CHM 515: BIOPHYSICAL CHEMISTRY I

BIOPHYSICAL CHEMISTRY I

QUESTIONS AND ANSWERS

Below is a set of 60 multiple-choice questions covering fundamental topics in Biophysical
Chemistry I. Each question is followed by four answer choices, the correct answer, and a brief
rationale explaining why that answer is correct.


1. Definition of Biophysical Chemistry

Question: Biophysical chemistry is best described as the study of:
A. The chemical reactions used in industrial processes.
B. The physical and chemical principles underlying biological phenomena.
C. The structure of small organic molecules.
D. Purely physical properties of non-biological materials.
Correct Answer: B
Rationale: Biophysical chemistry integrates physical chemistry methods and principles to
understand biological systems—from macromolecular structure and dynamics to interactions and
energetics.




2. Protein Structure Determination

Question: Which technique is most commonly used to obtain high-resolution (atomic level)
structures of proteins?
A. Circular dichroism (CD) spectroscopy
B. Nuclear magnetic resonance (NMR) spectroscopy
C. X-ray crystallography
D. Dynamic light scattering (DLS)
Correct Answer: C
Rationale: X-ray crystallography is the gold standard for determining high-resolution,



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,atomic-level structures of proteins, even though complementary methods (e.g., NMR, cryo-EM)
are also used.




3. Circular Dichroism (CD) Spectroscopy

Question: Far-UV CD spectroscopy is most sensitive to which aspect of protein structure?
A. Primary (amino acid sequence)
B. Secondary (α-helix and β-sheet content)
C. Tertiary (overall 3D fold)
D. Quaternary (assembly of subunits)
Correct Answer: B
Rationale: Far-UV CD (190–250 nm) probes the peptide bond electronic transitions, providing
information about the secondary structural content of proteins.




4. Fluorescence Spectroscopy

Question: In fluorescence spectroscopy, what phenomenon occurs after a molecule absorbs
light?
A. It emits light at a shorter wavelength than the absorbed light.
B. It emits light at the same wavelength as the absorbed light.
C. It emits light at a longer wavelength (lower energy) than the absorbed light.
D. It immediately undergoes photobleaching without emission.
Correct Answer: C
Rationale: The Stokes shift is the observation that the emitted fluorescence is red-shifted (longer
wavelength, lower energy) compared to the absorbed light due to vibrational relaxation.




5. Förster Resonance Energy Transfer (FRET)


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, Question: FRET is best described as:
A. The transfer of electrons between two molecules.
B. The nonradiative transfer of energy from an excited donor to an acceptor fluorophore,
dependent on their distance.
C. A technique to measure the mass of biomolecules.
D. The absorption of infrared light by molecular vibrations.
Correct Answer: B
Rationale: FRET occurs when the emission spectrum of a donor overlaps with the absorption
spectrum of an acceptor; the efficiency of energy transfer depends strongly on the donor–
acceptor distance (typically within 1–10 nm).




6. Hydrophobic Effect in Protein Folding

Question: Which driving force is most important for the folding of globular proteins in aqueous
solution?
A. Electrostatic interactions
B. Hydrophobic effect
C. Covalent bond formation
D. Van der Waals forces alone
Correct Answer: B
Rationale: The hydrophobic effect—the tendency of nonpolar residues to avoid contact with
water—is a major force that drives the collapse and folding of proteins into their native, compact
structures.




7. Differential Scanning Calorimetry (DSC)

Question: DSC is primarily used to study:
A. The electronic transitions in proteins.
B. Thermal transitions (e.g., unfolding) of biomolecules.

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