Outline the Roles of Plasma Membrane at the Surface of a Cell

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Outline the roles of membrane at the surface of the cell
The plasma membrane encloses the cell, defines it boundaries and maintains the essential differences between the cytosol and the extra-cellular environment. The separation of the internal and external environment maintains a constant internal environment which is essential for the cell to function efficiently. Membrane receptors can interact with specific molecules corresponding to stimuli such as hormones to generate a signal cascade which consequently stimulates or inhibits the internal activities of the cell. The process is referred to signal transduction. Another role would be the cell-cell recognition. Carbohydrates moieties of glycoproteins in cell membrane may act as recognition sites to help cells of the same type, identify and adhere to one another during tissue transformation as well as tissue interactions at a later stage of development. These recognition domains also provide the basis of rejection of foreign cells in the immune system. Cell recognition allows cells to exhibit contact inhibition as a growth control measure. The plasma membrane is also a site for formation of multi-enzyme complexes, they may anchor stake holding enzymes in a sequential manner to form a multi-enzyme complex for reactions of a common biochemical pathway to proceed more efficiently. The plasma membrane is selectively permeable and regulates the movement of substances across them which is important for a cell to function properly.

3. Describe and explain the fluid mosaic model of the cell surface membrane. In the fluid mosaic model, protein and lipid components move rapidly in the plane of the membrane. Membrane proteins are dispersed and individually inserted into the phospholipid bilayer, with only their hydrophilic regions protruding far enough from the bilayer to be exposed to water. This maximizes contact of hydrophilic regions of proteins and phospholipid with water while providing hydrophobic parts...
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