Assessment of biological activity and potency MCQs With Answer

Introduction

This quiz collection on “Assessment of Biological Activity and Potency” is tailored for M.Pharm students preparing for advanced coursework and exams in Biological Evaluation of Drug Therapy. It covers core principles—definitions of potency and efficacy, dose–response analysis, ED50/EC50/IC50 concepts, graded versus quantal responses, receptor theory, and experimental bioassay designs. Emphasis is on practical assay types (in vivo and in vitro), statistical approaches (parallel-line, probit, Spearman-Karber), and parameters used to validate bioassays (sensitivity, precision, accuracy, linearity). Questions are designed to deepen conceptual understanding and application of methods used to quantify biological activity and compare potencies of therapeutic agents.

Q1. Which statement best distinguishes potency from efficacy in pharmacological bioassays?

• Potency refers to the maximum response a drug can produce, while efficacy denotes the dose required to produce that response.
• Potency indicates the relative dose required to produce a defined effect, whereas efficacy denotes the maximum intrinsic effect achievable regardless of dose.
• Potency and efficacy are interchangeable terms describing the therapeutic index of a drug.
• Efficacy measures time to onset of action while potency measures duration of action.

Correct Answer: Potency indicates the relative dose required to produce a defined effect, whereas efficacy denotes the maximum intrinsic effect achievable regardless of dose.

Q2. In a graded dose–response curve, EC50 is defined as:

• The dose producing 100% of maximal effect.
• The concentration producing 50% of the maximal effect.
• The dose that is lethal to 50% of the population.
• The slope of the dose–response relationship.

Correct Answer: The concentration producing 50% of the maximal effect.

Q3. Which bioassay method is most appropriate to determine relative potency when test and standard dose–response lines are parallel?

• Schild analysis.
• Parallel line assay (PLA).
• Isobolographic analysis.
• Probit analysis for quantal data.

Correct Answer: Parallel line assay (PLA).

Q4. A Schild plot is primarily used to determine which of the following?

• Whether a competitive antagonist exists and its equilibrium dissociation constant (KB) or pA2 value.
• The LD50 of a compound in animal models.
• The steepness (Hill coefficient) of an agonist’s dose–response curve.
• The time-dependent desensitization of receptors.

Correct Answer: Whether a competitive antagonist exists and its equilibrium dissociation constant (KB) or pA2 value.

Q5. In a quantal bioassay, which statistical method is commonly used to estimate ED50 from binary response data?

• Linear regression on raw doses.
• Probit or logit analysis.
• Kaplan–Meier survival analysis.
• Schild regression.

Correct Answer: Probit or logit analysis.

Q6. When comparing two agonists, one shows a left-shifted dose–response curve with the same maximal response as the other. This indicates that the left-shifted agonist is:

• Less potent but more efficacious.
• More potent with similar efficacy.
• Less efficacious and less potent.
• More efficacious but less potent.

Correct Answer: More potent with similar efficacy.

Q7. Inhibition constant (IC50) values depend on experimental conditions. Which statement explains why comparing IC50 across different assays can be misleading?

• IC50 is a universal constant and does not change with conditions.
• IC50 depends on substrate or agonist concentration and assay sensitivity, so differing conditions shift IC50 values.
• IC50 measures potency only for irreversible antagonists, so comparisons are invalid for reversible inhibitors.
• IC50 directly equals KB and therefore is independent of receptor reserve.

Correct Answer: IC50 depends on substrate or agonist concentration and assay sensitivity, so differing conditions shift IC50 values.

Q8. Which parameter of a bioassay describes its ability to produce consistent results under unchanged conditions when repeated measurements are taken?

• Accuracy.
• Sensitivity.
• Precision (repeatability).
• Specificity.

Correct Answer: Precision (repeatability).

Q9. The presence of spare receptors in a tissue will most likely affect which aspect of the dose–response relationship?

• It increases maximal efficacy above receptor occupancy limits.
• It reduces potency (requires higher agonist concentration for the same effect).
• It allows a near-maximal response at submaximal receptor occupancy, increasing apparent potency.
• It abolishes the effect of competitive antagonists completely.

Correct Answer: It allows a near-maximal response at submaximal receptor occupancy, increasing apparent potency.

