Cell junctions and their functions MCQs With Answer

Cell junctions and their functions MCQs With Answer

Cell junctions are specialized structures—tight junctions, adherens junctions, desmosomes, gap junctions and hemidesmosomes—that maintain epithelial integrity, mediate intercellular communication and control paracellular permeability. Understanding molecular components (claudins, occludin, cadherins, catenins, connexins, integrins) and their roles in tissue mechanics, barrier function, signal transduction and disease is essential for B. Pharm students studying drug delivery, blood–brain barrier permeability, toxicology and pharmacotherapy. This topic links basic cell biology to pharmacological modulation of junctions, measurement techniques (TEER, freeze-fracture EM) and clinical consequences like pemphigus or cardiac arrhythmias. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which primary function best describes tight junctions in epithelial layers?

• Prevent paracellular diffusion and regulate barrier permeability
• Anchor cells mechanically to the extracellular matrix
• Allow rapid electrical conduction between cells
• Mediate endocytosis of membrane receptors

Correct Answer: Prevent paracellular diffusion and regulate barrier permeability

Q2. Which transmembrane proteins are central components of tight junction strands?

• Claudins and occludin
• Cadherins and catenins
• Connexins and pannexins
• Integrins and fibronectin

Correct Answer: Claudins and occludin

Q3. Which scaffold protein links tight junction transmembrane proteins to the actin cytoskeleton?

• ZO-1 (zonula occludens-1)
• Beta-catenin
• Desmoplakin
• Vinculin

Correct Answer: ZO-1 (zonula occludens-1)

Q4. The main transmembrane adhesion molecule in adherens junctions is:

• E-cadherin
• Desmoglein
• Occludin
• Connexin43

Correct Answer: E-cadherin

Q5. Desmosomal adhesion is mediated primarily by which molecules?

• Desmogleins and desmocollins
• Claudins and occludin
• Cadherins and integrins
• Connexins and pannexins

Correct Answer: Desmogleins and desmocollins

Q6. Hemidesmosomes connect epithelial cells to the basement membrane through which integrin?

• Alpha6beta4 integrin
• Alpha5beta1 integrin
• AlphaVbeta3 integrin
• Beta2 integrin

Correct Answer: Alpha6beta4 integrin

Q7. How many connexin subunits assemble to form a single connexon (hemichannel)?

• Six connexin subunits
• Three connexin subunits
• Eight connexin subunits
• Four connexin subunits

Correct Answer: Six connexin subunits

Q8. What is the principal function of gap junctions in tissues?

• Direct cytoplasmic exchange of ions and small signaling molecules between adjacent cells
• Prevent paracellular leakage of solutes
• Anchor cells to the extracellular matrix
• Initiate endocytosis of neighboring cell membranes

Correct Answer: Direct cytoplasmic exchange of ions and small signaling molecules between adjacent cells

Q9. Tight junctions contribute critically to the function of the blood–brain barrier by:

• Maintaining selective permeability and restricting paracellular flux
• Promoting leukocyte transmigration
• Generating action potentials in endothelial cells
• Facilitating bulk transcytosis of plasma proteins

Correct Answer: Maintaining selective permeability and restricting paracellular flux

Q10. Which experimental measurement is widely used to assess epithelial tight junction integrity in vitro?

• Transepithelial electrical resistance (TEER)
• Western blot for actin
• ELISA for albumin
• Optical density at 600 nm

Correct Answer: Transepithelial electrical resistance (TEER)

Q11. Which pro-inflammatory cytokine is known to increase tight junction permeability in epithelia?

• TNF-alpha
• Insulin
• Erythropoietin
• Prolactin

Correct Answer: TNF-alpha

Q12. Loss or downregulation of E-cadherin in epithelial tumors commonly promotes:

• Enhanced metastasis via epithelial–mesenchymal transition (EMT)
• Increased tight junction sealing
• Higher gap junction intercellular communication
• Stronger hemidesmosome attachment

Correct Answer: Enhanced metastasis via epithelial–mesenchymal transition (EMT)

Q13. Which protein links cadherins to the actin cytoskeleton at adherens junctions?

• Beta-catenin
• Desmoplakin
• ZO-1
• Connexin26

Correct Answer: Beta-catenin

Q14. Mutations in connexin 26 (GJB2) in humans most commonly cause:

• Non-syndromic sensorineural deafness
• Type II diabetes
• Hypertrophic cardiomyopathy
• Multiple sclerosis

Correct Answer: Non-syndromic sensorineural deafness

Q15. Autoantibodies directed against desmoglein result in which clinical condition?

