Principles of cell communication MCQs With Answer

Principles of cell communication MCQs With Answer

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Principles of cell communication MCQs With Answer offers B.Pharm students a focused review of how cells send, receive, and process signals relevant to drug action. This introduction covers core concepts such as cell signaling types, signal transduction pathways, receptors (GPCRs, RTKs, ion channels), second messengers (cAMP, IP3, Ca2+), amplification, specificity, desensitization, and pharmacological modulation. Emphasis is placed on molecular mechanisms, clinical relevance, and typical drug targets to prepare you for exams and therapeutics. Clear, targeted MCQs with answers help consolidate mechanisms and identify key drug–receptor relationships. ‘Now let’s test your knowledge with 30 MCQs on this topic.’

Q1. What is the primary role of cell signaling in multicellular organisms?

  • To generate energy for cells
  • To enable cells to communicate and coordinate functions
  • To replicate DNA
  • To synthesize lipids exclusively

Correct Answer: To enable cells to communicate and coordinate functions

Q2. Which of the following is NOT a typical mode of intercellular signaling?

  • Endocrine signaling
  • Paracrine signaling
  • Autocrine signaling
  • Fragmentary signaling

Correct Answer: Fragmentary signaling

Q3. G-protein coupled receptors (GPCRs) primarily transduce signals through which intermediates?

  • Second messengers like cAMP and IP3
  • Direct DNA binding
  • Phospholipid bilayer flipping
  • Microtubule assembly

Correct Answer: Second messengers like cAMP and IP3

Q4. Which second messenger is directly produced by adenylyl cyclase activity?

  • Inositol trisphosphate (IP3)
  • Diacylglycerol (DAG)
  • cAMP
  • cGMP

Correct Answer: cAMP

Q5. Activation of phospholipase C (PLC) typically yields which pair of second messengers?

  • cAMP and cGMP
  • IP3 and DAG
  • Ca2+ and ATP
  • NO and CO

Correct Answer: IP3 and DAG

Q6. Which receptor class has intrinsic tyrosine kinase activity important for growth factor signaling?

  • Ligand-gated ion channels
  • Receptor tyrosine kinases (RTKs)
  • GPCRs
  • Intracellular steroid receptors

Correct Answer: Receptor tyrosine kinases (RTKs)

Q7. What is signal amplification in the context of cell communication?

  • The process by which a single ligand reduces receptor number
  • The cascade where one activated receptor leads to production of many second messenger molecules
  • Degradation of signaling proteins to terminate signal
  • Transport of signals across the nuclear membrane

Correct Answer: The cascade where one activated receptor leads to production of many second messenger molecules

Q8. Which molecule is a common intracellular calcium mobilizer released from the endoplasmic reticulum?

  • cAMP
  • IP3
  • DAG
  • ATP synthase

Correct Answer: IP3

Q9. Beta-adrenergic receptors are classic examples of which receptor family?

  • Receptor tyrosine kinases
  • G-protein coupled receptors
  • Ligand-gated ion channels
  • Nuclear hormone receptors

Correct Answer: G-protein coupled receptors

Q10. Which process decreases receptor responsiveness following prolonged exposure to agonist?

  • Up-regulation
  • Desensitization (tachyphylaxis)
  • Translocation to nucleus
  • Synthetic activation

Correct Answer: Desensitization (tachyphylaxis)

Q11. The JAK-STAT pathway is primarily associated with signaling for which class of ligands?

  • Neurotransmitters like GABA
  • Cytokines and growth factors
  • Lipid hormones like prostaglandins
  • Small gaseous transmitters like NO

Correct Answer: Cytokines and growth factors

Q12. Which signaling molecule freely diffuses through membranes to act on intracellular targets and is a vasodilator produced by endothelial cells?

  • cAMP
  • Nitric oxide (NO)
  • DAG
  • IP3

Correct Answer: Nitric oxide (NO)

Q13. Which intracellular domain modification is commonly used by RTKs to recruit downstream signaling proteins?

  • Methylation of arginine residues
  • Phosphorylation of tyrosine residues
  • Glycosylation of serine residues
  • Acetylation of lysine residues

Correct Answer: Phosphorylation of tyrosine residues

Q14. Scaffold proteins in signaling pathways primarily function to:

  • Hydrolyze second messengers
  • Bring pathway components into close proximity for specificity
  • Transport ligands across membranes
  • Directly phosphorylate receptors

Correct Answer: Bring pathway components into close proximity for specificity

Q15. Which type of receptor directly controls ion flux in milliseconds upon ligand binding?

