4. Which of the following amino acids has a      sulfur atom      in its side chain? (A) Serine (B) Lysine (C) Phenylalanine (D) Tyrosine (E) Methionine

6. You are trying to separate five proteins, which are listed below, by gel filtration chromatography. Which of the proteins will elute first from the column? (A) cytochrome c; 12 kDa (B) interferon-γ; 34 kDa (C) hemoglobin; 62 kDa (D) RNA polymerase; 99 kDa (E) glutamine synthetase; 621 kDa