BioChem 170 Final Exam - Portage Learning |
() |: Multiple Choice (1–100)
*Select one best answer. Each correct answer = 1 point.*
1. Which property of water is most critical for maintaining cellular temperature
homeostasis?
a) High heat of vaporization
b) High specific heat capacity
c) Low viscosity
d) Nonpolar nature
Answer: b) High specific heat capacity
Rationale: High specific heat allows water to absorb or release large amounts of heat with
minimal temperature change, stabilizing cellular environments.
2. The Henderson-Hasselbalch equation is used to calculate:
a) Enzyme turnover number
b) pH of a buffer solution
c) Free energy change of a reaction
d) Protein isoelectric point
Answer: b) pH of a buffer solution
Rationale: pH = pKa + log([A-]/[HA]) relates pH, pKa, and ratio of conjugate base to acid.
3. Which amino acid side chain is most likely to be found in the interior of a globular
protein?
a) Lysine
b) Arginine
c) Leucine
d) Aspartate
Answer: c) Leucine
Rationale: Leucine is hydrophobic (nonpolar); interior packing minimizes contact with water.
4. The peptide bond is best described as:
a) Completely flexible, allowing free rotation
, b) Planar and rigid due to partial double-bond character
c) Irreversible under all cellular conditions
d) Formed by a dehydration reaction between two sulfhydryl groups
Answer: b) Planar and rigid due to partial double-bond character
Rationale: Resonance between C=O and N gives ~40% double-bond character, restricting
rotation.
5. An enzyme that catalyzes the transfer of a phosphate group from ATP to a substrate
is a:
a) Hydrolase
b) Lyase
c) Kinase
d) Isomerase
Answer: c) Kinase
Rationale: Kinases specifically transfer phosphate groups from high-energy donors like ATP.
6. In competitive inhibition:
a) Vmax decreases, Km unchanged
b) Vmax unchanged, Km increases
c) Both Vmax and Km decrease
d) Both Vmax and Km increase
Answer: b) Vmax unchanged, Km increases
Rationale: Inhibitor competes for active site; higher substrate overcomes inhibition → same
Vmax, but apparent affinity (1/Km) drops.
7. The committed step of glycolysis in most cells is catalyzed by:
a) Hexokinase
b) Phosphofructokinase-1 (PFK-1)
c) Glyceraldehyde-3-phosphate dehydrogenase
d) Pyruvate kinase
Answer: b) Phosphofructokinase-1 (PFK-1)
Rationale: PFK-1 is the major regulatory point; it is allosterically inhibited by ATP and citrate,
activated by AMP/fructose-2,6-bisP.
8. Under anaerobic conditions in muscle, pyruvate is converted to:
a) Acetyl-CoA
b) Ethanol
c) Lactate
d) Oxaloacetate
, Answer: c) Lactate
Rationale: Lactate dehydrogenase reduces pyruvate to lactate, regenerating NAD+ for
glycolysis to continue.
9. The TCA cycle occurs in which cellular compartment?
a) Cytosol
b) Mitochondrial matrix
c) Inner mitochondrial membrane
d) Nucleus
Answer: b) Mitochondrial matrix
Rationale: Enzymes of the citric acid cycle (except succinate dehydrogenase which is
membrane-bound) are in the matrix.
10. During oxidative phosphorylation, ATP synthesis is driven by:
a) Substrate-level phosphorylation
b) Proton motive force across inner mitochondrial membrane
c) Direct transfer of phosphate from NADH
d) Decarboxylation of isocitrate
Answer: b) Proton motive force across inner mitochondrial membrane
Rationale: Electron transport pumps H+ out → gradient → ATP synthase uses flow back in to
make ATP.
*(Questions 11–100 follow similar structure, covering: pH calculations, buffer systems,
protein folding, SDS-PAGE, Michaelis-Menten, allostery, glycolysis intermediates,
gluconeogenesis bypass enzymes, pentose phosphate pathway, beta-oxidation, ketone
bodies, urea cycle, transamination, DNA replication, transcription, translation, Lac operon,
ELISA, Western blotting, etc. Full set available upon request for brevity; here representative
examples are shown.)*
Section II: Matching (101–130)
Match the term in Column A with the correct description in Column B. (1 point each)
Column A Column B
101. Chaperonin A. Inhibits aconitase in TCA cycle
102. Fluoroacetate B. Assists protein folding under ATP
() |: Multiple Choice (1–100)
*Select one best answer. Each correct answer = 1 point.*
1. Which property of water is most critical for maintaining cellular temperature
homeostasis?
a) High heat of vaporization
b) High specific heat capacity
c) Low viscosity
d) Nonpolar nature
Answer: b) High specific heat capacity
Rationale: High specific heat allows water to absorb or release large amounts of heat with
minimal temperature change, stabilizing cellular environments.
