BIOCHEM 210 ADVANCED
BIOCHEMISTRY EXAM QUESTIONS
AND ANSWERS
1. Which thermodynamic quantity best explains the ‘hydrophobic effect’ leading to the
spontaneous folding of proteins in aqueous solution?
A. Enthalpy of hydrogen bonding
B. Enthalpy of van der Waals interactions
C. Entropy of the surrounding water molecules
D. Entropy of the polypeptide chain
Answer: C
Conceptual Explanation: The hydrophobic effect is driven primarily by an increase in the
entropy of the surrounding water molecules as they are released from highly ordered
‘clathrate’ structures upon the burial of nonpolar side chains.
2. In the Ramachandran plot, the values of phi and psi are restricted due to which physical
property?
A. The planar nature of the peptide bond
B. Hydrogen bonding capacity
,C. The chirality of L-amino acids
D. Steric hindrance between atoms
Answer: D
Conceptual Explanation: The Ramachandran plot shows the allowable conformations of
phi and psi angles based on avoiding steric clashes between the carbonyl oxygen, amide
hydrogen, and side-chain atoms.
3. Which of the following amino acid residues is most likely to be found in the hydrophobic
core of a globular protein?
A. Asparagine
B. Isoleucine
C. Threonine
D. Lysine
Answer: B
Conceptual Explanation: Isoleucine has a nonpolar, aliphatic side chain, making it
energetically favorable to be buried away from water in the protein core.
4. An enzyme follows Michaelis-Menten kinetics. If the concentration of substrate is equal to
3 times the Km, what is the initial velocity (v0) in terms of Vmax?
A. 0.75 Vmax
B. 0.50 Vmax
, C. 0.25 Vmax
D. 0.90 Vmax
Answer: A
Conceptual Explanation: Using v0 = (Vmax * [S]) / (Km + [S]), if [S] = 3Km, then v0 =
(Vmax * 3Km) / (4Km) = 0.75 Vmax.
5. What is the effect of 2,3-bisphosphoglycerate (2,3-BPG) on the oxygen affinity of
hemoglobin?
A. It decreases affinity by stabilizing the T-state.
B. It increases affinity by stabilizing the R-state.
C. It has no effect on oxygen affinity.
D. It increases affinity by binding to the heme iron.
Answer: A
Conceptual Explanation: 2,3-BPG binds to the central cavity of the hemoglobin tetramer
only in the T-state (deoxy state), stabilizing it and thereby promoting the release of oxygen.
6. In a Lineweaver-Burk plot, a competitive inhibitor will change which of the following?
A. The y-intercept (1/Vmax)
B. Both the x and y intercepts
C. The x-intercept (-1/Km)
BIOCHEMISTRY EXAM QUESTIONS
AND ANSWERS
1. Which thermodynamic quantity best explains the ‘hydrophobic effect’ leading to the
spontaneous folding of proteins in aqueous solution?
A. Enthalpy of hydrogen bonding
B. Enthalpy of van der Waals interactions
C. Entropy of the surrounding water molecules
D. Entropy of the polypeptide chain
Answer: C
Conceptual Explanation: The hydrophobic effect is driven primarily by an increase in the
entropy of the surrounding water molecules as they are released from highly ordered
‘clathrate’ structures upon the burial of nonpolar side chains.
2. In the Ramachandran plot, the values of phi and psi are restricted due to which physical
property?
A. The planar nature of the peptide bond
B. Hydrogen bonding capacity
,C. The chirality of L-amino acids
D. Steric hindrance between atoms
Answer: D
Conceptual Explanation: The Ramachandran plot shows the allowable conformations of
phi and psi angles based on avoiding steric clashes between the carbonyl oxygen, amide
hydrogen, and side-chain atoms.
3. Which of the following amino acid residues is most likely to be found in the hydrophobic
core of a globular protein?
A. Asparagine
B. Isoleucine
C. Threonine
D. Lysine
Answer: B
Conceptual Explanation: Isoleucine has a nonpolar, aliphatic side chain, making it
energetically favorable to be buried away from water in the protein core.
4. An enzyme follows Michaelis-Menten kinetics. If the concentration of substrate is equal to
3 times the Km, what is the initial velocity (v0) in terms of Vmax?
A. 0.75 Vmax
B. 0.50 Vmax
, C. 0.25 Vmax
D. 0.90 Vmax
Answer: A
Conceptual Explanation: Using v0 = (Vmax * [S]) / (Km + [S]), if [S] = 3Km, then v0 =
(Vmax * 3Km) / (4Km) = 0.75 Vmax.
5. What is the effect of 2,3-bisphosphoglycerate (2,3-BPG) on the oxygen affinity of
hemoglobin?
A. It decreases affinity by stabilizing the T-state.
B. It increases affinity by stabilizing the R-state.
C. It has no effect on oxygen affinity.
D. It increases affinity by binding to the heme iron.
Answer: A
Conceptual Explanation: 2,3-BPG binds to the central cavity of the hemoglobin tetramer
only in the T-state (deoxy state), stabilizing it and thereby promoting the release of oxygen.
6. In a Lineweaver-Burk plot, a competitive inhibitor will change which of the following?
A. The y-intercept (1/Vmax)
B. Both the x and y intercepts
C. The x-intercept (-1/Km)
