Extracellular Matrix or Cell Coat

 Extracellular Matrix or Cell Coat

Cell coat is a distinct  layer of glycocalyx observed  in the outer surface of cells in many animals  and protistans. It is made of Oligosaccharides. Cell coat is thickened  and strengthened  by the  deposition silicon, calcium  and other salts.


Animal cells have an elaborate extracellular matrix ( ECM) instead of cell wall.The ECM consists mainly of glycoproteins ( oligosaccharides covalently bonded to protrins). There are often 3 types of glycoproteins.  The most abundant glycoprotein is collagen that forms strong fibres. The collagen fibres are embedded in a network of the other glycoproteins named proteoglycans.The latter are specially rich in carbohydrates ( up to 95% ). The third type of glycoproteins in ECM are fibronectins. The glycoproteins bind to the receptor proteins called integrins that are a part of plasma membrane.  The integrins span the cell membrane and are connected to the microfilaments of the cytoskeleton on the inner side. This linkage can transmit changes in the cell's external environment to its interior and vice versa.


(i) The ECM protects the cell.

(ii) It supports and maintains the form of the cell.

(iii) It helps in recognising  similar cells during tissue formation. 

(iv) It keeps the cells adhered to each other and coordinates activities of all the cells in a tissue.

(v) It also aids the white blood corpuscles in identifying microbes for defence. 

(vi) It transmits changes between external environment and cell's interior. 

(vii) ECM of erythrocytes contains antigens which form the basis of blood groups.

(viii) Cell coat is protective in nature.

(ix) It provides shaped to the cells.

(x) Cell coat is involved  in histocompatibility. 


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