2. An acid is added to a solution containing the amino acid leucine. As the pH decreases from pH=4.0 to pH=1.0, what happens during this time? A) the COOH groups will become negatively charged B) the COOgroups will go from negatively charged to neutral C) the net charge on the amino acids will go from +1 to 0 D) the amino groups will go from NH2 to NH3+ E) the amino groups will go from NH3+to NH2