NEET BIOLOGY

Detailed explanation-1: -Tight junctions are virtually (but also partly selectively) impermeable seals that encircle cells and bind them together into leakproof sheets. In other words, the plasma membranes of adjacent cells essentially fuse together tightly in order to limit the leakage of various substances between the two cells.

Detailed explanation-2: -The purpose of tight junctions is to keep liquid from escaping between cells, allowing a layer of cells (for instance, those lining an organ) to act as an impermeable barrier. For example, the tight junctions between the epithelial cells lining your bladder prevent urine from leaking out into the extracellular space.

Detailed explanation-3: -Occluding junctions Proteins in the membrane of adjacent cells called occludin interact with each other to produce this tight seal. In the cytoplasm of the cell, occludin interacts with the actin cytoskeleton via another proteins called ZO-1.

Detailed explanation-4: -Tight junctions prevent the passage of molecules and ions through the space between plasma membranes of adjacent cells, so materials must actually enter the cells (by diffusion or active transport) in order to pass through the tissue.

Detailed explanation-5: -Forming continuous seals around the cells, tight junctions prevent leakage of extracellular fluid across a layer of epithelial cells.