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The cell membrane is the outer most layer of the cell that separates cytoplasm from the external environment.this is also known as plasma membrane.the cell membrane defines the shape nd size of the cell,encloses the cytoplasm from and protect it from external environment.the internal environment of cell is differ frrom outside.Inside a cell,one finds a very specific composition of various substances which maintain a balance.The cell membrane plays a crucial role in maintaining this balance.

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Like all other cellular membranes, the plasma membrane consists of both lipids and proteins. The fundamental structure of the membrane is the phospholipid bilayer, which forms a stable barrier between two aqueous compartments. In the case of the plasma membrane, these compartments are the inside and the outside of the cell. Proteins embedded within the phospholipid bilayer carry out the specific functions of the plasma membrane, including selective transport of molecules and cell-cell recognition.
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