Complex Lipids Sections By: Cassie Webb and Alyssa Keifer

13.4 What are the Structures of Complex Lipids?  Main components of membranes  Classified into two groups  Phospholipids  Contain an alcohol, 2 fatty acids, and a phosphate group  Two types  Glycerophospholipids and sphingolipids  Glycolipids  Complex lipids contain carbohydrates

13.5 What Role Do Lipids Play in the Structure of Membranes?  Complex lipids form membranes around body cells and small structures inside the cells (organelles)

Unsaturated Fatty Acids  Lipid molecules in bilayer contain at least one  Prevent tight packing of hydrophobic chains  Provides a liquid-like character to membranes  Similar effect causes lower melting points than saturated

Membranes  Separate cells from external environment and provide the transportation for nutrients and waste products into and out of the cells  Made of lipid bilayers  Two layers of complex lipid molecules arranged tail to tail  Hydrophobic  Get as far from water as possible  Hydrophilic  On the surface

Membranes cont.  Lipid part acts as barrier against movement of ions or polar compounds in or out.  Protein molecules located on the surface, partly, or fully in the bilayer  Polar compounds transported through protein channels or active transport.

Fluid Mosaic Model  Allows the passage of nonpolar compounds by diffusion  Mosaic: meaning topography of bilayers  Fluid: meaning free lateral motion in bilayers making it liquid-like

13.6 What are Glycerophospholipids?  Structure similar to fats  Membrane components of cells throughout the body  Alcohol in it is glycerol

Glycerophospholipids Composed of  2 of 3 groups are esterified fatty acids  May be any long-chain carboxylic acids with or without double bonds  3 rd group is esterified by a phosphate group  Esterified to another alcohol

Letchin  Another name  A major component of egg yolk  Both polar and nonpolar portions in one molecule  good emulsifier  Example: mayonnaise  Cephalins  Similar to letchins  Contain different alcohols

PI (phosphatidylinositol)  The alcohol inositol is bonded to rest of the molecule by phosphate ester bond  Fundamental structural parts of membrane  In the form of PIP2 serves as a signaling molecule in chemical communication

13.7 What are Sphingolipids?  They were discovered in 1874 by Johann Thudichum  Named after a monster from Greek mythology the sphinx  A creature who devoured all who could not provide the correct answers to the riddles.

Properties  Alcohol sphingosine  A long-chain fatty acid connected to NH ₂  Ceramide  A combination of a fatty acid and a sphingosine  They may use different fatty acids

Sphingomyelins  They are the most important lipids in the myelin sheaths of the nerve cells.  Associated with diseases  Example: multiple sclerosis

13.8 What are Glycolipids?  Complex lipids that contain carbohydrates and ceramides  Cerebrosides are one group  They contain a ceramide mono- or oligosaccharide  Occur primarily in the brain and nerve synapses  Gangliosides are another group  Have a more complex carbohydrate structure