They occur with lecithin, particularly rich in brain and nervous tissue.

Cephalins occur along with lecithin in all plant and animal cells. They are similar structure as that of lecithin but differ from lecithin in that the base attached to phosphoric acid is not choline. It may be one of the three bases, namely ethanolamine, serine, and inositol. Therefore, the three cephalins are known as follows:

Lecithin is readily hydrolysed by boiling with acid and alkalis. Lecithin is hydrolysed by enzymes called lecithinase. There are four different types of lecithinase occur in nature: lecithinase A, lecithinase B, lecithinase C, and lecithinase D. Lecithinase A is found in cobra venom. It is also present in spider venom and poisonous stings. Lecithinase A action…

They are white waxy substances, which become brownish when exposed to air and light, owing to autooxidation. This is due to the presence of unsaturated fatty acid in the molecule. They are soluble in alcohol and other fat solvents. They are hygroscopic and mix well with water to form cloudy, colloidal, and slimy solution. They…

Choline is present in egg yolk, liver, heart, kidney, and milk.

Choline is the tri ethyl hydroxylethyl ammonium hydroxide. Choline is the component of lecithin and sphingomyelin and hence an important constituent of phospholipid.   HO—H2C—H2C—N(CH3)3

Lecithin consists of one molecule of glycerol, esterified with two molecules of fatty acids; one of these fatty acid may be unsaturated and other saturated. It contains phosphoric acid and a nitrogenous base – choline. Two forms of lecithin, alpha lecithin, and beta lecithin are described. Alpha lecithin has the phosphoric acid and choline attached…

The important phospholipids are the following:

They are abundantly present in heart, brain, kidney, egg yolk, and soya bean.