Membranes

Membranes form boundaries both around the cell (the plasma membrane) and around distinct subcellular compartments example for Nucleus, mitochondria, lysosomes, etc. They act as selectively  permeable  barriers allowing  the  inside  environment  of  the  cell  or  organelle  to  differ  from  the outside.  Membranes are included in signaling procedures; they hold specific receptors for external stimuli and are involved in both chemical and electrical signal generation. All membranes contain two basic parts like: proteins and lipids. Some membranes also hold carbohydrate.  The work of lipid protein and carbohydrate varies from one membrane to another. For instance, the inner mitochondrial  membrane  has a huge amount  of protein than lipid due to the presence  of numerous  protein complexes  included  in oxidative  phosphorylation  and electron  transfer, although the myelin sheath membrane  of nerve cells, that serves to insulate the cell electrically has a larger proportion of lipid.