help check if these are right please

4. Which of these peptides has three positively charged groups at neutral pH? A) VAL-SER-GLU-GLU-PRO B) LYS-CYS-ALA-ALA-LYS C) LYS-ARG-HIS D) ASP-GLU-GLU-GLY E) ASN-GLN-GLN-GLY 5. Column chromatography that separates proteins on the basis of their charge is called: A) affinity chromatography B) ion exchange chromatography C) size exclusion chromatography D) dialysis chromatography E) green fluorescent chromatography 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 NH4/ 3. The peptide alanylglutamylglycylalanylleucine has: A) a disulfide bridge. B) five peptide bonds. C) four peptide bonds. D) no free carboxyl group. E) two free amino groups