QUIZ 1, BICH 410( MWF 1:50 PM), Friday, Sept. 16, 1994
Clearly circle the letter corresponding to your answer for each problem. There are six problems and each count 3 points. You get two free points for this quiz. No partial credit given for multiple-choice questions.
1. The three-dimensional structure of macromolecules is formed and maintained primarily through noncovalent interactions. Which of the following is not considered a noncovalent interaction?
- A. hydrogen bonds
- B. disulfide bonds
- C. hydrophobic interactions
- D. van der Waals interactions
- E. ionic interactions
2. Phosphoric acid (H3PO4) has three ionizable protons, with pKas of 2.14, 6.86, and 12.4. The ionic form that predominates at pH 8.5 is:
- A. H3PO4
- B. H2PO4-
- C. HPO4-2
- D. PO4-3
3. What functional group is not present in tyrosine?
- A. carboxyl
- B. benzene ring
- C. hydroxyl
- D. amide
- E. amino
4. The pH of a sample of blood is 7.4. The pH of a sample of gastric juice is 1.4. The blood sample has:
- A. 6 times lower [H+] than the gastric juice.
- B. 6 times higher [H+] than the gastric juice.
- C. a million times lower [H+] than the gastric juice.
- D. a million times higher [H+] than the gastric juice.
- E. none of the above
5. For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will:
- A. have a net positive charge.
- B. have a net negative charge.
- C. show no net charge.
- D. have negative and positive charges in equal concentration.
- E. be neutral with no charged groups.
6. Fifty mL of 0.1 M NaOH is added to 100 mL of 0.1 M lactic acid. Lactic acid has a pKa of 4.1. The resulting mixture has a pH close to: