Cell signaling pathways MCQs With Answer

Cell signaling pathways MCQs With Answer

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Cell signaling pathways MCQs With Answer

Introduction: This quiz compilation on cell signaling pathways is designed for M.Pharm students studying Advanced Pharmaceutical Biotechnology. It covers key signaling mechanisms — including GPCR, RTK, JAK-STAT, MAPK, PI3K-Akt, Wnt, Notch, Hedgehog, TGF-β and ubiquitin-mediated regulation — with emphasis on molecular details, regulatory motifs, cross-talk and pharmacological targets. Each question tests conceptual understanding and applied knowledge relevant to drug discovery and therapeutic modulation of signaling. The format provides concise options and clear answers to reinforce learning and prepare students for exams or research discussions in translational pharmacology and targeted therapy design.

Q1. Which molecule acts as the primary second messenger produced by adenylate cyclase downstream of many GPCRs?

  • cAMP (cyclic AMP)
  • Diacylglycerol (DAG)
  • Inositol 1,4,5-trisphosphate (IP3)
  • Calcium ions (Ca2+)

Correct Answer: cAMP (cyclic AMP)

Q2. Activation of receptor tyrosine kinases (RTKs) primarily results in which enzymatic activity?

  • Serine/threonine kinase activity
  • Tyrosine kinase activity
  • Protein phosphatase activity
  • GTPase activity

Correct Answer: Tyrosine kinase activity

Q3. The SH2 domain present in many signaling proteins selectively binds to which motif on activated receptors?

  • Phosphotyrosine-containing motifs
  • Phosphoserine-containing motifs
  • Polyproline motifs
  • Methylated lysine residues

Correct Answer: Phosphotyrosine-containing motifs

Q4. Phosphoinositide 3-kinase (PI3K) phosphorylates which membrane lipid to generate a docking site for PH-domain proteins?

  • PIP (phosphatidylinositol monophosphate)
  • PIP2 (phosphatidylinositol 4,5-bisphosphate)
  • PIP3 (phosphatidylinositol 3,4,5-trisphosphate)
  • PI (phosphatidylinositol)

Correct Answer: PIP3 (phosphatidylinositol 3,4,5-trisphosphate)

Q5. Ras activation at the plasma membrane is accelerated by exchange factors such as SOS; SOS acts as which type of regulatory protein?

  • GTPase-activating protein (GAP)
  • Guanine nucleotide exchange factor (GEF)
  • Protein kinase
  • Protein phosphatase

Correct Answer: Guanine nucleotide exchange factor (GEF)

Q6. In the JAK-STAT signaling pathway, activated STAT proteins primarily function as which of the following?

  • Ion channels
  • Scaffold proteins
  • Transcription factors
  • Ubiquitin ligases

Correct Answer: Transcription factors

Q7. What is the canonical order of kinase activation in the classical MAPK/ERK cascade?

  • MEK → RAF → ERK
  • ERK → MEK → RAF
  • RAF → MEK → ERK
  • PI3K → AKT → mTOR

Correct Answer: RAF → MEK → ERK

Q8. Prolonged exposure to an agonist that leads to reduced responsiveness of the receptor is termed:

  • Upregulation
  • Desensitization
  • Sensitization
  • Signal amplification

Correct Answer: Desensitization

Q9. Beta-arrestin proteins contribute to GPCR regulation primarily by:

  • Acting as GEFs for G proteins
  • Mediating GPCR desensitization and receptor internalization
  • Generating cAMP second messenger
  • Directly phosphorylating receptors

Correct Answer: Mediating GPCR desensitization and receptor internalization

Q10. Activation of the PI3K-Akt pathway promotes cell survival primarily through which mechanism?

  • Activation of executioner caspases
  • Phosphorylation and inactivation of pro-apoptotic proteins (e.g., Bad)
  • Release of cytochrome c from mitochondria
  • Induction of DNA fragmentation

Correct Answer: Phosphorylation and inactivation of pro-apoptotic proteins (e.g., Bad)

Q11. Notch signaling transduces a signal across the membrane by which unique mechanism?

  • Generation of cAMP second messenger
  • Proteolytic cleavage releasing the Notch intracellular domain (NICD)
  • Activation of heterotrimeric G proteins
  • Formation of receptor tyrosine kinase dimers

Correct Answer: Proteolytic cleavage releasing the Notch intracellular domain (NICD)

Q12. In the canonical Wnt/β-catenin pathway, Wnt binding leads to which key intracellular event?

  • Increased β-catenin degradation by the proteasome
  • Stabilization of β-catenin and activation of TCF/LEF-dependent transcription
  • Activation of heterotrimeric G proteins to raise cAMP
  • Rapid ubiquitination of β-catenin and lysosomal targeting

Correct Answer: Stabilization of β-catenin and activation of TCF/LEF-dependent transcription

Q13. In Hedgehog signaling, which transmembrane protein acts as the principal signal transducer once Patched inhibition is relieved?

  • Patched (PTCH)
  • Smoothened (SMO)
  • Gli transcription factor
  • Sonic hedgehog ligand (SHH)

Correct Answer: Smoothened (SMO)

Q14. TGF-β family signaling is mediated through receptors with which intrinsic enzymatic activity and downstream effectors?

  • Tyrosine kinase receptors and STATs
  • Serine/threonine kinase receptors and Smad proteins
  • G-protein-coupled receptors and cAMP
  • Ion channel receptors and calcium-dependent kinases

Correct Answer: Serine/threonine kinase receptors and Smad proteins

Q15. Which form of polyubiquitination classically targets proteins for proteasomal degradation?

  • K63-linked polyubiquitination
  • K48-linked polyubiquitination
  • Monoubiquitination
  • SUMOylation

Correct Answer: K48-linked polyubiquitination

Q16. Imatinib is a prototype targeted drug that inhibits which kinase relevant in chronic myeloid leukemia?

  • EGFR tyrosine kinase
  • BCR-ABL tyrosine kinase
  • mTOR serine/threonine kinase
  • JAK family kinases

Correct Answer: BCR-ABL tyrosine kinase

Q17. Biased agonism at G protein-coupled receptors refers to:

  • A ligand that irreversibly binds and inactivates the receptor
  • A ligand that preferentially activates specific downstream pathways by stabilizing distinct receptor conformations
  • A ligand that only competes with endogenous agonists without efficacy
  • A ligand that exclusively promotes receptor degradation

Correct Answer: A ligand that preferentially activates specific downstream pathways by stabilizing distinct receptor conformations

Q18. Scaffold proteins in signaling cascades (for example KSR in MAPK signaling) primarily serve to:

  • Tag kinases for degradation
  • Enhance specificity and efficiency by assembling pathway components
  • Directly phosphorylate transcription factors
  • Serve as membrane ion channels

Correct Answer: Enhance specificity and efficiency by assembling pathway components

Q19. NF-κB is normally held inactive in the cytoplasm by which inhibitory protein that must be degraded for NF-κB activation?

  • IκB
  • p53
  • CREB
  • Akt

Correct Answer: IκB

Q20. Which technique provides real-time, label-free measurement of receptor-ligand binding kinetics widely used in signaling studies?

  • Western blotting
  • ELISA (enzyme-linked immunosorbent assay)
  • Surface plasmon resonance (SPR)
  • Mass spectrometry

Correct Answer: Surface plasmon resonance (SPR)

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