subject: Function Of Plasma Membrane [print this page] Introduction to function of plasma membrane:
Plasma membrane is the protective membrane present surrounding all living cells. The main function of cell membrane is to separate interior of a cell from external environment. It is semi permeable membrane made up of lipoprotein bilayer. It consists of various biomolecules mainly including protein and lipid.
It is selectively permeable and amphipathic in nature. Lipid layer mainly consists of phospholipids which are amphipathic in nature i e contains both hydrophilic and hydrophobic region. Mainly two types of protein are present in plasma membrane: Transmembrane protein or integral protein and Peripheral protein. These lipid part and 2 types of protein plays important role in function of plasma membrane.
Plasma Membrane Function
Function of plasma membrane is important in survival of all living cells. It not only protects the interior part of cell also helps the cells to maintain its shape. Main function of plasma membrane is as follows:
Protect and separate the interior part of cell (protoplasm) from external environment.
Maintain specific shape of the cell.
Act as semipermeable or selective barrier as it does not allow entry of all molecules inside the cell.
Help to adhere with adjacent cells to form tissue.
Maintains connection with adjacent cells via pores on membrane known as plasmodesmata(in plants)and desmosome(in animals)
Receptor proteins present on cell surface(in plasma membrane) plays important role in cell signalling.
Helps in transport across the membrane via osmosis and diffusion. Allow some other processes of transport also.
Allow transport of molecules(mainly protein) against concentration gradient via active transport.
Contains ion channels which help in active transport.
Function of plasma membrane also include exocytosis (excretion of waste outside the cell) and endocytosis (intake of large particles inside the cell).
Function of plasma membrane of some cells (phagocytes) include important role in immunity
Function of Different Parts of Plasma Membrane
Phospholipid layer act as barrier between two compartment of cell.
Long hydrocarbon chain of fatty acids present in lipid layer maintains softness and flexibility of plasma membrane.
Function of cholesterol present in animal plasma membrane is adjust fluidity of the membrane. At high temperature, cholesterol decrease fluidity of the plasma membrane and at high temperature it shows opposite effect on membrane.
Function of membrane protein of RBC- a) A pheripheral protein, spectrin helps to maintain cytoskeleton of erythrocyte. b) Ankyrin maintains the connection between cytoskeleton and integral protein.
Porins and aquaporins- Porins are only present in bacterial plasma membrane like E.coli and act as hole through which passive diffusion can take place. Porins allow transport of small molecules like sugar, amino acids and ions.
Aquaporins are water channels present in both bacterial and eukaryotes like plant and human plasma membrane.
Result of disruption of plasma membrane
Plasma membrane can be disrupted by detergents or surfectants like Sodium dodecyl sulphate (SDS), Sodium lauryl sulphate (SLS) etc. Disruption of cell membrane release and expose cellular organelles inside the cell. This leads to death of the cell. These agents are used to reduce number of bacteria on a surface. This proves presence of plasma membrane is essential for survival of all living cells.
