CELL MEMBRANE or Plasma Membrane Chaitali Barman Ray

CELL MEMBRANE. . (or Plasma Membrane) -Chaitali Barman Ray Asstt. Professor of Zoology v A thin(5 to 10 nm wide) or microscopic semi permeable limiting layer of cell protoplasm consisting of a fluid phospholipid bilayer with intercalated proteins serving as a boundary between the interior of a cell and its extracellular environment and regulates the passage of molecules in and out of the cytoplasm.

Chemical composition: Membranes from different sources vary in their composition…. v Membranes are lipid-protein assemblies in which the components are held together in a thin sheet by non covalent bonds. . components LIPIDS PROTEINS CARBOHYDRATES The plasma membrane of eukaryotic cells also contain carbohydrate. Depending on the species and cell type the carbohydrate content of plasma membrane ranges between 2 to 10 percent by weight.

FIGURE. . plasma memebrane

Membrane lipids. . Membranes contain a wide diversity of lipids all of which are amphipathic; that is they contain both hydrophilic and hydrophobic regions. Phosphoglycerides Sphingolipids Cholesterol

Integral protein (Transmembrane proteins) Peripheral proteins Lipid-anchored proteins (Located entirely outside (Located outside the lipid of the lipid bilayer) bilayer, on either the extracellular or cytoplasmic surface)

Membrane function: v Compartmentalization v Scaffold for biochemical activities v Providing a selectively permeable barrier v Trans porting solutes v Responding to external stimuli v Intercellular interaction v Energy transduction