1. Lipids Why this Chapter?
Lipids are the largest and most diverse class of biomolecules
To examine lipid structure, function, and metabolism

2. About Lipids
Natural materials that preferentially extract into nonpolar organic solvents
Includes fats, oils, waxes, some vitamins and hormones, some components of membrane
General types: esters (“saponifiable”) and those that can’t be hydrolyzed

3. Waxes, Fats, and Oils
Waxes - contain esters formed from long-chain (C16- C36) carboxylic acids and long-chain alcohols (C24-C36)
Triacontyl hexadecanoate is in beeswax

4. Triacylglycerol
Tri-esters of glycerol with three long- chain carboxylic acids, fatty acids.

5. Fatty Acids (from Fats and Oils)
Straight-chain (C12 - C20) carboxylic acids
Double bonds are cis-substituted but trans-fatty acids also occur
A fat or oil in nature occurs as a mixture of many different triacylglycerols
The most abundant saturated fatty acids are palmitic (C16) and stearic (C18)

6. Unsaturated and Polyunsaturated Fatty Acids
Oleic (C18 with one C=C) and linolenic (C18 with 3 C=C) are the most abundant unsaturated

7. Soap
A mixture of sodium or potassium salts of long-chain fatty acids produced by alkaline hydrolysis (saponification) of animal fat with alkali

8. Cleansing Action of Soap
The carboxylate end of the long-chain molecule is ionic and therefore is preferentially dissolved in water
The hydrocarbon tail is nonpolar and dissolves in grease and oil
Soaps enable grease to be dissolved into water

9. Detergents
“Hard” water contains Mg+2 and Ca+2 that form insoluble salts with soaps
Synthetic detergents are alkylbenzene sulfonates that dissolve dirt like soaps but do not form scums with Mg+2 and Ca+2 .

10. Phospholipids Phospholipids are diesters of H3PO4, phosphoric acid
Phosphoric acid can form monoesters, diesters and triesters
In general these are known as “phosphates”

11. Phosphoglycerides
Contain a glycerol backbone linked by ester bonds to two fatty acids and phosphoric acid
Fatty acid residues with C12–C20
The phosphate group at C3 has an ester link to an amino alcohol

12. Sphingolipids The other major group of phospholipids
Sphingosine or a dihydroxyamine backbone
Constituents of plant and animal cell membranes
Abundant in brain and nerve tissue, as coating around nerve fibers.

13. Phosphoglyceride Membranes
Phosphoglycerides comprise the major lipid component of cell membranes
Nonpolar tails aggregate in the center of a bilayer
Ionic head is exposed to solvent

14. Steroids
Steroids,are another class of nonsaponifiable lipid, defined by structure
Has four fused rings A, B, C, and D, beginning at the lower left
Carbon atoms are numbered beginning in the A ring
The six-membered rings are in fixed chair conformations

15. Functions of Steroids
In humans as hormones, steroids are chemical messengers secreted by glands and carried through the bloodstream to target tissues
Also widely distributed as cholesterol

16. Adrenocortical Hormones
Adrenocortical steroids: secreted by the adrenal glands near the upper end of each kidney
Mineralocorticoids: control tissue swelling by regulating cellular salt balance
Glucocorticoids: regulation of glucose metabolism and in the control of inflammation

17. Synthetic Steroids Made in pharmaceutical laboratories as new drugs
Includes oral contraceptives and anabolic agents
Methandrostenolone is an anabolic steroid used for tissue-building