Final answer:
Adherens junctions rely on cadherin proteins to bind cells together, which connect to plaque proteins and intermediate filaments, adding strength to tissue cohesion. They come in different forms, such as belt desmosomes and spot desmosomes, and are distinct from other junctions like tight junctions and gap junctions in function and structure.
Step-by-step explanation:
Adherens Junctions in Cell Cohesion
Cells within tissues are held together by structures known as adherens junctions, which are crucial for maintaining the structural integrity of tissues. The cadherins are a type of protein that play a pivotal role in this process. These transmembrane proteins extend out of the cell membrane and interact with cadherins on neighboring cells, effectively acting as a 'glue'. The intracellular portion of cadherins connects to plaque proteins, which in turn are bound to intermediate filaments such as keratin, providing additional strength and stability to the cellular adhesion.
There are different types of adherens junctions, including the belt desmosomes (zonula adherens), which encircle the cell, and spot desmosomes (macula adherens), which are localized to points of cell-cell contact. These junctions ensure that mechanical stress is evenly distributed among cells, contributing to the resilience of tissues against physical forces.
Besides adherens junctions, other types of cell-cell junctions include tight junctions, which prevent the leakage of extracellular fluid across the cellular layer and gap junctions, which facilitate communication between cells by allowing the passage of ions and small molecules. Unlike adherens junctions, gap junctions do not contribute to mechanical stability but to the tissue's functional coordination.