Bioassay of ACTH MCQs With Answer

Bioassay of ACTH MCQs With Answer

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Bioassay of ACTH MCQs With Answer is a concise, student-focused primer for B.Pharm learners covering adrenocorticotropic hormone bioassays, assay design, potency estimation and validation. This introduction highlights key keywords: ACTH, bioassay, potency, ED50, reference standard, sensitivity, specificity, in vivo and in vitro methods, adrenal cell assays, immunoassays, assay validation and pharmacopoeial requirements. Emphasis is on interpreting dose–response curves, assay parallelism, stability and troubleshooting common errors in biological assays. The content fosters deeper understanding of how biological activity differs from chemical purity and why standardized reference material and proper sample handling are essential. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary purpose of performing a bioassay for ACTH?

  • To determine the peptide sequence of ACTH
  • To measure the biological potency or activity of an ACTH preparation
  • To quantify total protein content in a sample
  • To identify contaminants by chromatography

Correct Answer: To measure the biological potency or activity of an ACTH preparation

Q2. In bioassay terminology, what does ED50 represent?

  • The dose producing maximal response
  • The dose producing 50% of the maximal response
  • The dose that is lethal to 50% of subjects
  • The dose producing no observable effect

Correct Answer: The dose producing 50% of the maximal response

Q3. Which in vivo endpoint is commonly used to assess ACTH activity in rodent bioassays?

  • Reduction in blood glucose
  • Increase in adrenal cortical steroid secretion (e.g., corticosterone)
  • Change in heart rate
  • Alteration in body temperature

Correct Answer: Increase in adrenal cortical steroid secretion (e.g., corticosterone)

Q4. Which of the following is a typical in vitro bioassay model for ACTH activity?

  • Hepatocyte glucose production assay
  • Adrenal cortical cell culture measuring cAMP or cortisol output
  • Neuronal synapse formation assay
  • Platelet aggregation assay

Correct Answer: Adrenal cortical cell culture measuring cAMP or cortisol output

Q5. Why is a reference standard required in ACTH bioassays?

  • To act as a preservative in samples
  • To provide a benchmark for calculating relative potency and ensuring assay accuracy
  • To change the assay temperature
  • To sterilize cell cultures

Correct Answer: To provide a benchmark for calculating relative potency and ensuring assay accuracy

Q6. What is the typical shape of a dose–response curve for ACTH bioassays when plotted on a semilog scale?

  • Linear declining line
  • S-shaped (sigmoidal) curve
  • Parabolic curve
  • Exponential decay

Correct Answer: S-shaped (sigmoidal) curve

Q7. How is assay sensitivity defined in the context of ACTH bioassays?

  • The maximum possible response of the assay
  • The lowest concentration of ACTH that produces a measurable biological effect
  • The ability of the assay to measure chemical impurities
  • The speed at which the assay is completed

Correct Answer: The lowest concentration of ACTH that produces a measurable biological effect

Q8. Which unit is commonly used to express biological potency of ACTH preparations?

  • moles per liter (M)
  • International Units (IU) or units per mg relative to a reference standard
  • grams per liter (g/L)
  • Optical density units (OD)

Correct Answer: International Units (IU) or units per mg relative to a reference standard

Q9. What does parallelism between sample and standard dilution-response curves indicate?

  • The sample contains a different active principle than the standard
  • The sample behaves similarly to the standard and lacks significant matrix interference
  • The assay is invalid and must be discarded
  • The sample must be analyzed by chromatography instead

Correct Answer: The sample behaves similarly to the standard and lacks significant matrix interference

Q10. How is ED50 experimentally determined in a typical bioassay?

  • By measuring the highest dose only
  • From the dose–response curve as the dose corresponding to 50% of maximal response
  • By counting surviving animals at each dose
  • By measuring placebo response

Correct Answer: From the dose–response curve as the dose corresponding to 50% of maximal response

Q11. How is potency often expressed when comparing a test ACTH sample to a reference standard?

  • In percentage relative potency or IU per mg compared to the reference
  • As absolute molar concentration only
  • As the number of amino acids
  • As the retention time on HPLC

Correct Answer: In percentage relative potency or IU per mg compared to the reference

Q12. Which ethical consideration is most relevant when conducting in vivo ACTH bioassays?

  • Ensuring animals receive the highest possible dose
  • Minimizing animal use, suffering and applying the 3Rs (Replacement, Reduction, Refinement)
  • Using unvalidated test substances freely
  • Avoiding record keeping to save time

Correct Answer: Minimizing animal use, suffering and applying the 3Rs (Replacement, Reduction, Refinement)

Q13. What is a matrix effect in the context of ACTH bioassays?

  • An intended enhancement of assay signal by the standard
  • Interference from sample components that alter the assay response compared to the standard
  • A special buffer added to stabilize ACTH
  • A statistical method for calculating ED50

Correct Answer: Interference from sample components that alter the assay response compared to the standard

Q14. Which validation parameter assesses the closeness of measured values to the true value in ACTH bioassays?

  • Precision
  • Accuracy
  • Linearity
  • Specificity

Correct Answer: Accuracy

Q15. What is an appropriate storage practice for lyophilized ACTH reference standard to maintain activity?

