5. The two peptides shown in the figure below are linked through _____ (A) an ester linkage (B) a disulfide bond (C) a peptide bond (D) a glycosidic bond (E) a hydrogen bond.

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