Receptors MCQs With Answer

Receptors MCQs With Answer are essential study tools for B. Pharm students to master pharmacodynamics and drug action. This concise introduction highlights receptor classification, signaling mechanisms, ligand binding, dose–response relationships, receptor regulation, and therapeutic implications. Focused practice with targeted questions on GPCRs, ion channels, enzyme-linked receptors, nuclear receptors, agonists, antagonists, allosteric modulators, and receptor kinetics improves exam readiness and clinical understanding. Questions emphasize key terms like KD, Bmax, spare receptors, desensitization, biased agonism, and competitive versus noncompetitive antagonism. Clear explanations reinforce drug design principles and safety considerations. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which receptor family mainly signals through G proteins to activate downstream effectors?

• Ion channel receptors
• G protein-coupled receptors (GPCRs)
• Receptor tyrosine kinases
• Nuclear receptors

Correct Answer: G protein-coupled receptors (GPCRs)

Q2. Which parameter represents the total number of binding sites in a tissue sample during radioligand binding?

• Kd
• Bmax
• Koff
• EC50

Correct Answer: Bmax

Q3. A drug that binds to a receptor and produces a maximal response is called:

• Partial agonist
• Inverse agonist
• Full agonist
• Neutral antagonist

Correct Answer: Full agonist

Q4. Competitive antagonism is characterized pharmacologically by which effect on the dose–response curve?

• Decrease in Emax with no change in EC50
• Rightward shift of the curve with no change in Emax
• Leftward shift of the curve
• Decrease in both EC50 and Emax

Correct Answer: Rightward shift of the curve with no change in Emax

Q5. Which receptor type directly allows ion flux across the membrane when activated?

• G protein-coupled receptors
• Ligand-gated ion channels
• Enzyme-linked receptors
• Intracellular steroid receptors

Correct Answer: Ligand-gated ion channels

Q6. KD in receptor pharmacology indicates:

• Maximum effect produced by a ligand
• Affinity of ligand for receptor
• Rate of receptor internalization
• Concentration producing 50% of maximal effect

Correct Answer: Affinity of ligand for receptor

Q7. Which is an example of a receptor tyrosine kinase?

• β2 adrenergic receptor
• Insulin receptor
• Nicotinic acetylcholine receptor
• Glucocorticoid receptor

Correct Answer: Insulin receptor

Q8. Inverse agonists produce which of the following effects at constitutively active receptors?

• No effect on basal activity
• Increase receptor activity above basal level
• Reduce constitutive activity below basal level
• Block agonist binding without changing activity

Correct Answer: Reduce constitutive activity below basal level

Q9. Spare receptors refer to:

• Receptors that are permanently inactive
• Excess receptors such that maximal response occurs without full occupancy
• Receptors only present in embryonic tissues
• Receptors that cannot be downregulated

Correct Answer: Excess receptors such that maximal response occurs without full occupancy

Q10. Which technique is commonly used to determine KD and Bmax?

• Western blotting
• Radioligand binding assay
• ELISA for cytokines
• Mass spectrometry of metabolites

Correct Answer: Radioligand binding assay

Q11. A partial agonist at a receptor will:

• Produce a greater response than a full agonist
• Produce a lower maximal response than a full agonist even at full occupancy
• Have no intrinsic activity
• Always act as an antagonist in all tissues

Correct Answer: Produce a lower maximal response than a full agonist even at full occupancy

Q12. Noncompetitive antagonists often reduce the agonist response by:

• Competing for the same orthosteric binding site
• Irreversibly blocking or allosterically modulating receptor function
• Increasing agonist concentration
• Enhancing receptor coupling to G proteins

Correct Answer: Irreversibly blocking or allosterically modulating receptor function

Q13. Functional selectivity (biased agonism) means a ligand:

• Activates all signaling pathways equally
• Selectively stabilizes receptor conformations that favor certain signaling pathways
• Is always a full agonist in every tissue
• Cannot bind receptors at physiological concentrations

Correct Answer: Selectively stabilizes receptor conformations that favor certain signaling pathways

Q14. The Schild plot is used to quantify which pharmacological property?

• Intrinsic activity of an agonist
• Type and potency of a competitive antagonist (pA2)
• Maximum binding capacity Bmax
• Rate of receptor internalization

Correct Answer: Type and potency of a competitive antagonist (pA2)

Q15. Which receptor class typically acts by altering gene transcription after ligand binding?

• Nuclear receptors (e.g., steroid receptors)
• Ionotropic glutamate receptors
• GPCRs coupled to Gs
• Receptor tyrosine kinases acting only at membrane

Correct Answer: Nuclear receptors (e.g., steroid receptors)

Q16. Tachyphylaxis refers to:

• Long-term upregulation of receptors over months
• Rapid decrease in response to repeated drug exposure
• Enhanced response to a drug after repeated dosing
• Allergic reaction to a receptor ligand

Correct Answer: Rapid decrease in response to repeated drug exposure

Q17. Which of the following is a ligand-gated ion channel involved in fast synaptic transmission?