2. The Henderson-Hasselbalch equation is used to calculate:
a) Enzyme turnover number
b) pH of a buffer solution
c) Free energy change of a reaction
d) Protein isoelectric point
Answer: b) pH of a buffer solution
Rationale: pH = pKa + log([A-]/[HA]) relates pH, pKa, and ratio of conjugate base to acid.
3. Which amino acid side chain is most likely to be found in the interior of a globular
protein?
a) Lysine
b) Arginine
c) Leucine
d) Aspartate
Answer: c) Leucine
Rationale: Leucine is hydrophobic (nonpolar); interior packing minimizes contact with water.
4. The peptide bond is best described as:
a) Completely flexible, allowing free rotation
, b) Planar and rigid due to partial double-bond character
c) Irreversible under all cellular conditions
d) Formed by a dehydration reaction between two sulfhydryl groups
Answer: b) Planar and rigid due to partial double-bond character
Rationale: Resonance between C=O and N gives ~40% double-bond character, restricting
rotation.
5. An enzyme that catalyzes the transfer of a phosphate group from ATP to a substrate
is a:
a) Hydrolase
b) Lyase
c) Kinase
d) Isomerase
Answer: c) Kinase
Rationale: Kinases specifically transfer phosphate groups from high-energy donors like ATP.
6. In competitive inhibition:
a) Vmax decreases, Km unchanged
b) Vmax unchanged, Km increases
c) Both Vmax and Km decrease
d) Both Vmax and Km increase
Answer: b) Vmax unchanged, Km increases
Rationale: Inhibitor competes for active site; higher substrate overcomes inhibition → same
Vmax, but apparent affinity (1/Km) drops.
7. The committed step of glycolysis in most cells is catalyzed by:
a) Hexokinase
b) Phosphofructokinase-1 (PFK-1)
c) Glyceraldehyde-3-phosphate dehydrogenase
d) Pyruvate kinase
Answer: b) Phosphofructokinase-1 (PFK-1)
Rationale: PFK-1 is the major regulatory point; it is allosterically inhibited by ATP and citrate,
activated by AMP/fructose-2,6-bisP.
8. Under anaerobic conditions in muscle, pyruvate is converted to:
a) Acetyl-CoA
b) Ethanol
c) Lactate
d) Oxaloacetate
, Answer: c) Lactate
Rationale: Lactate dehydrogenase reduces pyruvate to lactate, regenerating NAD+ for
glycolysis to continue.
9. The TCA cycle occurs in which cellular compartment?
a) Cytosol
b) Mitochondrial matrix
c) Inner mitochondrial membrane
d) Nucleus
Answer: b) Mitochondrial matrix
Rationale: Enzymes of the citric acid cycle (except succinate dehydrogenase which is
membrane-bound) are in the matrix.
10. During oxidative phosphorylation, ATP synthesis is driven by:
a) Substrate-level phosphorylation
b) Proton motive force across inner mitochondrial membrane
c) Direct transfer of phosphate from NADH
d) Decarboxylation of isocitrate
Answer: b) Proton motive force across inner mitochondrial membrane
Rationale: Electron transport pumps H+ out → gradient → ATP synthase uses flow back in to
make ATP.
*(Questions 11–100 follow similar structure, covering: pH calculations, buffer systems,
protein folding, SDS-PAGE, Michaelis-Menten, allostery, glycolysis intermediates,
gluconeogenesis bypass enzymes, pentose phosphate pathway, beta-oxidation, ketone
bodies, urea cycle, transamination, DNA replication, transcription, translation, Lac operon,
ELISA, Western blotting, etc. Full set available upon request for brevity; here representative
examples are shown.)*
Section II: Matching (101–130)
Match the term in Column A with the correct description in Column B. (1 point each)
Column A Column B
101. Chaperonin A. Inhibits aconitase in TCA cycle
102. Fluoroacetate B. Assists protein folding under ATP
