BIOCHEM 210 ADVANCED
COMPREHENSIVE EXAMINATION
QUESTIONS AND ANSWERS
1. Which of the following amino acids is most likely to be found in the interior of a globular
protein due to the hydrophobic effect?
A. Isoleucine
B. Arginine
C. Aspartate
D. Serine
Answer: A
Conceptual Explanation: Isoleucine has a non-polar aliphatic side chain, making it
hydrophobic and likely to be sequestered in the protein’s core to avoid water.
2. In the Michaelis-Menten model, what does the term K_m represent regarding enzyme-
substrate interaction?
A. The maximal velocity of the reaction
B. The turnover number of the enzyme
C. The substrate concentration at which the reaction rate is half of V_max
,D. The equilibrium constant for the formation of the ES complex
Answer: C
Conceptual Explanation: K_m is defined as the substrate concentration where the velocity
is half-maximal, providing an inverse measure of the enzyme’s affinity for the substrate.
3. What is the primary effect of 2,3-bisphosphoglycerate (2,3-BPG) on hemoglobin oxygen
binding?
A. It increases oxygen affinity by stabilizing the R-state
B. It catalyzes the conversion of Fe2+ to Fe3+
C. It acts as a competitive inhibitor at the heme site
D. It decreases oxygen affinity by stabilizing the T-state
Answer: D
Conceptual Explanation: 2,3-BPG binds to the central cavity of the deoxyhemoglobin (T-
state), stabilizing it and facilitating the release of oxygen to tissues.
4. Which enzyme catalyzes the rate-limiting step of glycolysis?
A. Phosphofructokinase-1
B. Pyruvate Kinase
C. Hexokinase
D. Aldolase
, Answer: A
Conceptual Explanation: Phosphofructokinase-1 (PFK-1) is the primary flux-controlling
enzyme in glycolysis, regulated allosterically by ATP, AMP, and Citrate.
5. Which of the following best describes the mechanism of uncompetitive inhibition?
A. Inhibitor binds only to the free enzyme
B. Inhibitor binds only to the enzyme-substrate (ES) complex
C. Inhibitor binds to both free enzyme and ES complex equally
D. Inhibitor covalently modifies the active site
Answer: B
Conceptual Explanation: Uncompetitive inhibitors bind only to the ES complex, reducing
both the V_max and the apparent K_m.
6. During the citric acid cycle, which enzyme produces GTP (or ATP) via substrate-level
phosphorylation?
A. Isocitrate Dehydrogenase
B. Malate Dehydrogenase
C. Succinate Dehydrogenase
D. Succinyl-CoA Synthetase
Answer: D
COMPREHENSIVE EXAMINATION
QUESTIONS AND ANSWERS
1. Which of the following amino acids is most likely to be found in the interior of a globular
protein due to the hydrophobic effect?
A. Isoleucine
B. Arginine
C. Aspartate
D. Serine
Answer: A
Conceptual Explanation: Isoleucine has a non-polar aliphatic side chain, making it
hydrophobic and likely to be sequestered in the protein’s core to avoid water.
2. In the Michaelis-Menten model, what does the term K_m represent regarding enzyme-
substrate interaction?
A. The maximal velocity of the reaction
B. The turnover number of the enzyme
C. The substrate concentration at which the reaction rate is half of V_max
,D. The equilibrium constant for the formation of the ES complex
Answer: C
Conceptual Explanation: K_m is defined as the substrate concentration where the velocity
is half-maximal, providing an inverse measure of the enzyme’s affinity for the substrate.
3. What is the primary effect of 2,3-bisphosphoglycerate (2,3-BPG) on hemoglobin oxygen
binding?
A. It increases oxygen affinity by stabilizing the R-state
B. It catalyzes the conversion of Fe2+ to Fe3+
C. It acts as a competitive inhibitor at the heme site
D. It decreases oxygen affinity by stabilizing the T-state
Answer: D
Conceptual Explanation: 2,3-BPG binds to the central cavity of the deoxyhemoglobin (T-
state), stabilizing it and facilitating the release of oxygen to tissues.
4. Which enzyme catalyzes the rate-limiting step of glycolysis?
A. Phosphofructokinase-1
B. Pyruvate Kinase
C. Hexokinase
D. Aldolase
, Answer: A
Conceptual Explanation: Phosphofructokinase-1 (PFK-1) is the primary flux-controlling
enzyme in glycolysis, regulated allosterically by ATP, AMP, and Citrate.
5. Which of the following best describes the mechanism of uncompetitive inhibition?
A. Inhibitor binds only to the free enzyme
B. Inhibitor binds only to the enzyme-substrate (ES) complex
C. Inhibitor binds to both free enzyme and ES complex equally
D. Inhibitor covalently modifies the active site
Answer: B
Conceptual Explanation: Uncompetitive inhibitors bind only to the ES complex, reducing
both the V_max and the apparent K_m.
6. During the citric acid cycle, which enzyme produces GTP (or ATP) via substrate-level
phosphorylation?
A. Isocitrate Dehydrogenase
B. Malate Dehydrogenase
C. Succinate Dehydrogenase
D. Succinyl-CoA Synthetase
Answer: D
