The picture shows an EM of a desmosome formed between two cells. Notice the phase dense material between the two cell membranes, which is mad up of transmembrane linker glycoproteins e.
Also notice the intermediate filaments running from the desmosome into the cytoplasm. Other proteins run across the membrane into the intracellular space, to connect the two cells together. These 'transmembrane linker' proteins are called desmoglein and desmocollin, which are types of cadherin. These look similar to desmosomes, but are different functionally, and in their content.
The connect the basal surface of epithelial cells via intermediate filaments to the underlying basal lamina. The transmembrane proteins of hemidesmosomes are not cadherins, but another type of protein called integrin. This electron micrograph shows a Hemidesmosome H , and two of the three layers of the underlying basal lamina. LL - lamina densa, LD - lamina lucida. Integrins in the plasma membrane link the cell to the extra-cellular matrix. Gap junctions are the most widespread of all cell junctions in animal tissues.
Gap junctions thus couple cells electrically and metabolocially, enabling cells to communicate with each other directly. Keywords Keywords for this Article. Save Cancel. Share Cancel. Revoke Cancel. Flag Inappropriate The Content is.
Flag Content Cancel. Delete Content. Delete Cancel. Tight junctions blue dots between cells are connected areas of the plasma membrane that stitch cells together. Adherens junctions red dots join the actin filaments of neighboring cells together. Desmosomes are even stronger connections that join the intermediate filaments of neighboring cells. There are some differences in the ways that plant and animal cells do this. Plasmodesmata are junctions between plant cells, whereas animal cell contacts include tight junctions, gap junctions, and desmosomes.
In general, long stretches of the plasma membranes of neighboring plant cells cannot touch one another because they are separated by the cell wall that surrounds each cell. How then, can a plant transfer water and other soil nutrients from its roots, through its stems, and to its leaves?
Such transport uses the vascular tissues xylem and phloem primarily. Figure 2. A plasmodesma is a channel between the cell walls of two adjacent plant cells.
Plasmodesmata allow materials to pass from the cytoplasm of one plant cell to the cytoplasm of an adjacent cell. A tight junction is a watertight seal between two adjacent animal cells Figure 3. The cells are held tightly against each other by proteins predominantly two proteins called claudins and occludins. Figure 3. Tight junctions form watertight connections between adjacent animal cells. Proteins create tight junction adherence. This tight adherence prevents materials from leaking between the cells; tight junctions are typically found in epithelial tissues that line internal organs and cavities, and comprise most of the skin.
For example, the tight junctions of the epithelial cells lining your urinary bladder prevent urine from leaking out into the extracellular space.
Also found only in animal cells are desmosomes , which act like spot welds between adjacent epithelial cells Figure 4. Short proteins called cadherins in the plasma membrane connect to intermediate filaments to create desmosomes. The cadherins join two adjacent cells together and maintain the cells in a sheet-like formation in organs and tissues that stretch, like the skin, heart, and muscles. Figure 4.
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