  • Store at room temperature in direct sunlight
  • Store lyophilized at -20°C or colder and avoid repeated freeze–thaw cycles
  • Keep constantly at 37°C to preserve peptide conformation
  • Store dissolved in water at 4°C for months

Correct Answer: Store lyophilized at -20°C or colder and avoid repeated freeze–thaw cycles

Q16. Which substance class commonly interferes with peptide bioassays by degrading ACTH?

  • Proteases and peptidases
  • Neutral salts like NaCl
  • Non-ionic detergents at low concentrations
  • Vitamins

Correct Answer: Proteases and peptidases

Q17. What role do pharmacopoeias play in ACTH bioassays?

  • They ban all biological assays
  • They provide standardized reference materials, assay protocols and acceptance criteria
  • They only regulate small-molecule drugs, not peptides
  • They recommend informal laboratory practices without standards

Correct Answer: They provide standardized reference materials, assay protocols and acceptance criteria

Q18. Which practice improves reproducibility of ACTH bioassays?

  • Using different cell lines each run
  • Standardizing experimental conditions and using the same reference standard batch
  • Varying incubation times randomly
  • Mixing multiple standards without documentation

Correct Answer: Standardizing experimental conditions and using the same reference standard batch

Q19. How does an immunoassay (e.g., ELISA) differ from a biological bioassay for ACTH?

  • Immunoassay measures biological activity directly
  • Immunoassay measures immunoreactivity (antigenicity) and may not reflect true biological potency
  • Immunoassay always provides ED50 values
  • Immunoassay measures only contaminants

Correct Answer: Immunoassay measures immunoreactivity (antigenicity) and may not reflect true biological potency

Q20. Which statement best distinguishes biological activity from chemical purity?

  • Chemical purity guarantees biological activity
  • Biological activity indicates functional effect in a bioassay, while chemical purity describes the proportion of desired compound by chemical analysis
  • Both terms are identical and interchangeable
  • Purity is irrelevant for peptide drugs

Correct Answer: Biological activity indicates functional effect in a bioassay, while chemical purity describes the proportion of desired compound by chemical analysis

Q21. If an ACTH sample shows significantly lower potency than its label claim in bioassay, what is the most likely explanation?

  • Enhanced receptor sensitivity
  • Degradation or loss of biological activity due to improper storage/handling
  • Improved formulation efficacy
  • Measurement of chemical impurities only

Correct Answer: Degradation or loss of biological activity due to improper storage/handling

Q22. Which intracellular messenger is commonly measured as an early indicator of ACTH receptor activation in adrenal cells?

  • cAMP (cyclic adenosine monophosphate)
  • cGMP (cyclic guanosine monophosphate)
  • Calcium only
  • Nitric oxide

Correct Answer: cAMP (cyclic adenosine monophosphate)

Q23. In a dose–response experiment, a rightward shift of the sample curve relative to standard indicates:

  • Increased potency of the sample
  • Decreased potency of the sample (higher ED50)
  • No change in potency
  • Improved specificity

Correct Answer: Decreased potency of the sample (higher ED50)

Q24. A parallel line assay assumes which of the following about standard and sample responses?

  • They have identical maximal responses but different slopes
  • They have similar slopes and are parallel on a log-dose response scale
  • The standard is always inactive
  • They cross at multiple points

Correct Answer: They have similar slopes and are parallel on a log-dose response scale

Q25. Why must sterility and endotoxin be controlled when testing ACTH in cell-based bioassays?

  • Sterility is irrelevant for cell assays
  • Contaminants can affect cell viability and produce false assay results
  • Endotoxin increases ACTH potency reliably
  • Sterilization increases peptide concentration

Correct Answer: Contaminants can affect cell viability and produce false assay results

Q26. How does elevated temperature exposure affect ACTH peptides during storage?

  • Enhances long-term stability
  • Causes peptide denaturation and degradation, reducing biological activity
  • Converts ACTH into a more potent form
  • Has no effect on peptide integrity

Correct Answer: Causes peptide denaturation and degradation, reducing biological activity

Q27. What is the benefit of lyophilizing ACTH formulations for long-term storage?

  • Increases water activity to preserve microbes
  • Reduces hydrolytic degradation and improves stability during storage
  • Makes the peptide permanently inactive
  • Allows storage at high temperatures

Correct Answer: Reduces hydrolytic degradation and improves stability during storage

Q28. A synthetic ACTH analogue shows strong immunoreactivity but weak biological response in a bioassay. What does this indicate?

  • The analogue is more potent biologically
  • The analogue binds antibodies but has reduced receptor agonist activity
  • The bioassay is measuring the wrong endpoint
  • The standard is contaminated

Correct Answer: The analogue binds antibodies but has reduced receptor agonist activity

Q29. What does the limit of quantification (LOQ) in an ACTH bioassay describe?

  • The maximal dose that can be tested
  • The lowest concentration that can be measured with acceptable precision and accuracy
  • The concentration at which toxicity occurs
  • The dilution factor of the standard

Correct Answer: The lowest concentration that can be measured with acceptable precision and accuracy

Q30. When is an in vivo bioassay preferred over an in vitro test for assessing ACTH activity?

  • When receptor-level signaling is the only concern
  • When assessment of whole-organism responses, metabolism or systemic effects is required
  • When quick high-throughput screening is needed
  • When immunoreactivity alone is sufficient

Correct Answer: When assessment of whole-organism responses, metabolism or systemic effects is required

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