13. How are amino acids classified based on their R group?
(A) According to their size
(B) According to their shape
(C) According to their polarity and charge at pH 7
(D) According to their ability to form hydrogen bonds

9. Histidine has the following pKa values: pK1 = 1.82, pK2 = 9.17, pKR = 6.0 Give the net charge of histidine at pH = 4 (A) 0 (B) +1 (C) +2 (D) -1

10. Which protein is involved in some neurodegenerative diseases? (A) Albumin (B) Amyloid (C) Hemoglobin (D) Myoglobin

11. Which amino acids do NOT exist in stereoisomeric forms? (A) Glycine (B) Alanine (C) Aspartic acid (D) Phenylalanine

12. How are defective proteins degraded? (A) They are degraded by proteasomes, which are not highly conserved. (B) They are first tagged by linkage to ubiquitin, a highly conserved protein. (C) They are not degraded, but are instead excreted from the cell. (D) They are degraded by an ATP-independent system.

14. Which of the following is the first antibody to appear in response to initial exposure to an antigen? (A) IgG (B) IgA (C) IgM (D) IgD

15. Which of the following chromatographic procedures is NOT used to separate proteins? (A) Ion-exchange chromatography (B) Gel filtration chromatography (C) Affinity chromatography (D) Gas chromatography

16. Which of the following is true about protein targeting in eukaryotic cells? (A) Signal sequences are always located at the carboxyl terminus of a newly synthesized protein. (B) Polypeptides with signal sequences are moved into the Golgi apparatus as they are synthesized. (C) Proteins targeted to the nucleus have an internal signal sequence cleaved once the protein is successfully targeted. (D) Proteins targeted to mitochondria and chloroplasts do not use an amino-terminal signal sequence.

17. How does electrophoresis separate proteins? (A) By differences in their primary structure (B) By differences in their tertiary structure (C) By differences in their hydrophobicity (D) By differences in their mass or charge

18. Which of the following is the major contributor to stabilizing the globular form of most soluble proteins? (A) Hydrophobic effect (B) Van der Waals interactions (C) Ionic interactions (D) Hydrogen bonds

19. Which amino acid has two chiral centers? (A) Glycine (B) Tyrosine (C) Valine (D) Isoleucine