The only phosphatidylserine conveys a net negative charge,

The table shows the different amounts of lipid type in several biological membranes. As seen in the table, the plasma membranes of bacteria, in this case E.coli, contain one main type of phospholipid and no cholesterol. Instead of fatty acids, lipids in archaea are usually composed of 20-25 carbon long prenyl chains; Prenyl and fatty acid chains are correspondingly hydrophobic and adaptable in thermophilic archaea, the longest lipid chains traverse the two leaflets, making the layer especially stable to high temperatures. Therefore, this shows that lipid bilayers can be made from molecules with same characteristics but with varied molecular designs.  The plasma membrane of liver cell, mitochondria and red blood cells of eukaryotic cells are different that those of prokaryotes, not only in having a blend of various phospholipids but also in containing huge amounts of cholesterol. Phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and sphingomyelin are the four major phospholipids that predominates in the numerous mammalian cells’ plasma membrane. It is important to note that only phosphatidylserine conveys a net negative charge, the remaining three major phospholipids carries one positive and one negative charge which are electrically neutral at physiological pH. Altogether, these four phospholipids contributes to more than half the mass of lipid in most membranes. In addition, other phospholipids such as the inositol phospholipids are available in minute amounts but are practically vital. The inositol phospholipids, for instance, have an essential role in cell signalling.  Examination of membrane lipids by mass spectrometry has uncovered that a typical eukaryotic cell membrane’s lipid composition is significantly more complex than initially thought. These membranes are composed of a variety of about 500-2000 various lipid species with even the red blood cell’s simple plasma membrane having more than 150. While some of this complexity mirrors the combinatorial variation in head groups, hydrocarbon chain lengths, and desaturation of the major phospholipid classes, few membranes likewise contain numerous structurally distinct minor lipids, in any event some of which have imperative functions. The inositol phospholipids, for instance, are available in minute amounts in animal cell membranes and have significant role in assisting membrane traffic and in cell signaling


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