• Pemphigus vulgaris
• Celiac disease
• Graves’ disease
• Rheumatoid arthritis

Correct Answer: Pemphigus vulgaris

Q16. How do tight junctions influence oral drug absorption?

• They limit paracellular drug absorption, affecting bioavailability of hydrophilic drugs
• They actively transport drugs into enterocytes
• They facilitate endocytosis of lipophilic drugs
• They enzymatically degrade peptide drugs

Correct Answer: They limit paracellular drug absorption, affecting bioavailability of hydrophilic drugs

Q17. Which junctional structure provides strong mechanical coupling in cardiac intercalated discs?

• Desmosomes
• Tight junctions
• Hemidesmosomes
• Clathrin-coated pits

Correct Answer: Desmosomes

Q18. The transmembrane protein occludin primarily contributes to tight junctions by:

• Regulating barrier permeability and junctional signaling
• Binding intermediate filaments directly
• Forming gap junction channels
• Degrading extracellular matrix proteins

Correct Answer: Regulating barrier permeability and junctional signaling

Q19. Hemidesmosomes link the intracellular intermediate filament network to the basement membrane via which cytoskeletal element?

• Intermediate filaments (keratin)
• Actin microfilaments
• Microtubules
• Microvilli

Correct Answer: Intermediate filaments (keratin)

Q20. Adherens junctions predominantly connect which cytoskeletal element between adjacent cells?

• Actin filaments
• Microtubules
• Intermediate filaments
• Extracellular collagen fibers

Correct Answer: Actin filaments

Q21. Which compound is commonly used experimentally to open tight junctions by chelating calcium and altering junction stability?

• EDTA (ethylenediaminetetraacetic acid)
• Glucose
• Albumin
• DMSO

Correct Answer: EDTA (ethylenediaminetetraacetic acid)

Q22. Which family of proteins is the primary structural component of classical gap junction channels?

• Connexins
• Cadherins
• Claudins
• Integrins

Correct Answer: Connexins

Q23. Cadherin-mediated adhesion is dependent on which ion for proper conformation and binding?

• Calcium (Ca2+)
• Sodium (Na+)
• Potassium (K+)
• Magnesium (Mg2+)

Correct Answer: Calcium (Ca2+)

Q24. ZO proteins (zonula occludens) primarily function to:

• Scaffold tight junction transmembrane proteins to the actin cytoskeleton
• Form the extracellular matrix
• Assemble desmosomal cadherins
• Drive vesicular trafficking across epithelia

Correct Answer: Scaffold tight junction transmembrane proteins to the actin cytoskeleton

Q25. Which microscopy technique best reveals the ultrastructural strands of tight junctions?

• Freeze-fracture electron microscopy
• Confocal fluorescence microscopy
• Scanning electron microscopy of whole cells
• Phase-contrast light microscopy

Correct Answer: Freeze-fracture electron microscopy

Q26. Which of the following is too large to pass through typical gap junction channels?

• Albumin (≈66 kDa)
• Cyclic AMP (cAMP)
• Calcium ions
• Inositol trisphosphate (IP3)

Correct Answer: Albumin (≈66 kDa)

Q27. The apical clustering of tight junctions, adherens junctions and desmosomes in epithelial cells is known as the:

• Apical junctional complex (terminal bar)
• Basal lamina
• Lateral membrane domain
• Golgi ribbon

Correct Answer: Apical junctional complex (terminal bar)

Q28. Mutations in desmosomal proteins such as desmoplakin are associated with which cardiac disorder?

• Arrhythmogenic right ventricular cardiomyopathy (ARVC)
• Long QT syndrome
• Mitral valve prolapse
• Hypertensive heart disease

Correct Answer: Arrhythmogenic right ventricular cardiomyopathy (ARVC)

Q29. Different claudin proteins in tight junctions mainly determine which property of the paracellular pathway?

• Ion selectivity and charge-dependent permeability
• Rate of endocytosis
• ATP production
• Protein synthesis

Correct Answer: Ion selectivity and charge-dependent permeability

Q30. Pharmacological blockade of gap junctions in cardiac tissue is most likely to cause which immediate physiological effect?

• Slowed electrical conduction and increased risk of arrhythmia
• Enhanced paracellular drug absorption
• Increased tight junction sealing
• Improved oxygen delivery to myocytes

Correct Answer: Slowed electrical conduction and increased risk of arrhythmia

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.

Mail- Sachin@pharmacyfreak.com