Exam 1

Question 1

Which of the following biological molecules are highly versatile?
a. proteins
b. carbohydrates
c. water
d. lipids
e. nucleic acids

Answer 1

a. proteins

Question 2

Which of the following enzyme is responsible for phosphodiester bond formation?

a. Ligase
b. Glycogen synthase
c. DNA or RNA polymerase
d. Acyltransferase
e. Peptidyltransferase

Answer 2

c. DNA or RNA polymerase

Question 3

Which of the following is necessarily characterized by a non-covalent linkage?

a. Ionic bond
b. Ester bond
c. Glycosidic bond
d. Peptide bond
e. Phosphodiester bond

Answer 3

a. Ionic bond

Question 4

The bonds that are broken when water vaporizes are:

a. hydrogen bonds between water molecules.
b. polar covalent bonds.
c. ionic bonds.
d. covalent bonds between atoms within water molecules.
e. nonpolar covalent bonds.

Answer 4

a. hydrogen bonds between water molecules.

Question 5

What is the pH of HCl solution with a concentration of 5 mM HCl (hydrochloric acid)?

Answer 5

2.3 (pH=-log(concentration of H+ ion))

Question 6

A solution of acetic acid (pKa = 4.75) has a pH of 6.75. The ratio of acid to conjugate base is __________.

Answer 6

1 CH3COOH to 100 CH3COO-

Question 7

A patient with metabolic acidosis has a low urine pH of 5. What is the hydrogen ion concentration in the patient’s urine sample?

Answer 7

10^-5 M

Question 8

Proline is called “alpha-helix breaker” because of its:

a. side chain bonded to both the α-carbon and the nitrogen atom, limiting the rotation.
b. bulky side chain, which interferes with the backbone of the preceding turn.
Incorrect branch-side chain, which interferes with the backbone of the preceding turn.
c. charged side chain, which interferes with the backbone of the preceding turn.
d. hydrophobic side chain, which interferes with the backbone of the preceding turn.

Answer 8

a. side chain bonded to both the α-carbon and the nitrogen atom, limiting the rotation.

Question 9

Which kind of amino acids would most likely cluster in the interior of globular proteins?

a. positively charged amino acids
b. negatively charged amino acids
c. hydrophobic amino acids with nonpolar R groups
d. polar amino acids
e. none of the above

Answer 9

c. hydrophobic amino acids with nonpolar R groups

Question 10

What kind of amino acids are most likely to be found in the core of a water-soluble globular protein?

a. positively charged
b. negatively charged
c. hydrophobic
d. polar but uncharged

Answer 10

c. hydrophobic

Question 11

A peptide bond:
a. has a partial double-bond character
b. is cleaved by agents that denature proteins, such as organic solvents and high concentration of urea
c. is unstable to heating
d. ionized at physiologic pH
e. occurs most commonly in the cis configuration

Answer 11

a. has a partial double-bond character

Question 12

What amino acid is involved in disulfide bond formation?

a. phenylalanine
b. cysteine
c. isoleucine
d. theronine
e. alanine

Answer 12

b. cysteine

Question 13

The secondary structure of protein is primarily maintained by:

a. ionic bond
b. hydrophobic bond
c. van der Waals force
d. hydrogen bonds
e. peptide bond

Answer 13

d. hydrogen bonds

Question 14

Protein is denatured by heat due to the disruption of the following bonds except:

a. hydrogen bond
b. disulfide bond
c. ionic bond
d. hydrophobic interaction
e. van der Waals interaction

Answer 14

b. disulfide bond

Question 15

In sickle cell anemia, the basis of the malfunction of the hemoglonbin molecule is:

a. substitution of a single amino acid
b. faulty binding of the heme groups
c. reduced affinity for oxygen
d. Insufficient iron in the diet
e. incorrect secondary structure

Answer 15

a. substitution of a single amino acid