Download Complex Lipids

STRUCTURES
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Triglycerides are significant components of fat storage cells.
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Complex lipids are important because they constitute the main components of
membranes.
CLASSIFIED IN 2 GROUPS
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Phospholipids – contain an alcohol, 2 fatty acids, and a phosphate group.
• Two types
• Glycerophospholipids- alcohol is a glycerol.
• Sphengolipids – alcohol is sphingosine.
CONT’D
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Glycolipids – complex lipids that contain carbohydrates.
ROLES
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Complex lipids form the membranes around body cells and around small
structures inside the cells.
• These are called Organelles.
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Unsaturated fatty acids are important components of these lipids.
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Most lipids contain at least one unsaturated fatty acids.
CELL MEMBRANES
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Cell membranes separate cells from the environment and provide transport for
nutrients and waste products into and out of cells.
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These membranes are called – Lipid Bilayers.
LIPID BILAYERS
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The arrangement of lipid bilayers leaves the hydrophilic heads projecting to the
inner and outer surfaces of the membranes.
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The unsaturated fatty acids prevent the tight packing of the hydrophobic chains in
the lipid bilayer, providing a liquid-like character to the membranes.
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Effect is similar to the one that causes unsaturated fatty acids to have lower
melting points than saturated fatty acids.
LIPIDS CONT’D
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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
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A mosaic model of membranes allows the passage of nonpolar compounds by
diffusion.
WHAT ARE GLYCEROPHOSPHOLIPIDS?
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Very similar to fats
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Membrane components of cells throughout the body
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The alcohol is glycerol
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If the alcohol is chlorine, a quaternary ammonium compound, the
glycerophospholipids are called phosphatidyl – cholines
• Common name is – Lecithin
LECITHIN
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The typical lecithin molecule has stearic acid on one end and linoleic acid in the
middle.
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Lecithin is a major component in egg yolk
• Includes both polar and nonpolar portions within one molecule.
• Excellent emulsifier
• Used in mayonnaise as well.
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Lecithin is a negatively charged phosphate group and a positively charged
nitrogen from the choline.
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Lecithin is only one example of glycerophospholipids.
CEPHALINS
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Similar to lecithins in every way except that, instead of choline, they contain
alcohols, such as ethanolamine, or serine.
PHOSPHATIDYLINOSITOLS (PI)
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Another important group is phosphatidylinositols or (PI).
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Alcohol inositol is bonded to the rest of the molecule by a phosphate ester bond.
WHAT ARE SPHINGOLIPIDS?
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Myelin → Coating of the nerve axons, contains a different kinds of complex lipid.
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Sphingolipids → alcohol portion is sphingosine.
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Not randomly distributed in membranes.
CERAMIDE
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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.
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The ceramide part of complex lipids may contain different fatty acids.
SPHINGOMYELIN
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Sphingomyelin → most important lipids in the myelin sheaths of nerve cells and
are associated with diseases such as multiple sclerosis.
WHAT ARE GLYCOLIPIDS?
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Complex lipids that contain carbohydrates and ceramides.
TYPES OF GLYCOLIPIDS
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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.
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Gangliosides – Contain a more complex carbohydrate structure.
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The latter form is only found in these complex lipids*