Q10. Which validation parameter ensures that an assay response is due only to the analyte of interest and not to other components?

• Linearity.
• Limit of detection.
• Specificity (selectivity).
• Precision.

Correct Answer: Specificity (selectivity).

Q11. In a parallel line potency assay, non-parallelism indicates what about the test and standard dose–response relationships?

• They have identical slopes and therefore can be compared directly for potency.
• They have different slopes indicating possible differences in mechanism, efficacy, or assay artifacts, so potency estimation is invalid.
• Non-parallelism suggests both curves are too noisy to analyze.
• Non-parallelism confirms identical potency but differing precision.

Correct Answer: They have different slopes indicating possible differences in mechanism, efficacy, or assay artifacts, so potency estimation is invalid.

Q12. For an antagonist that produces a parallel rightward shift of the agonist dose–response curve without reducing maximal response, the antagonist is most likely:

• Noncompetitive irreversible antagonist.
• Allosteric agonist.
• Competitive reversible antagonist.
• Partial agonist behaving as an antagonist.

Correct Answer: Competitive reversible antagonist.

Q13. Which approach is best for estimating LD50 in a small animal study with quantal mortality data?

• Schild plot analysis.
• Spearman–Kärber or Reed–Muench methods.
• Hill equation fitting for graded responses.
• ANOVA for continuous outcomes.

Correct Answer: Spearman–Kärber or Reed–Muench methods.

Q14. The Hill coefficient (nH) derived from fitting a Hill equation to a dose–response curve primarily informs you about:

• Maximal efficacy of the drug.
• Cooperativity of ligand–receptor interactions and slope of the curve.
• Absolute potency expressed as EC100.
• The time to reach steady-state concentration.

Correct Answer: Cooperativity of ligand–receptor interactions and slope of the curve.

Q15. When validating an in vitro bioassay for potency estimation, which attribute assesses the smallest concentration change that can be reliably detected?

• Specificity.
• Linearity range.
• Limit of quantitation (LOQ) or analytical sensitivity.
• Intra-assay variability.

Correct Answer: Limit of quantitation (LOQ) or analytical sensitivity.

Q16. In an isobologram for two drugs with additive interaction, the point representing an effective combination will fall:

• On the straight line connecting the ED50 of each drug (the line of additivity).
• Above the line of additivity indicating synergism.
• Below the line of additivity indicating antagonism.
• At the origin irrespective of dose.

Correct Answer: On the straight line connecting the ED50 of each drug (the line of additivity).

Q17. Which of the following best describes a biological standard used in potency assays?

• A random batch of the test formulation used to calibrate instruments.
• A well-characterized reference preparation with assigned potency used to calibrate or compare test samples.
• An internal blank used to zero the assay response.
• An unrelated compound used as a negative control.

Correct Answer: A well-characterized reference preparation with assigned potency used to calibrate or compare test samples.

Q18. Which factor most reduces assay variability when conducting repeated bioassays over time?

• Using different operators and variable incubation times.
• Standardizing reference standards, protocols, and environmental conditions; strong QC practices.
• Changing tissue sources frequently to avoid adaptation.
• Altering assay endpoints between runs to obtain diverse data.

Correct Answer: Standardizing reference standards, protocols, and environmental conditions; strong QC practices.

Q19. A partial agonist shows lower maximal response than a full agonist. In the presence of a full agonist, a partial agonist will:

• Always increase the maximal response further.
• Act as an antagonist and reduce the maximal response by competing for receptors.
• Have no interaction and produce additive maximal responses.
• Convert the full agonist into an inverse agonist.

Correct Answer: Act as an antagonist and reduce the maximal response by competing for receptors.

Q20. When reporting potency estimates from a bioassay, which practice best supports regulatory acceptance and scientific reproducibility?

• Reporting only the ED50 value without confidence intervals or assay conditions.
• Providing ED50/EC50 with 95% confidence intervals, assay conditions, calibration details, and validation metrics.
• Using proprietary calculations without describing methodology.
• Pooling data from different assay types without stratification or rationale.

Correct Answer: Providing ED50/EC50 with 95% confidence intervals, assay conditions, calibration details, and validation metrics.

Download