Phospholipids

Phospholipids, or glycerol phospholipids, are derivatives of phosphatidic acid (glycerol-3-phosphoric acid). According to the type of substituent attached to phosphatidic acid, phospholipids are further divided into:


 * 1)  Phosphatidylcholines (lecithins)
 * 2)  Phosphatidylethanolamines (kephalins)
 * 3) Phosphatidylserines
 * 4)  Plazmalogens
 * 5)  Phosphatidylinositols

Phosphatidylcholines (lecithins)



 * They contain choline, a quaternary nitrogen base
 * They are a part of the cell membrane
 * A large part of the body's supply of choline (important for the transmission of nerve impulses)
 * Waxy, colorless compounds with hydrophilic and hygroscopic features
 * They form colloid solutions in the water, create internal salts, reduce surface tension, good emulsifying agents
 * Easily hydrolyzed in the body due to the action of phospholipases
 * Dipalmitoyllecithin – surfactant

Phosphatidylethanolamines (kephalins)

 * They contain ethanolamine bound by an ester bond to the second acid group of phosphoric acid
 * Similar character as phosphatidylcholines

Phosphatidylserine



 * It contains serine amino acid
 * It is found in most tissues

Plazmalogens

 * The fatty acid is replaced at position 1 by an ether-linked higher unsaturated alcohol
 * Similar to lecithins and kephalins
 * Synthesized on peroxisomes by desaturation of 3-phosphoethanolamine derivatives (requires molecular oxygen, cytochrome b5, NADPH+ + H+ for the synthesis)
 * There are 3 types of plasmalogens: choline, ethanolamine, serine
 * Most of the phospholipids in mitochondria are plasmalogens
 * Choline plasmalogen, the so-called platelet-activating factor (PAF), is a mediator of hypersensitivity, acute inflammatory reaction and anaphylactic shock. The IgE antigen stimulates its production. When PAF is released, platelet aggregation and serotonin secretion occur

Phosphatidylinositol



 * They contain inositol, a sugar alcohol
 * Part of cell membranes, where they significantly influence its permeability
 * A source of arachidonic acid, which is the starting material for the formation of eicosanoids
 * Important for the transport of fats by blood and lymph
 * After stimulation by a certain hormone, phosphatidylinositol-4,5-bisphosphate is split into diacylglycerol and inositol triphosphate - these substances act as an internal signal or second messenger

Related articles

 * Phosphatidylcholine
 * Sphingolipids
 * Lipids
 * Mastné kyseliny (czech wikiskripta)

Used literature