The fundamental function of the plasma membrane is that of protection. Thus the cell can maintain a constant internal environment, irrespective of changes that may occur outside. However, the cell membrane, while protecting the cell from a variable external environment, must allow selective communication with the exterior. Arrangements must be made for the controlled passage of nutrients into the cell, and the removal of waste products from it. Plasma membranes, therefore, have associated with them a range of transfer systems which enable molecules to pass through the membrane in a specific manner. In most prokaryotic cells, no intracellular membranes are present, and the cell interior is a single compartment bounded only by the plasma membrane. Eukaryotic cells, however, have numerous intracellular membrane systems which form a series of intracellular compartments, within which many of the processes of metabolism occur.
KeywordsCell Interior Soluble Enzyme Electrochemical Gradient Membrane Function Intracellular Membrane
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