Serine glycerophospholipid structure

The simplest of the glycerophospholipids is phosphatidic acid, in which phosphate is linked to the third hydroxyl function, forming a phosphate ester. More complex glycerophospholipids are derivatives of phosphatidic acid in which one of several groups is attached commonly choline, ethanolamine, serine, or myo-inositol. Structures are collected in table 19.1. 

Cephalins are glycerophospholipids present in foods. They differ from lecithins by having ethanolamine or serine instead of choline in their structure. Could you differentiate between lecithins and cephalins on the basis of the three tests to be performed in this experiment ... 

In certain organisms, e.g. the non-photosynthetic diatom Nitzschia alba, lecithine was found to be replaced by its sulphonium analogue (a phos-phatidyl-S,S-dimethylmercaptoethanol) as cell membrane component (Anderson et al., 1976) it was concluded that S-containing amino acids (e.g. cysteine, methionine) rather than serine probably act as primary precursors of the glycerophospholipids and sphingolipids which are involved in the formation of hydrophobic layers in membrane structures. 

Similarly, you can write the structures of phosphatidylethanolamine PE and phosphatidyl-serine PS (Fig. 1.16). Now you know how to write the structure of the three main membrane glycerophospholipids. At pH 7, both PC and PE are zwitterions (i.e., bear a positive and a negative charge). In contrast, PS has one positive and two negative charges, so that this lipid is globally anionic. ... 

Lecithins and cephalins are two types of glycerophospholipids that are particularly abundant in brain and nerve tissues as well as in egg yolks, wheat germ, and yeast. Lecithins contain choline, and cephalins usually contain ethanolamine and sometimes serine. In the following structural formulas, the fatty acid that is used as an example is palmitic acid ... 

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