Difference Between Gap Junction and Tight Junction (with Comparison Chart)

The essential difference between the Gap junction and the Tight junction is that the first one is known to direct channel between cytoplasms of the adjacent cells, while the latter blocks the passage of solutes and water molecules between epithelial layers in vertebrates. Gap junctions are widely spread in the body of vertebrates, while tight junctions are only found in epithelial cells of the vertebrates.

The social interactions among the cells of the multicellular organism are the most fundamental that holds the cells together. Cells may adhere to one another through the cell-cell junction, or they may be surrounded by the extracellular materials secreted by them, so by one or the other means they cohere to form an organized multicellular structure.

The mechanism of attachment of cells and tissue and the way they work governs the architecture of the body, its strength, the arrangement and shape of different cells types. The channels between the cells form a pathway for communications that allow the cells to exchange the signals, coordinate in their behaviour and regulate the gene expressions.

The making and breaking of the cells to other cells and extracellular matrix defines the way cell work within the organism and guides the body to grow, develops and repairs by itself. Therefore, the machinery of cell adhesion, cell junctions, cell signaling, and extracellular matrix is essential for every aspect of the functions, development, and organization of a multicellular organism.

In regards with the cells, physical attachment is critical in both nonepithelial as well as in epithelial tissues, but junctions between cell-cell, or between cell-matrix vary in structure and functions a lot then just transmitting a signal. These four functions are – Anchoring junctions, Channel-forming junctions, Occluding junctions and signal-relaying junctions.

In this content, we will be studying the essential differences between one of the types of Occluding junction which is Tight junctions – that act as a barrier and lock the gaps between the cells in epithelia, and the Channel-forming junction which is Gap junction – that provides the channel between two linking cytoplasm of the adjacent cells.

Comparison Chart

Basis for Comparison	Gap Junction	Tight Junction
Meaning	Gap junction is known for providing cell-cell communication, which supports the cell signalling, electrical signalling and transfers of ions and other micromolecules.	The tight junction is known to seal the flow of fluids between adjacent cells, and it fills the cavities found between the cells, which are found in epithelial cells.
Also known as	Macula communicans and nexus.	Zonulae occludentes and occluding junctions.
Present in	All types of tissues, except in developed skeletal muscles.	It is present in vertebrates (nerve cells) of epithelia.
Protein name	Connexins.	Claudins and associated zonal proteins.
It consists of	The cytoplasmic channel which connects the cytoplasm of one cell to other and membrane proteins.	Plasma membranes, network of proteins (claudins) and other proteins which are compactly packed.
Role	1. Gap junctions are known for facilitating communications between cells, so we can say it mediates cell-cell communications between the cytoplasm of the two adjacent cells. 2. It provides the channel for the movements of amino acids, sugars, ions and other micromolecules as well as electrical signals.	1. Tight junctions have a mechanical role, where it prevents the passage for the transfer of solutes and water molecules between the epithelial layers. 2. It also checks the leakage of the extracellular fluid beyond the epithelial layer, as it forms a water-tight seal which prevents the material passing between cells.
Examples	Gap junctions support the movements in coordination with the muscles to support the childbirth.	The cells present in the intestine takes up the nutrients from the gut, the tight junction checks or blocks the unwanted materials entering the body through the epithelial cell membranes receptors, hence control the waste material to enter.

Definition of Gap Junction

Gap junction is known for bridging gaps between the adjacent cell and creates a direct path between the cytoplasm of the two cells. In plants, these linkages are known as plasmodesmata. However, the function is similar in both that provides connections between cells that allows the exchange of small molecules (about 1000 daltons) though not macromolecules.

A gap junction has four transmembrane proteins, out of them, six gets assembled to form – connexon or hemichannel. These connexons in the plasma membranes of two cells get aligned to create a channel between the interiors of two cells. Gap junctions consist of numerous connexon pairs in parallel, that a molecular sieve-like structure.

Different tissues have different features of gap junctions as they are formed from different combinations of connexins. Gap junctions are dynamic in structure, where new connexons are continually added to the periphery, and the old ones are removed from its center.

This junction plays an essential role in cells connections, as with this channel, the cytoplasm of the cells can share small molecules, and inorganic ions and hence electrically as well as chemically coupled. So, gap junctions are essential in coordinating the activities of active cells and in with other cells.

Definition of Tight Junction

In the body of the vertebrates, more than 60% of the cells types are epithelial. Likewise, the simple cell which encloses and partition the interior parts of its surfaces and cavities, so epithelial also encloses and partition the body of an animal, lining all cavities and surfaces and creating a special compartment for the various process to occur.

All kinds of epithelial cells, work as the semipermeable barriers which separate the fluids on the apical side and the basal side. This barrier forms the occluding junctions with the adjacent cells so that molecules are unable to move freely across the cell sheet. Such occluding junction found in vertebrates in the epithelia is known as tight junctions.

So, Occluding junctions – septate junctions in insects and molluscs and tight junctions in vertebrates – seal the intracellular space or gaps in epithelia and creates a barrier so that molecules are unable to diffuse through the cell sheet.

They also check the level of proteins in the apical and basolateral membrane domains of the epithelial cells. The major transmembrane proteins – claudins are known for occluding junctions, apart from there are many other members of the same family too, which forms the junction.

Key Differences Between Gap and Tight Junction

Following are the critical differences between Gap junction and Tight Junction:

Gap junction is known for providing cell-cell communication, which permits the cell signaling, electrical signaling, and diffusion of ions, water-soluble molecules and other micromolecules between the cytoplasm of adjacent cells. On the other hand, Tight junction performs the key task in holding the cells together into the epithelial tissues and blocks the unwanted materials entering the body through the epithelial cell membranes receptors, hence controls the waste material to enter.
Gap junction is also known as Macula communicans and nexus, and Tight junction is also known as Zonulae occludentes and occluding junctions.
Gap junction is found in all types of tissues (epithelial and non-epithelial tissues), except in developed skeletal muscles, whereas Tight junction is present in vertebrates (nerve cells) of epithelia (epithelial tissues).
The protein present in gap junction is Connexins, and in Tight junction, the proteins are Claudins and associated zonal proteins.
Gap junction has a cytoplasmic channel which connects the cytoplasm of one cell to other and membrane proteins, while in the tight junction has a network of proteins (claudins) and other proteins which are compactly packed.
Gap junctions are known for facilitating communications between cells, and hence known for mediating cell-cell communications between the cytoplasm of the two adjacent cells.
Gap junction also provides the channel for the movements of amino acids, sugars, ions, and other micromolecules as well as electrical signals.
Tight junctions have a mechanical role, where it prevents the passage for the transfer of solutes and water molecules between the epithelial layers. It also checks the leakage of the extracellular fluid beyond the epithelial layer and forms a water-tight seal which prevents the material passing between cells.

Similarities

Both gap junctions and tight junctions have a specialized channel known as connexons.
These are two types of cell junctions, found between two adjacent cells of vertebrates.
The functions of such junctions are mainly in cell-cell communications and hold the cells together to function properly. In both, the junctions, various proteins and plasma membranes of the cells play a significant role in creating a channel.

Conclusion

In this article we have studied about the gap junction and tight junction, in the Gap junction allows the rapid diffusion of micro-molecules and water-soluble molecules whereas tight junction seals the diffusion of proteins and lipids in the linings of the plasma membrane.