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Understanding Complex Lipids: Structures, Roles, and Types in Cellular Membranes

This guide explores the intricate world of complex lipids, fundamental components of cellular membranes. It covers the two main groups: phospholipids, which include glycerophospholipids and sphingolipids, and glycolipids that contain carbohydrates. Learn how these lipids form bilayers, provide fluidity and barriers, and transport substances in and out of cells. The fluid mosaic model illustrates their dynamic nature, while specific types like sphingomyelin and cerebrosides highlight their importance in nervous tissue. Discover their essential roles in maintaining cellular integrity and function.

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Understanding Complex Lipids: Structures, Roles, and Types in Cellular Membranes

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  1. Complex LipidsSections 13.4-13.8 By: Cassie Webb and Alyssa Keifer

  2. 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

  3. 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)

  4. 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

  5. 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

  6. 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.

  7. 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

  8. 13.6 What are Glycerophospholipids? • Structure similar to fats • Membrane components of cells throughout the body • Alcohol in it is glycerol

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

  10. 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

  11. 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

  12. 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.

  13. Properties • Alcohol sphingosine • A long-chain fatty acid connected to NH₂ • Ceramide • A combination of a fatty acid and a sphingosine • They may use different fatty acids

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

  15. 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

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