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Lipids

Lipids. Migrate over-water 2,400 miles. Water insoluble (hydrophobic) Non-polymeric structure Energy storage, membrane constituent, hormone signaling. I. Fatty Acids: Fuel & Membrane Building Blocks. Hydrocarbon with carboxylic acid head group Highly reduced carbon source

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Lipids

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  1. Lipids Migrate over-water 2,400 miles Water insoluble (hydrophobic) Non-polymeric structure Energy storage, membrane constituent, hormone signaling

  2. I. Fatty Acids: Fuel & Membrane Building Blocks Hydrocarbon with carboxylic acid head group Highly reduced carbon source Ionized at neutral pH (-ate not -ic acid form) Soap: fatty acid salt Which fatty acid is more reduced? What makes soap a good cleaner?

  3. Naturally Occurring Animal Fatty Acids: Common and Systemic Names

  4. Melting Point and Membrane Fluidity Shorter chain length lowers melting point cis Double bond lowers melting point Unsaturated fatty acids (oils) lower melting point versus saturated fatty acids (solid) Predict the oil composition from palm versus canola plants.

  5. Health Versus Fat Quantity and Quality Trans fats correlated with high blood cholesterol/cardiovascular disease (inflammation?) Cis polyunsaturated fatty acids essential for the diet (inhibit blood clotting, reduce heart attack risk) Vegetable oil (linolenate) Shell fish/cold water fish (EPA/DHA)

  6. II. Triacylglycerol in Energy Storage Anhydrous fat /gram stores 6x energy of hydrated glycogen Triacylglycerol storage site – adipose tissue Sugar storage 18 hrs; triacylglycerol storage several weeks

  7. III. Phospholipids: Major Class of Membrane Lipids Phosphatidate: key intermediate in phosphoglyceride biosynthesis and membranes Lipid bilayer

  8. Common Membrane Phosphoglycerides What does the color coding for green, blue and pink represent?

  9. Membrane Sphingolipids Amino alcohol backbone – sphingosine Sphingomyelin – sphingosine with a fatty acid amide linkage and choline; abundant in nerve cell membranes Cerebroside – sphingosine with a sugar residue (aka glycolipid)

  10. IV. Glycolipids Gangliosides – sphingosine with multiple sugar residues Sugars are extracellular A, B and O blood typing Multiple sugar units

  11. V. Steroids Tetracyclic ring structure (3 cyclohexane fused with cyclopentane) Facilitate lipid digestion Membrane fluidity buffer How does cholesterol orientate in the membrane?

  12. Lipoproteins Protein attachment to the surface of a membrane N-Myristoylglycine

  13. Membrane Component from a High-Temperature Organism What are the chemical differences in this lipid from standard membrane lipids? What impact do these alterations have on lipid behavior?

  14. Phospholipids and Glycolipids Self-Assemble to Form a Lipid Bilayer • Driving Forces: • H-bonding • Hydrophobic effect • Electrostatic interactions • Van der Waal’s attractions (close packing)

  15. Membrane Fluidity: Temperature, Cholesterol and Fatty-Acid-Composition Regulated How does membrane composition alter with elevated temperature?

  16. Significant Lateral Albeit Minimal Transverse Lipid Movement

  17. Liposome for Potential Drug Delivery

  18. Lipid Bilayer Small-Molecule Permeability Unassisted membrane crossing linked with H2O and non-polar solvent solubility * Protein assisted transport * * * * *

  19. Peripheral and Integral Membrane Proteins Different membrane orientation (a and e), surface position (f and e) and membrane componentassociation (d, and g) What tethers peripheral proteins to the membrane? What secondary structure is common in membrane hydrophobic regions?

  20. Alpha Helices in the Integral Protein Bacteriorhodopsin Bacteria light-harvesting protein that generates proton gradient α-Helix most common 2° membrane structure Helical (yellow) and charged (red) residues

  21. Chapter 8 Problems: 1, 3, 5, 7, 9, 19, 21, 23 and 25

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