• Muscarinic M2 receptor
• Nicotinic acetylcholine receptor
• β2 adrenergic receptor
• Tyrosine kinase receptor

Correct Answer: Nicotinic acetylcholine receptor

Q18. Allosteric modulators act by:

• Binding to the orthosteric site and competing with agonists
• Binding to a distinct site and altering receptor response to the orthosteric ligand
• Blocking receptor synthesis
• Changing the agonist’s chemical structure

Correct Answer: Binding to a distinct site and altering receptor response to the orthosteric ligand

Q19. Which measure indicates the potency of a drug in producing a specified effect?

• Bmax
• KD
• EC50
• Koff

Correct Answer: EC50

Q20. Desensitization of GPCRs often involves:

• Phosphorylation by GRKs and arrestin binding
• Increased receptor synthesis
• Immediate degradation of ligand
• Permanent inactivation of downstream enzymes

Correct Answer: Phosphorylation by GRKs and arrestin binding

Q21. The Scatchard plot is used to evaluate:

• Gene expression changes after receptor activation
• Ligand binding affinity and receptor number
• Clinical side effects of drugs
• Enzyme kinetics for metabolic pathways

Correct Answer: Ligand binding affinity and receptor number

Q22. Which receptor antagonist would likely be reversible if it binds noncovalently at the orthosteric site?

• Irreversible antagonist
• Noncompetitive antagonist
• Competitive reversible antagonist
• Suicide inhibitor

Correct Answer: Competitive reversible antagonist

Q23. Biased agonists are potentially beneficial because they:

• Eliminate all adverse effects by binding weaker
• Selectively activate therapeutic pathways while avoiding adverse signaling
• Always give greater efficacy than full agonists
• Prevent receptor internalization entirely

Correct Answer: Selectively activate therapeutic pathways while avoiding adverse signaling

Q24. Which statement about agonist efficacy is correct?

• Efficacy equals affinity
• High affinity always means high efficacy
• Efficacy is the ability to produce a response after binding
• Efficacy is measured by Kd

Correct Answer: Efficacy is the ability to produce a response after binding

Q25. The nicotinic receptor at the neuromuscular junction is best classified as:

• Metabotropic receptor
• Ligand-gated ion channel that is cation selective
• Receptor tyrosine kinase
• Nuclear receptor

Correct Answer: Ligand-gated ion channel that is cation selective

Q26. A drug with a lower Kd compared to another has:

• Lower affinity for the receptor
• Higher affinity for the receptor
• Faster dissociation rate only
• No binding at physiological concentrations

Correct Answer: Higher affinity for the receptor

Q27. Which receptor type commonly signals via JAK-STAT pathway?

• Receptor tyrosine kinase
• Cytokine receptors (non-tyrosine kinase-associated)
• GPCRs
• Ionotropic GABA receptors

Correct Answer: Cytokine receptors (non-tyrosine kinase-associated)

Q28. Which of the following best describes a neutral antagonist?

• Produces opposite effect to an agonist
• Blocks agonist activity without affecting basal receptor activity
• Activates receptor to produce partial response
• Irreversibly inhibits receptor function

Correct Answer: Blocks agonist activity without affecting basal receptor activity

Q29. Receptor upregulation commonly occurs after:

• Chronic agonist exposure
• Chronic antagonist exposure or receptor blockade
• Single high dose of agonist
• Complete absence of ligand only in vitro

Correct Answer: Chronic antagonist exposure or receptor blockade

Q30. Which parameter describes the dissociation rate of a ligand from its receptor?

• Kon
• Koff
• EC50
• Bmax

Correct Answer: Koff

Q31. The EC50 is affected by receptor number when there are:

• No spare receptors
• Spare receptors present
• Only irreversible antagonists present
• Ligand is an inverse agonist

Correct Answer: Spare receptors present

Q32. Which neurotransmitter acts on both GPCRs and ligand-gated ion channels?

• Dopamine only via GPCRs
• Glutamate only via ion channels
• Acetylcholine acting at muscarinic (GPCR) and nicotinic (ion channel) receptors
• Insulin acting on RTKs

Correct Answer: Acetylcholine acting at muscarinic (GPCR) and nicotinic (ion channel) receptors

Q33. A drug that reduces the efficacy of an agonist but cannot be overcome by increasing agonist concentration is likely:

• Competitive antagonist
• Partial agonist
• Noncompetitive antagonist
• Inverse agonist only

Correct Answer: Noncompetitive antagonist

Q34. Which of the following receptors is an intracellular transcription factor activated by lipophilic ligands?

