids do not (C) Positive charges of a protein increase as pH increases (D) At the isoelectric point, a molecule moves to the anode in an electric field (E) Since proteins carry zero charges at isoelectric points, electrophoresis cannot separate different proteins based on isoelectric points