BIOCHEM 210 COMPREHENSIVE EXAM
(MODULES 1-8) EXAM QUESTIONS AND
ANSWERS
1. Which of the following properties of water allows it to act as an effective solvent for
biological molecules?
A. Its low molecular weight
B. Its ability to form hydrogen bonds and its polar nature
C. Its high density in liquid form
D. Its lack of reactivity with organic acids
Answer: B
Conceptual Explanation: Water’s polarity and hydrogen bonding capability allow it to
dissolve polar and ionic substances by surrounding them with hydration shells.
2. According to the Henderson-Hasselbalch equation, when the pH of a solution equals the
pKa of a weak acid, what is the ratio of conjugate base to acid?
A. 10:1
B. 1:1
C. 1:10
,D. 2:1
Answer: B
Conceptual Explanation: The equation is pH = pKa + log([A-]/[HA]). If pH = pKa, then
log([A-]/[HA]) = 0, meaning [A-]/[HA] = 1.
3. Which amino acid is classified as non-polar and contains a thioether group?
A. Methionine
B. Cysteine
C. Serine
D. Threonine
Answer: A
Conceptual Explanation: Methionine is a non-polar amino acid that contains a sulfur atom
in a thioether linkage (C-S-C). Cysteine contains a thiol group (S-H).
4. The primary force stabilizing the alpha-helix secondary structure of proteins is:
A. Ionic interactions between R-groups
B. Hydrogen bonding between the carbonyl oxygen and amide nitrogen of the peptide
backbone
C. Disulfide bridges
D. Hydrophobic interactions between non-polar side chains
, Answer: B
Conceptual Explanation: Alpha-helices are stabilized by hydrogen bonds between the
C=O of one amino acid and the N-H of another amino acid four residues away in the
backbone.
5. Which of the following best describes the ‘Hydrophobic Effect’ in protein folding?
A. The formation of covalent bonds between hydrophobic residues.
B. Water molecules forming highly ordered cages around non-polar side chains, leading to
an increase in entropy when these side chains cluster together.
C. The repulsion between water and polar side chains.
D. The attraction between charged R-groups and water molecules.
Answer: B
Conceptual Explanation: The hydrophobic effect is driven by an increase in the entropy of
water. When non-polar residues cluster, fewer water molecules are constrained in
‘clathrate’ cages.
6. In the Michaelis-Menten enzyme kinetics model, the constant Km represents:
A. The maximum velocity of the reaction
B. The substrate concentration at which the reaction velocity is half of Vmax
C. The enzyme concentration at which Vmax is reached
D. The turnover number of the enzyme
(MODULES 1-8) EXAM QUESTIONS AND
ANSWERS
1. Which of the following properties of water allows it to act as an effective solvent for
biological molecules?
A. Its low molecular weight
B. Its ability to form hydrogen bonds and its polar nature
C. Its high density in liquid form
D. Its lack of reactivity with organic acids
Answer: B
Conceptual Explanation: Water’s polarity and hydrogen bonding capability allow it to
dissolve polar and ionic substances by surrounding them with hydration shells.
2. According to the Henderson-Hasselbalch equation, when the pH of a solution equals the
pKa of a weak acid, what is the ratio of conjugate base to acid?
A. 10:1
B. 1:1
C. 1:10
,D. 2:1
Answer: B
Conceptual Explanation: The equation is pH = pKa + log([A-]/[HA]). If pH = pKa, then
log([A-]/[HA]) = 0, meaning [A-]/[HA] = 1.
3. Which amino acid is classified as non-polar and contains a thioether group?
A. Methionine
B. Cysteine
C. Serine
D. Threonine
Answer: A
Conceptual Explanation: Methionine is a non-polar amino acid that contains a sulfur atom
in a thioether linkage (C-S-C). Cysteine contains a thiol group (S-H).
4. The primary force stabilizing the alpha-helix secondary structure of proteins is:
A. Ionic interactions between R-groups
B. Hydrogen bonding between the carbonyl oxygen and amide nitrogen of the peptide
backbone
C. Disulfide bridges
D. Hydrophobic interactions between non-polar side chains
, Answer: B
Conceptual Explanation: Alpha-helices are stabilized by hydrogen bonds between the
C=O of one amino acid and the N-H of another amino acid four residues away in the
backbone.
5. Which of the following best describes the ‘Hydrophobic Effect’ in protein folding?
A. The formation of covalent bonds between hydrophobic residues.
B. Water molecules forming highly ordered cages around non-polar side chains, leading to
an increase in entropy when these side chains cluster together.
C. The repulsion between water and polar side chains.
D. The attraction between charged R-groups and water molecules.
Answer: B
Conceptual Explanation: The hydrophobic effect is driven by an increase in the entropy of
water. When non-polar residues cluster, fewer water molecules are constrained in
‘clathrate’ cages.
6. In the Michaelis-Menten enzyme kinetics model, the constant Km represents:
A. The maximum velocity of the reaction
B. The substrate concentration at which the reaction velocity is half of Vmax
C. The enzyme concentration at which Vmax is reached
D. The turnover number of the enzyme
