COMPLEX LIP

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STRUCTURES• Triglycerides are significant components of fat storage cells.• Complex lipids are important because they constitute the

main components of membranes.

CLASSIFIED IN 2 GROUPS• Phospholipids – contain an alcohol, 2 fatty acids, and a

phosphate group.• Two types• Glycerophospholipids- alcohol is a glycerol.• Sphengolipids – alcohol is sphingosine.

CONT’D • Glycolipids – complex lipids that contain carbohydrates.

ROLES• Complex lipids form the membranes around body cells and

around small structures inside the cells.• These are called Organelles.

• Unsaturated fatty acids are important components of these lipids.

• Most lipids contain at least one unsaturated fatty acids.

CELL MEMBRANES• Cell membranes separate cells from the environment and

provide transport for nutrients and waste products into and out of cells.• These membranes are called – Lipid Bilayers.

LIPID BILAYERS• The arrangement of lipid bilayers leaves the hydrophilic

heads projecting to the inner and outer surfaces of the membranes.

• The unsaturated fatty acids prevent the tight packing of the hydrophobic chains in the lipid bilayer, providing a liquid-like character to the membranes.

• Effect is similar to the one that causes unsaturated fatty acids to have lower melting points than saturated fatty acids.

LIPIDS CONT’D• The lipid part of the membrane serves as a barrier against

any movement of ions or polar compounds into and out of the cells.

MOSAIC MODEL• A mosaic model of membranes allows the passage of

nonpolar compounds by diffusion.

WHAT ARE GLYCEROPHOSPHOLIPIDS?• Very similar to fats • Membrane components of cells throughout the body• The alcohol is glycerol• If the alcohol is chlorine, a quaternary ammonium

compound, the glycerophospholipids are called phosphatidyl – cholines

• Common name is – Lecithin

LECITHIN• The typical lecithin molecule has stearic acid on one end

and linoleic acid in the middle. • Lecithin is a major component in egg yolk

• Includes both polar and nonpolar portions within one molecule.• Excellent emulsifier• Used in mayonnaise as well.

• Lecithin is a negatively charged phosphate group and a positively charged nitrogen from the choline.

• Lecithin is only one example of glycerophospholipids.

CEPHALINS• Similar to lecithins in every way except that, instead of

choline, they contain alcohols, such as ethanolamine, or serine.

PHOSPHATIDYLINOSITOLS (PI)• Another important group is phosphatidylinositols or (PI).

• Alcohol inositol is bonded to the rest of the molecule by a phosphate ester bond.

WHAT ARE SPHINGOLIPIDS?• Myelin → Coating of the nerve axons, contains a different

kinds of complex lipid.• Sphingolipids → alcohol portion is sphingosine.• Not randomly distributed in membranes.

CERAMIDE• The combination of a fatty acid and sphingosine is called the

ceramide portion of the molecule, because many of these compounds are also found in cerebrosides.

• The ceramide part of complex lipids may contain different fatty acids.

SPHINGOMYELIN• Sphingomyelin → most important lipids in the myelin

sheaths of nerve cells and are associated with diseases such as multiple sclerosis.

WHAT ARE GLYCOLIPIDS?• Complex lipids that contain carbohydrates and ceramides.

TYPES OF GLYCOLIPIDS• Cerebrosides – consists of ceramide, and mono or

oligosaccharides.• In cerebrosides the fatty acid of the ceramide part may contain either

18 carbon or 24 carbon chains.• Gangliosides – Contain a more complex carbohydrate

structure.

• The latter form is only found in these complex lipids*