  • G-protein coupled receptors
  • Receptor tyrosine kinases
  • Ligand-gated ion channels (ionotropic receptors)
  • Nuclear receptors

Correct Answer: Ligand-gated ion channels (ionotropic receptors)

Q16. Which second messenger activates protein kinase A (PKA)?

  • cGMP
  • cAMP
  • IP3
  • DAG

Correct Answer: cAMP

Q17. Pertussis toxin exerts its effect by ADP-ribosylating which signaling component?

  • Receptor tyrosine kinases
  • Gαi protein of heterotrimeric G-proteins
  • Adenylyl cyclase catalytic site
  • Protein kinase C

Correct Answer: Gαi protein of heterotrimeric G-proteins

Q18. Which mechanism allows a single ligand to produce different responses in different target cells?

  • Universal receptor expression
  • Differences in receptor type and downstream signaling machinery
  • Ligand degradation rate only
  • Identical second messenger levels in all cells

Correct Answer: Differences in receptor type and downstream signaling machinery

Q19. Receptor down-regulation commonly involves which cellular process?

  • Endocytosis and lysosomal degradation of receptors
  • Direct receptor phosphorylation in the nucleus
  • Immediate increase in receptor gene transcription
  • Mitochondrial import of receptors

Correct Answer: Endocytosis and lysosomal degradation of receptors

Q20. Which pathway is central to many growth factor signals and involves a kinase cascade from RAF to MEK to ERK?

  • PI3K-AKT pathway
  • MAPK/ERK pathway
  • cGMP-PKG pathway
  • NF-κB canonical pathway

Correct Answer: MAPK/ERK pathway

Q21. In signal transduction, ‘cross-talk’ refers to:

  • Physical contact between receptors
  • Interactions and modulation between distinct signaling pathways
  • Complete isolation of cellular pathways
  • Only hormonal signaling between organs

Correct Answer: Interactions and modulation between distinct signaling pathways

Q22. Which drug action illustrates competitive antagonism at a receptor?

  • A drug that irreversibly inactivates the receptor enzyme
  • A reversible antagonist that shifts agonist dose–response curve to the right
  • A drug that increases receptor number
  • A drug that activates an alternate pathway

Correct Answer: A reversible antagonist that shifts agonist dose–response curve to the right

Q23. Nuclear receptors often regulate gene expression by:

  • Opening ion channels
  • Acting as ligand-activated transcription factors
  • Activating adenylate cyclase at the membrane
  • Generating IP3 from membrane lipids

Correct Answer: Acting as ligand-activated transcription factors

Q24. Which enzyme degrades cAMP to terminate its signaling?

  • Phosphodiesterase (PDE)
  • Adenylyl cyclase
  • Protein kinase A
  • Nitric oxide synthase

Correct Answer: Phosphodiesterase (PDE)

Q25. Agonist affinity and intrinsic efficacy together determine:

  • Drug solubility only
  • Potency and maximal response (efficacy) of a drug
  • The antigenicity of a protein
  • Molecular weight of the receptor

Correct Answer: Potency and maximal response (efficacy) of a drug

Q26. Which molecule commonly serves as a lipid-derived second messenger that activates protein kinase C (PKC)?

  • cAMP
  • DAG (diacylglycerol)
  • IP3
  • ATP

Correct Answer: DAG (diacylglycerol)

Q27. Autocrine signaling is best defined as:

  • Signaling where hormones travel through blood to distant targets
  • When a cell responds to signaling molecules that it secretes itself
  • Neuronal signaling across synapses
  • Cell signaling that only occurs during embryogenesis

Correct Answer: When a cell responds to signaling molecules that it secretes itself

Q28. Which characteristic makes GPCRs attractive drug targets?

  • They are located exclusively in the nucleus
  • They modulate a wide range of physiological processes and are accessible at the cell surface
  • They do not interact with G proteins
  • They cannot be regulated by desensitization

Correct Answer: They modulate a wide range of physiological processes and are accessible at the cell surface

Q29. Which event directly follows ligand binding to a receptor tyrosine kinase?

  • Receptor dimerization and trans-autophosphorylation
  • Immediate opening of a pore for ions
  • Export of the receptor to the extracellular matrix
  • Conversion of receptor into a transcription factor without modification

Correct Answer: Receptor dimerization and trans-autophosphorylation

Q30. A pharmacological antagonist that reduces the maximal response of an agonist, even at high agonist concentrations, is termed:

  • A competitive antagonist
  • An inverse agonist
  • A noncompetitive antagonist (irreversible or allosteric)
  • A partial agonist

Correct Answer: A noncompetitive antagonist (irreversible or allosteric)

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