1. Oils and fats

2. The definition of a lipid The definition of a lipid is based on solubility --- marginally soluble in water and soluble in organic solvents Classification: Group I: open-chain compounds with polar head groups and long nonpolar tails fatty acids triacylglycerols waxes sphingolipids phosphoacylglycerols glycolipids Group II: fused-ring compounds (steroids)

3. The chemical natures of the lipid types Fatty acids (1) Amphipathic (2) Unstaurated vs. saturated (3) Different melting points (4) Rarely found free in nature trans vs. cis

4. Fatty acids (1) Amphipathic (2) Unstaurated vs. saturated (3) Different melting points (4) Rarely found free in nature

5. Triacylglycerols (1)Formed from glycerol and fatty acids (2)Not as components in membrane, but accumulate in adipocytes as stores of metabolic energy

7. Phosphoacylglycerols --- (1) important components in membrane (2) amphipathic

8. Structures of some phosphoacylglycerols PE PC PS PI

9. Structures of some waxes and sphingolipids Abundant in the nervous system Wax from whales

10. Glycolipid (1) Often found as markers on cell membranes (2) Important in tissue and organ specificity (3) Abundant in the nervous system

11. Structures of several important gangliosides

12. Structures of some steroids (1)Cholesterol is widespread in biological membranes, but not in prokaryotic cell membranes

13. The nature of biological membranes (1)Made up by lipids and proteins (2)Separate cells from the external environment (3)Transport of specific substances into/out of cells (4)Enzymes in membranes with specific functions

14. Lipid bilayers

15. Lipid bilayer asymmetry

16. Effects of unsaturated side chains on the packing of the phospholipids

17. Stiffening of the lipid bilayer by cholesterol

18. Effect of temperature on the fluidity of lipid bilayer Flip-flop migration of lipid molecules

19. Membrane Proteins Peripheral protein Integral protein

20. Lipid anchors Glycine residue Cysteine residue

21. Fluid mosaic model of membrane structure

22. Membrane structure revealed by freeze-fractured technique

23. Electron micrograph of a freeze-fractured membrane

24. Membrane Function Membrane transport (1)Passive transport (a) simple diffusion (b) facilitated diffusion (2) Active transport (a) primary active transport (b) secondary active transport

25. Glucose transport

26. The sodium-potassium pump Primary active transport

28. Secondary active transport Galactoside permease high low high

29. Membrane Receptors Low-density lipoprotein (LDL) – principle carrier of cholesterol

30. Lipid-soluble vitamins

31. Reaction of vitamin A

32. The formation of rhodopsin from 11-cis-retinal and opsin

33. Anti-oxidant --- free radicals

34. Reaction of vitamin D

35. Vitamin K

36. Role of vitamin K in blood clotting

37. Postaglandins and Leukotrienes Postaglandins (1)produced by prostate gland (2)synthesized from arachidonic acid (3)control of blood pressure, stimulation of smooth muscle contraction induction of inflammation (4)aspirin, cortisone

38. Leukotrienes (1)formed in leukocytes (white blood cells) (2)synthesized from arachidonic acid (3)stimulation of smooth muscle constriction especially in the lungs (Asthma) COOH H 2 C CH COO- S + NH 3 Triene Cysteine