1. Lipids
Lipids: a heterogeneous class of naturally occurring organic compounds (mainly esters) classified together on the basis of common solubility properties

2. Lipids Lipids include ESTERS
Triacylglycerols (triglycerides), phosphoacylglycerols (phospholipids), sphingolipids, glycolipids.
NON-ESTERS
cholesterol, steroid hormones, and bile acids
lipid-soluble vitamins, and prostaglandins

8. Waxes Waxes are very water insoluble and high melting point.
They are widely distributed in nature as protective waterproof coatings on leaves, fruits, animal skin, fur, feathers and exoskeletons
Prentice Hall c2002
Chapter 9

9. Waxes
Esters of long-chain fatty acids and long chain monohydroxylic alcohols
from the Old English word weax = honeycomb

10. Triacylglycerols Esters of glycerol with three fatty acids
Fatty acids are stored as neutral lipids, triaclyglycerols (TGs)
TGs are hydrophobic, stored in fat cells (adipocytes)
Structure of a triacylglycerol
Prentice Hall c2002
Chapter 9

11. Glycerophospholipids

12. Glycerophospholipids

13. Structures of glycerophospholipids
Phosphatidylcholine (PC)
Prentice Hall c2002
Chapter 9

14. Structures of glycerophospholipids

15. Structures of glycerophospholipids
Phosphatidylserine (PS)
Prentice Hall c2002
Chapter 9

16. Cardiolipin:
Two molecules of PA esterified through their phosphate groups to an additional molecule of glycerol is called cardiolipin

17. Importance of cardiolipin
Cardiolipin is found in bacteria and eukaryotes (inner mitochondrial membrane)
Cardiolipin is antigenic, and is recognized by antibodies raised against Treponema pallidum, the bacterium that causes syphilis

18. Sphingolipids
Sphingolipids - sphingosine is the backbone. Abundant in central nervous system tissues
Ceramides - fatty acyl group linked to sphingosine
Sphingomyelins - phosphocholine attached to ceramide
Cerebrosides - glycosphingolipids with one monosaccharide residue attached to ceramide
Galactosylcerebrosides - a single b-D-galactose as a polar head group
Gangliosides - contain oligosaccharide chains with N-acetyl-neuraminic acid (NeuNAc) attached to a ceramide
Prentice Hall c2002
Chapter 9

19. Sphingosine (b) Ceramides
Prentice Hall c2002
Chapter 9

20. Significance of Ceramide & sphingosine
A long-chain fatty acid is attached to the amino group of sphingosine through an amide linkage
Ceramides appear to be involved in the response to stress
sphingosine inhibits protein kinase C

22. Sphingomyelin Amino alcohol sphingosine, rather than glycerol
The alcohol group at carbon 1 of sphingosine is esterified to phosphorylcholine
Sphingomyelin is an important constituent of the myelin of nerve fibers

23. Sphingomyelin degradation
Sphingomyelin is degraded in lysosomes by sphingomyelinase to give ceramide,
and ceramidase to give sphingosine
Niemann-Pick disease is due to sphingomyelinase deficiency

24. Glycolipids Also known as glycosphingolipids
contain both carbohydrate and lipid components
Ceramides plus a long-chain fatty acid attached to the amino alcohol sphingosine
essential components of:
All membranes
Nerve cells

25. Glycolipids Significance
Glycosphingolipids are antigenic  a source of blood group antigens
The carbohydrate portion of a glycolipid is the antigenic determinant
serve as cell surface receptors for cholera and tetanus toxins

26. Galactocerebroside—the most common cerebroside found in membranes
Structure of a galactocerebroside
Galactocerebroside—the most common cerebroside found in membranes
Glucocerebroside
Prentice Hall c2002
Chapter 9

27. Location
cerebrosides predominantly in the brain and peripheral nervous tissue

28. Ganglioside (sphingolipid)
found in the ganglion cells
Derivatives of ceramide oligosaccharides, and contain one or more molecules of NANA.
negatively charged at physiologic pH  provided by N-acetylneuraminic acid (NANA).
[NANA is also referred to as sialic acid.]