Problem 21 - Objective Biology for NEET

Question

What is the function of tight junctio Open with (a) Protects from bacterial infection (b) Stop substance leaking across the tissue (c) Both (a) and (b) (d) Elasticity to the tissue

Step-by-Step Solution

Answer

The correct answer is (b). Tight junctions stop substances from leaking across the tissue.

Step 1: Understanding the Role of Tight Junctions

Tight junctions are part of the cell's adhesive system. They play a key role in maintaining the integrity and functioning of tissues by preventing substances from moving freely between cells. Thus, they help in creating a barrier within the tissue.

Step 2: Analyzing the Options

Option (a) suggests that tight junctions protect tissues from bacterial infections. While tight junctions do create a barrier, they are not primarily known for protection against bacteria. Option (b) states that tight junctions prevent substances from leaking across the tissue, which correctly describes their main role. Option (d) claiming that tight junctions provide elasticity to the tissue is incorrect as that is not their primary function.

Step 3: Choosing the Correct Answer

Based on the understanding and analysis, option (c) Both (a) and (b) seems to be incorrect as tight junctions are not primarily known to protect from bacteria. So, the correct answer should be option (b) which correctly states that tight junctions stop substances from leaking across the tissue.

Key Concepts

Cell Adhesive System

Tight junctions play a crucial role in the cell adhesive system. They are specialized structures that connect cells tightly together. Imagine brick walls; each brick needs mortar to stick together firmly. Similarly, cells need tight junctions to remain close and joined. This adhesive property forms a continuous lining that is essential for the seamless functioning of tissues.
Tight junctions are composed of specific proteins. These proteins create a seal between cells. This seal presses the cells close to each other and restricts any gaps.
Key proteins involved include claudins, occludins, and junctional adhesion molecules.

• Claudins: Major components of tight junctions that create selective permeability.
• Occludins: Regulate the diffusion of small molecules.
• Junctional Adhesion Molecules (JAMs): Contribute to junctional integrity and signal transductions.

These components together ensure that cells stick together, forming an impenetrable frontier around the tissue.

Tissue Integrity

Think of tissue integrity as the strength and unity within a fabric. Just like threads in a fabric are interwoven to ensure there are no holes, tight junctions interconnect cells tightly to maintain tissue integrity.
These junctions prevent cells from moving apart which ensures that tissues are stable and structured. This stability is particularly important in tissues that experience mechanical stress, like the digestive tract lining.
When tight junctions function properly, they help keep cells in defined shapes and locations, which supports the tissue as a whole.

• Prevents tissue disintegration.
• Maintains tissue shape.
• Supports cellular communication within tissues.

Together, these aspects allow tissues to perform their roles effectively without collapsing or tearing.

Substance Permeability

A critical function of tight junctions is controlling substance permeability. Imagine a selective barrier that allows only certain substances to pass, while blocking others. Tight junctions create such a barrier between cells.
This regulation ensures that nutrients don’t simply leak out of tissues, and harmful substances can’t seep in.
Additionally, they regulate the passage of ions, solutes, and other molecules in fluids across the cells. This precise control is vital for maintaining the internal environment of tissues.
Here are some factors tight junctions influence:

• Prevention of pathogen penetration.
• Regulation of ion flow and water balance.
• Selective transport of nutrients and waste.

By achieving this control, tight junctions play an essential role in normal bodily functions.

Barrier Function

The primary importance of tight junctions is their barrier function. Envision them as gates that control entry and exit around cells. This aspect of tight junctions fortifies a physical barrier and ensures that tissues are sealed tightly.
Without tight junctions, substances would move haphazardly, creating chaos within tissues, leading to possible complications and diseases.
They are vital in sensitive areas like the digestive system, where they prevent harmful substances from entering the bloodstream and ensure nutrients are properly absorbed.
Key benefits include:

• Protection against toxins and pathogens.
• Maintaining compartmentalization of different tissue layers.
• Supporting immune defense mechanisms.

Thanks to these functions, tight junctions support overall body homeostasis and health.