1. Lipids (fats) Ooh, totally aliphatic!

2. Lipids characteristics Efficient storage of energy !!! Nonpolar or low polarity –Many have a polar end (hydrophilic) and a nonpolar end (hydrophobic) = amphipathic molecules Insoluble in water Two major groupings: –Hydrolyzable –Nonhydrolyzable

4. Fatty acids in nature: Saturation: –Saturated –Unsaturated Monounsaturated Polyunsaturated Usually cis Number of carbons are even Linear molecules: not branched

6. Omega number (ω) This indicates how many carbons from the far end of the fatty acid to the first double bond ω-1 is the methyl group at the end farthest from the COOH group The omega number of linoleic acid would be ____

7. Effect of saturation on melting points Examine the chemical structures on the next slide. How well would a saturated chain pack into a solid compared to an unsaturated chain? Influence on melting point:

9. Melting points of fatty acids Animal fats are generally ________ at room temperature Vegetable fats are generally ________ at room temperature Which do you expect have more double bonds?

11. Most of our animal fat and plant oil intake is triacylglycerols; get hydrolyzed and absorbed in gut, then reassembled: energy storage A major membrane lipid component: note hydrophilic end of molecule Another major membrane lipid: note hydrophilic end of molecule again! Another membrane lipid, but note saccharide attachment: think cell- recognition ie blood groups?

12. Triacylglycerols One glycerol + three fatty acids = one triacylglycerol –Triple esterification –Reverse is hydrolysis (3x over) –Base hydrolysis of triacylglycerol → soap (saponification) Catalytic hydrogenation of unsaturated fats –Unsaturated triacylglycerol → saturated triacylglycerol –Alkene → alkane Triacylglycerol = triglyceride Energy source; energy reserves for the future

14. Steroids : note the core ring structure of these molecules All steroids have this basic unit, although sometimes it is a little disguised

15. Steroids Cholesterol –Incorporated in cell membranes –Precursor to other animal steroids –Body can synthesize all it needs even if cholesterol is completely removed from the diet. It’s that important.

16. Steroid hormones Need only very low concentrations Adrenals: –Cortisol (fight or flight) –Aldosterone (regulate electrolytes in blood) Sex hormones Chemical messengers and regulation of cell functions

17. Vit D can be named as a cholesterol derivative – do you see the relationship?

18. Vitamin D biosynthesis – notice compartmentation (location) of different steps

19. Just to see these two drawn out to full chain length:

20. Eicosanoids: Eicosane = ________ Eicosanoids are involved in:

21. Membranes: Optimal proportions of Lipids Proteins Cholesterol for strength and function of that type of cell