1. Lipids Biochemistry by Reginald Garrett and Charles Grisham
Chapter 8
Lipids
Biochemistry by
Reginald Garrett and Charles Grisham

2. Essential Question
What is the structure, chemistry, and biological function of lipids?
Lipids – low solubility in water and high solubility in nonpolar solvents.
The hydrophobic nature of lipids allows membranes to act as effective barriers to more polar molecules.

3. Outline What Is the Structure and Chemistry of Fatty Acids?
What Is the Structure and Chemistry of Triacylglycerols?
What is the Structure and Chemistry of Glycerophospholipids?
What Are Sphingolipids, and How Are They Important for Higher Animals?
What Are Waxes, and How Are They Used?
What Are Terpenes, and What Is Their Relevance to Biological Systems?
What Are Steriods, and What Are Their Cellular Functions?

4. Classes of Lipids
All biological lipids are amphipathic (containing both polar and nonpolar groups).
Fatty acids
Triacylglycerols
Glycerophospholipids
Sphingolipids
Waxes
Isoprene-based lipids (including steroids)

5. 8.1 - Fatty acids
Know the common names and structures for fatty acids up to 20 carbons long
Saturated
Lauric acid (12 C)
Myristic acid (14 C)
Palmitic acid (16 C)
Stearic acid (18 C)
Arachidic acid (20 C)

6. Fatty acids - II Unsaturated fatty acids Palmitoleic acid (16:1)
Linoleic acid (18:2)
-Linolenic acid (18:3)
-Linolenic acid (18:3)
Arachidonic acid (20:4)

8. Structural consequences of unsaturation
Fatty acids - III
Structural consequences of unsaturation
Saturated chains pack tightly and form more rigid, organized aggregates (i.e., membranes)
Unsaturated chains bend and pack in a less ordered way, with greater potential for motion

9. Fatty acids in Food: saturated vs. unsaturated
Fatty acid compositions of some dietary lipids
Source Lauric
& Myristic Palmitic Stearic Oleic Linoleic
Beef
Milk
Coconut
Corn
Olive
Palm
Safflower
Soybean
Sunflower

10. Also called triglycerides
8.2 - Triacylglycerols
Also called triglycerides
A major energy source for many organisms
Why?
Most reduced form of carbon in nature
No solvation needed
Efficient packing

11. Triacylglycerols - II
Other advantages accrue to users of triacylglycerols :
Insulation
Energy without nitrogen
Metabolic water

12. 8.3 - Glycerophospholipids
Glycerophospholipids are phospholipids but not necessarily vice versa.
Know the names and structures in Figure 8.6
Understand the prochirality of glycerol
Remember that, if phospholipid contains unsaturation, it is at the 2-position.

14. Ether Glycerophospholipids
An ether instead of an acyl group at C-1
Figure 8.8
1-alkyl 2-acyl-phosphatidylethanolamine
(an ether glycerophospholipid)

15. Ether Glycerophospholipids
Platelet activating factor (PAF) is an ether glycerophospholipid.
PAF is a potent biochemical signal molecule
Note the short (acetate) fatty acyl chain at the C-2 position in PAF.
PAF is much more water soluble, functions as a soluble messenger in signal transduction.
Figure alkyl 2-acyl-phosphatidylcholine
(PAF)

16. Base structure is sphingosine.
8.4 – Sphingolipids 神經鞘脂質
Base structure is sphingosine.
Sphingosine is an 18-carbon amino alcohol.
Ceramides are amide linkages of fatty acids to the nitrogen of sphingosine.
Glycosphingolipids are ceramides with one or more sugars in beta-glycosidic linkage at the 1-hydroxyl group.

17. Base structure is sphingosine.
Sphingolipids
Base structure is sphingosine.
Sphingosine is an 18-carbon amino alcohol.
Ceramides (神經醯胺) are amide linkages of fatty acids to the nitrogen of sphingosine.
Glycosphingolipids are ceramides with one or more sugars in beta-glycosidic linkage at the 1-hydroxyl group.
Figure 8.11  Formation of an amide linkage between a fatty acid and sphingosine produces a ceramide.

18. Sphingolipids
Backbone of sphingosine: 18-carbon amino alcohol with C-C trans double bond
 Ceramide: sphingosine with fatty acid in amide linkage
 Sphingomyelins: alcohol esterified to phosphoceramide
Choline
Ethanolamine
Glycosphingolipids: ceramide with sugars in -glycosidic linkage
Cerebroside: Sugar is glucose or galactose.
Sulfatide: Sugar is galactose with sulfate esterified at carbon 3 of galactose.
Gangliosides: ceramide with three or more sugars
including sialic acid

19. Esters of long-chain alcohols with long-chain fatty acids
8.5 - Waxes
Esters of long-chain alcohols with long-chain fatty acids
Highly insoluble
Animal skin and fur are wax-coated
Leaves of many plants
Bird feathers

20. Esters of long-chain alcohols with long-chain fatty acids
8.5 Waxes
Esters of long-chain alcohols with long-chain fatty acids
highly insoluble
Animal skin and fur are
wax-coated .
leaves of many plants
bird feathers
Figure 8.15 An example of a wax. Oleoyl alcohol is esterified to stearic acid in this case.

21. Based on the isoprene structure
8.6 - Terpenes
Based on the isoprene structure
Know nomenclature
Understand linkage modes (Figure 8.16)
See structures in Figure 8.17
All sterols (including cholesterol) are terpene-based molecules.
Steroid hormones are terpene-based.

22. Based on the isoprene structure
8.6 Terpenes
Based on the isoprene structure
Know nomenclature
All sterols (including cholesterol) are terpene-based molecules.
Steroid hormones are terpene-based.
Figure 8.16

23. 8.7 - Steroids
Based on a core structure consisting of three 6-membered rings and one 5-membered ring, all fused together.
Cholesterol is the most common steroid in animals and precursor for all other steroids in animals.
Steroid hormones serve many functions in animals - including salt balance, metabolic function and sexual function.

24. An A-B cis steroid

25. Figure 8.19 The structure of cholesterol, shown with steroid ring designations and carbon numbering.