- Physical attachment of cells in a tissue or organ is mediated by different types of junctions, one of which is anchoring junctions. This includes both cell-cell adhesions and cell-extracellular matrix adhesions. The central role of anchoring junctions is played by
transmembrane adhesion proteins of which the major ones are cadherin and integrin. Which one of the following statements regarding cadherin and integrin is NOT correct?
(1) Generally, cadherin mediates attachment of cell to cell whereas integrin mediates attachment of cells to extracellular matrix
(2) Cadherin molecules of a specific subtype on one cell bind to cadherin molecules of the same or closely related subtype on adjacent cells
(3) Both cadherin and integrin are composed of two non-covalently attached glycoprotein subunits which span the cell membrane
(4) Integrin molecules generally act as extracellular matrix receptor
The statement that is NOT correct regarding cadherin and integrin is:
(3) Both cadherin and integrin are composed of two non-covalently attached glycoprotein subunits which span the cell membrane.
Explanation:
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(1) is correct: Generally, cadherin mediates cell-to-cell adhesion, while integrin mediates attachment of cells to the extracellular matrix (ECM).
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(2) is correct: Cadherins bind homophilically to cadherins of the same or closely related subtypes on adjacent cells, in a calcium-dependent manner.
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(3) is incorrect: Integrins are composed of two non-covalently associated subunits (alpha and beta) spanning the membrane, but cadherins are single-chain transmembrane proteins, not composed of two subunits.
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(4) is correct: Integrin molecules serve as principal receptors for ECM proteins, mediating cell-ECM adhesion and outside-in signaling.
Thus, the structural composition description in (3) does not apply to cadherins and is the incorrect statement.
Summary Table
| Statement | Correctness | Notes |
|---|---|---|
| Cadherins mediate cell-cell adhesion (1) | True | Calcium-dependent homophilic binding |
| Cadherins bind same subtype on adjacent cells (2) | True | Homophilic calcium-dependent adhesion |
| Both are two subunit glycoproteins (3) | False | Integrins are heterodimers; cadherins are single-chain proteins |
| Integrins act as ECM receptors (4) | True | Bind ECM proteins, mediate adhesion and signaling |
Conclusion
Statement (3) is incorrect because cadherins are not composed of two subunits like integrins. Understanding these molecular details helps clarify the distinct structural and functional roles of these key cell adhesion molecules.
1 Comment
Kajal
November 7, 2025Option 3