• β-adrenergic receptor
• Glucocorticoid receptor
• Nicotinic receptor
• Trk receptor

Correct Answer: Glucocorticoid receptor

Q35. Ki is most closely associated with which concept?

• Intrinsic efficacy of an agonist
• Equilibrium inhibition constant for an antagonist binding
• Maximal receptor number
• Rate of G protein activation

Correct Answer: Equilibrium inhibition constant for an antagonist binding

Q36. Receptor desensitization that occurs within minutes and often involves phosphorylation is termed:

• Downregulation
• Homologous or heterologous desensitization
• Tachyphylaxis through gene deletion
• Permanent receptor loss

Correct Answer: Homologous or heterologous desensitization

Q37. Which receptor family uses cyclic AMP (cAMP) as a common second messenger through Gs coupling?

• Ionotropic GABA receptors
• Gs-coupled GPCRs such as β-adrenergic receptors
• Toll-like receptors
• Nuclear thyroid hormone receptors

Correct Answer: Gs-coupled GPCRs such as β-adrenergic receptors

Q38. The phenomenon where different tissues show different maximal responses to the same agonist is due to:

• Variations in receptor number and coupling efficiency
• Inconstant chemical structure of the agonist
• Equal receptor reserve in all tissues
• Identical downstream signaling in all cells

Correct Answer: Variations in receptor number and coupling efficiency

Q39. Which is a common downstream effect of receptor tyrosine kinase activation?

• Immediate opening of chloride channels
• Phosphorylation cascades involving MAPK/ERK pathways
• Direct activation of adenylyl cyclase by G proteins
• Release of intracellular calcium via IP3 exclusively

Correct Answer: Phosphorylation cascades involving MAPK/ERK pathways

Q40. A drug that binds equally to all receptor conformations but prevents activation is best described as:

• Full agonist
• Neutral antagonist
• Inverse agonist
• Allosteric enhancer

Correct Answer: Neutral antagonist

Q41. Which statement correctly describes pharmacodynamic tolerance related to receptors?

• Tolerance always involves increased drug metabolism only
• Tolerance can result from receptor downregulation or desensitization
• Tolerance is unrelated to receptor number or function
• Tolerance cannot be reversed

Correct Answer: Tolerance can result from receptor downregulation or desensitization

Q42. Which is an example of an allosteric potentiator?

• Benzodiazepines enhancing GABA-A receptor function
• Propranolol blocking β-adrenergic receptors
• Atropine blocking muscarinic receptors
• Gabapentin acting as a competitive antagonist

Correct Answer: Benzodiazepines enhancing GABA-A receptor function

Q43. Ligand efficacy is determined by:

• Only the ligand’s binding affinity
• Its ability to stabilize active receptor conformations leading to response
• The concentration of unrelated enzymes
• Number of mitochondria in the cell

Correct Answer: Its ability to stabilize active receptor conformations leading to response

Q44. Which receptor is primarily involved in fast excitatory neurotransmission in the CNS?

• GABA-A receptor
• NMDA and AMPA glutamate receptors
• Muscarinic M2 receptor
• β1 adrenergic receptor

Correct Answer: NMDA and AMPA glutamate receptors

Q45. An antagonist with high affinity but zero intrinsic activity will have which effect on agonist potency?

• Decrease agonist potency by shifting dose–response right
• Increase agonist potency
• Increase Emax without shifting curve
• No effect on agonist dose–response

Correct Answer: Decrease agonist potency by shifting dose–response right

Q46. Receptor oligomerization (e.g., GPCR dimers) can influence:

• Ligand binding, signaling specificity, and pharmacology
• Only gene transcription in the nucleus
• Only the metabolism of the ligand by liver enzymes
• Color of the cell membrane

Correct Answer: Ligand binding, signaling specificity, and pharmacology

Q47. Which experimental approach helps distinguish between competitive and noncompetitive antagonism?

• Measuring receptor mRNA levels only
• Performing concentration–response curves with increasing antagonist and observing Emax changes
• Measuring blood pressure alone
• Conducting ELISA for receptor protein

Correct Answer: Performing concentration–response curves with increasing antagonist and observing Emax changes

Q48. A drug that binds irreversibly to the active site of an enzyme-linked receptor is likely to act as:

• Reversible agonist
• Irreversible antagonist or inhibitor
• Neutral antagonist only
• Allosteric potentiator

Correct Answer: Irreversible antagonist or inhibitor

Q49. Which factor does NOT directly affect receptor–ligand binding affinity?

• Temperature and pH
• Ligand structure and charge
• Receptor conformation
• Color of the ligand solution

Correct Answer: Color of the ligand solution

Q50. In drug discovery, targeting receptors with tissue-selective expression is advantageous because it:

• Increases systemic side effects
• May improve therapeutic index by limiting off-target effects
• Prevents any need for dose optimization
• Makes drugs ineffective

Correct Answer: May improve therapeutic index by limiting off-target effects

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

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