Zone electrophoresis MCQs With Answer

Zone Electrophoresis MCQs With Answer offers a focused, exam-ready practice set for M. Pharm students studying Modern Pharmaceutical Analytical Techniques. Zone electrophoresis is central to qualitative and quantitative analysis of biomolecules and pharmaceuticals—covering support media like agarose and polyacrylamide gels, as well as capillary zone electrophoresis (CZE). These questions emphasize principles (mobility, electroendosmosis, Joule heating), method components (buffers, gels, detectors), and pharmaceutical applications (protein purity, impurity profiling). Each item is designed to build conceptual clarity and practical insight, including stacking concepts in discontinuous PAGE, effects of pH and ionic strength, and optimization strategies for resolution. Use this set to solidify understanding and refine test-taking skills for university exams and research practice.

Q1. What best describes the principle of zone electrophoresis?

• Separation of analytes into discrete bands due to differences in electrophoretic mobility under an electric field
• Separation of analytes at their isoelectric points within a pH gradient
• Separation based solely on particle density in a centrifugal field
• Selective precipitation of analytes at different ionic strengths

Correct Answer: Separation of analytes into discrete bands due to differences in electrophoretic mobility under an electric field

Q2. The electrophoretic mobility (μ) of an ion in zone electrophoresis is correctly defined as:

• μ = v/E (velocity per unit electric field)
• μ = E/v
• μ = q·f (charge multiplied by frictional coefficient)
• μ = v·E

Correct Answer: μ = v/E (velocity per unit electric field)

Q3. Which factor most strongly contributes to band broadening in zone electrophoresis?

• Diffusion and longitudinal dispersion over time
• Joule heating that induces convection
• Adsorption of analyte to the support matrix
• All of the above

Correct Answer: All of the above

Q4. In paper or cellulose acetate electrophoresis, electroendosmosis primarily causes:

• Bulk flow of buffer toward the anode, sweeping neutral solutes to the anode
• Bulk flow of buffer toward the cathode, sweeping neutral solutes to the cathode
• No bulk flow; only ions migrate
• Reversal of analyte charge

Correct Answer: Bulk flow of buffer toward the cathode, sweeping neutral solutes to the cathode

Q5. In discontinuous SDS-PAGE (Laemmli system), the stacking gel’s main function is to:

• Concentrate sample into a thin zone between a fast leading ion (Cl−) and a slow trailing ion (Gly−) before size separation
• Provide small pores for high-resolution size separation
• Remove SDS from proteins to reveal native charge
• Generate a pH gradient for isoelectric focusing

Correct Answer: Concentrate sample into a thin zone between a fast leading ion (Cl−) and a slow trailing ion (Gly−) before size separation

Q6. What is the primary role of SDS in SDS-PAGE?

• To increase protein native charge and enhance mobility
• To impart a uniform negative charge density so separation is based predominantly on size
• To crosslink proteins, preventing diffusion
• To catalyze acrylamide polymerization

Correct Answer: To impart a uniform negative charge density so separation is based predominantly on size

Q7. Which statement about agarose versus polyacrylamide gels is true?

• Agarose provides larger pores useful for large nucleic acids, while polyacrylamide allows tunable pore size for proteins/peptides
• Polyacrylamide has larger pores than agarose and is better for very large DNA
• Both have identical pore structures; choice depends only on buffer
• Agarose is always superior for resolving proteins below 20 kDa

Correct Answer: Agarose provides larger pores useful for large nucleic acids, while polyacrylamide allows tunable pore size for proteins/peptides

Q8. Increasing buffer ionic strength at a fixed applied voltage in gel electrophoresis typically:

• Decreases current and reduces Joule heating
• Increases current and Joule heating, risking convection and band broadening
• Has no effect on current
• Precipitates proteins by salting out

Correct Answer: Increases current and Joule heating, risking convection and band broadening

Q9. Capillary zone electrophoresis (CZE) separates solutes primarily on the basis of:

• Differences in sedimentation coefficients in a centrifugal field
• Differences in electrophoretic mobility in free solution, often with electroosmotic flow
• Binding affinity to stationary phase
• Partitioning between immiscible solvents

Correct Answer: Differences in electrophoretic mobility in free solution, often with electroosmotic flow

Q10. A typical internal diameter for fused-silica capillaries used in CZE is:

• 1–2 mm
• 250–500 μm
• 25–75 μm
• 1–5 μm

Correct Answer: 25–75 μm

Q11. At alkaline pH in an uncoated fused-silica capillary, the direction of electroosmotic flow (EOF) is:

• From cathode to anode
• From anode to cathode
• No EOF at alkaline pH
• Random due to diffusion

Correct Answer: From anode to cathode

Q12. A commonly used on-capillary detection mode for peptides in CZE without derivatization is:

• UV absorbance at ~200–214 nm
• Refractive index detection
• Electrochemical amperometry without electrodes
• Mass spectrometry only

Correct Answer: UV absorbance at ~200–214 nm

Q13. In agarose gel serum protein electrophoresis at pH ~8.6, which fraction migrates fastest toward the anode?

• Albumin
• Gamma globulins
• Beta lipoproteins
• Alpha-2 globulins

Correct Answer: Albumin

Q14. The SI unit for electrophoretic mobility is:

• m s/V
• m/V·s
• m²/V·s
• V·s/m²

Correct Answer: m²/V·s

Q15. In both gels and capillaries, increasing the applied voltage (within thermal limits) generally:

• Increases analysis time and decreases efficiency
• Decreases analysis time and can improve efficiency until Joule heating dominates
• Has no impact on band broadening
• Always improves resolution indefinitely

Correct Answer: Decreases analysis time and can improve efficiency until Joule heating dominates

Q16. Sample overloading in zone electrophoresis most commonly leads to:

• Narrower, taller peaks with better resolution
• Zone fronting/tailing and broadened bands with poorer resolution
• Complete immobilization of analytes
• Reversal of migration direction

Correct Answer: Zone fronting/tailing and broadened bands with poorer resolution

Q17. For proteins in zone electrophoresis, which statement is correct regarding pH and net charge?

• At pH above the isoelectric point (pI), proteins are net positive and move to the cathode
• At pH above the isoelectric point (pI), proteins are net negative and move to the anode
• At pH below pI, proteins are net negative
• Protein charge is independent of pH

Correct Answer: At pH above the isoelectric point (pI), proteins are net negative and move to the anode

Q18. The primary purpose of a tracking dye such as bromophenol blue in PAGE is to:

• Bind proteins stoichiometrically for quantification
• Monitor the migration front to judge when to stop the run
• Crosslink the gel uniformly
• Increase gel conductivity

Correct Answer: Monitor the migration front to judge when to stop the run

Q19. In polyacrylamide gel casting, polymerization is initiated by which pair of reagents?

• Urea and formamide
• Ammonium persulfate (APS) and TEMED
• EDTA and Tris
• Glycine and chloride

Correct Answer: Ammonium persulfate (APS) and TEMED

Q20. For broad molecular weight protein mixtures, which gel strategy commonly improves resolution across the range?

• Use of a single low %T gel for all protein sizes
• Gradient polyacrylamide gel (e.g., 4–20%) to accommodate a wide size range
• Removing SDS to enable charge-based separation only
• Using agarose instead of polyacrylamide for all proteins

Correct Answer: Gradient polyacrylamide gel (e.g., 4–20%) to accommodate a wide size range

Download