Column X represents the type of junctions and column Y represents the proteins associated with the junctions. Column X Column Y A. Anchoring junction i. Claudins B. Occluding junction ii. Delta-Notch C. Channel-forming junction iii. Desmoglein D. Signal-relaying junction iv. Connexin Which one of the following options is a correct match between terms of Columns X and Y?
A - iii, B - i, C - iv, D - ii
Cell junctions are vital structures in tissues that hold cells together and facilitate communication between them or between cells and the extracellular matrix. Different types of junctions serve specific functions and are characterized by distinct protein components.
Junction Types and Functions
Here is a brief overview of the junction types listed in Column X:
- Anchoring junctions: These junctions provide mechanical strength to tissues by linking the cytoskeleton of adjacent cells or linking cells to the extracellular matrix. They include adherens junctions and desmosomes.
- Occluding junctions: Also known as tight junctions, these seal the gaps between cells, preventing the passage of molecules and ions through the intercellular space (paracellular pathway).
- Channel-forming junctions: These junctions create direct channels between the cytoplasm of adjacent cells, allowing small molecules and ions to pass through. Gap junctions are the primary example.
- Signal-relaying junctions: These junctions allow signals to be transmitted directly from one cell to another, often involving cell-surface proteins that interact.
Protein Associations
Column Y lists specific proteins or molecules associated with these junction types:
- Claudins: These are key transmembrane proteins found in tight junctions (occluding junctions).
- Delta-Notch: This represents a classic signaling pathway involving direct cell-to-cell interaction where Delta protein on one cell binds to Notch receptor on an adjacent cell, initiating signal transmission. This is an example of signal relaying through cell-cell contact.
- Desmoglein: This is a type of cadherin protein found in desmosomes, which are a type of anchoring junction.
- Connexin: These proteins assemble to form connexons, which are the channels that make up gap junctions (channel-forming junctions).
Based on these associations, we can match the junction types from Column X with the proteins/molecules from Column Y.
Matching Columns X and Y
Let's match each junction type with its corresponding protein/molecule:
| Column X (Junction Type) | Correct Match (Column Y) | Explanation |
|---|---|---|
| A. Anchoring junction | iii. Desmoglein | Desmogleins are component proteins of desmosomes, a type of anchoring junction. |
| B. Occluding junction | i. Claudins | Claudins are essential proteins that form the seals in tight junctions (occluding junctions). |
| C. Channel-forming junction | iv. Connexin | Connexins form the channels in gap junctions, which are channel-forming junctions. |
| D. Signal-relaying junction | ii. Delta-Notch | The Delta-Notch pathway is an example of direct cell-to-cell signaling facilitated by interacting proteins at the cell surface, acting as a signal-relaying junction. |
The correct matching is therefore: A - iii, B - i, C - iv, D - ii.
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