Simple lipids types

Lipids include many types of compounds containing a wide variety of functional groups. You could easily prepare a solution of lipids by grinding a T-bone steak in a blender and then extracting the puree with chloroform or diethyl ether. The resulting solution of lipids would contain a multitude of compounds, many with complex structures. To facilitate the study of lipids, chemists have divided this large family into two major classes complex lipids and simple lipids. 

Nonetheless, the most fascinating and complex lipid type is sterols. They have a rigid steroid ring stmcture, which is a simple hydroxyl group as their polar head and a short flexible tail at the other end of the molecule. Of the many sterols found, two sterols exist whose significance in cells is above the others. Cholesterol is abundant in eukaryotic cells, and ergosterol is abundant in fungi. The reasons why nature has chosen these two specific sterols are not well understood. One is tempted to think that the properties of all sterols should be similar,... 

Simple (or neutral) lipids release two types of products, e.g., fatty acids and glycerol. The most abundant simple lipids are the triacylglycerols. 

Based on the features of chromatographic separation, lipids are classified into simple and complex molecules [2]. Simple lipids are those that yield mostly two types of primary products per molecule upon hydrolysis (e.g., fatty acids and their derivatives, MAG) complex lipids yield three or more primary hydrolysis products per molecule (e.g., PC, TAG, DAG). These hydrolysis products include fatty acids, phosphoric acid, organic bases, carbohydrates, glycerol, and many more components. 

Simple lipids - those which on saponification yield at most two types of primary hydrolysis product (fatty acids, glycerol, etc.) per mole, e.g. triacylglycerols and cholesterol esters. 

CLASSIFICATION. Lipids are often classified into three major groups (1) simple lipids (2) compound lipids and (3) derived lipids. When fatty acids are esterified with alcohols, simple lipids result. If compounds such as choline or serine are esterified to alcohols in addition to fatty acids, compound lipids result. The third type of lipid, derived lipids, results from the hydrolysis or enzymatic breakdown of simple and compound lipids. 

Szostak et al. worked on the basis of a simple cellular system which can replicate itself autonomously and which is subject to Darwinian evolution. This simple protocell consists of an RNA replicase, which replicates in a self-replicating vesicle. If this system can take up small molecules from its environment (a type of feeding ), i.e., precursors which are required for membrane construction and RNA synthesis, the protocells will grow and divide. The result should be the formation of improved replicases. Improved chances of survival are only likely if a sequence, coded by RNA, leads to better growth or replication of membrane components, e.g., by means of a ribozyme which catalyses the synthesis of amphiphilic lipids (Figs. 10.8 and 10.9). We can expect further important advances in the near future from this combination ( RNA + lipid world ). 

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