1. 18.4 Chemical properties of fats and oils
1. Hydrolysis
Reverse of esterification
Forms carboxylic acids (FAs) and alcohol (glycerol)
Catalyst = acid or enzyme (lipase)

2. Chemical reactions of TAGs
2. Saponification (hydrolysis in base)
Forms carboxylic acid salts (soaps)
Na+ = hard soap; K+ = liquid soap

3. Chemical reactions of TAGs
3. Hydrogenation
Unsaturated chains add H2 (become “hydrogenated”)
Increase the melting point (become semi-solid)
Side effect = production of trans fats

4. Olestra Artificial, noncaloric fat substitute (indigestible)
FDA warning
“This Product Contains Olestra. Olestra may cause abdominal cramping and loose stools. Olestra inhibits the absorption of some vitamins and other nutrients. Vitamins A, D, E, and K have been added.”

5. Reaction map for triglycerides

6. 18.5 Waxes Esters of fatty acids Alcohol has long chain
Insoluble in water
Not easily hydrolyzed
Natural protective coatings on plants, fruit, skin, fur, feathers
Commercially used as candles, cosmetics

7. Membrane/structural lipids
18.6 Phospholipids (phosphoglycerides)
18.7 Sphingolipids (sphingomyelins and glycolipids)

8. 18.8 Biological membranes
Separate contents of cells from external fluids
Semipermeable
Nutrients enter, waste products leave
Lipid bilayer = structural lipids and cholesterol

9. Fluid-mosaic model

10. 18.9 Steroids
Ex: Cholesterol, hormones
4 ring structure

11. Cholesterol Contains –OH Produced by liver Supplied by diet
Precursor for hormones, vitamin D
Component of cell membranes
Provide rigidity
High levels
Gallstones
Deposits on arteries

12. 18.10 Steroid hormones Chemical messengers carried through the blood
Same 4-ring structure as cholesterol
Examples:
Cortisol: increase glucose concentration in the body
Cortisone: anti-inflammatory (arthritis, asthma)
Testosterone, estradiol, estrone, progesterone: sex hormones

13. 18.11 Prostaglandins
Hormones involved in production of pain, fever, inflammatory reactions
Synthesized from arachidonic acid (a polyunsaturated FA)
Synthesis inhibited by NSAIDs
e.g. acetylsalicylic acid (aspirin)

14. Summary of lipids