1. Lipids Los Altos High School Mr. Free Fall 2014 1

2. 2 Triglycerides TriglyceridesTriglycerides are a storage form of fatty acids in mammals. Triglycerides Often when blood tests are done, they measure your triglycyeride levels. Often when blood tests are done, they measure your triglycyeride levels. High triglyceride levels in the blood are a risk indicator for artherosclerosis. High triglyceride levels in the blood are a risk indicator for artherosclerosis. artherosclerosis *American Heart Association American Heart AssociationAmerican Heart Association *American Heart Association American Heart AssociationAmerican Heart Association

3. 3 Triglycerides Triglycerides are a combination of three 3 fatty acid molecules with a glycerol molecule.

4. 4 Triglycerides GlycerolGlycerol, which is also called glycerin, is an alcohol with three hydroxyl groups. Glycerol As with the waxes, the fatty acids can react with the hydroxyl groups to form esters. As with the waxes, the fatty acids can react with the hydroxyl groups to form esters. Since there are three hydroxyl groups, three fatty acids can react to form three esters. Since there are three hydroxyl groups, three fatty acids can react to form three esters.

5. 5 Triglycerides For triglycerides, all three hydroxyls of the glycerol have a fatty acid residue attached to it.

6. 6 Figure 8.6 fromRaymond fromRaymond

7. 7 Triglycerides Just as with fatty acids, where the presence of cis double bonds lower the melting points, triglycerides made from unsaturated fatty acids have lower melting points than those made from saturated fatty acids. Triglycerides from animals tend to have a higher proportion of saturated fatty acids. Triglycerides from animals tend to have a higher proportion of saturated fatty acids. Most are solids at room temperature and are called fats. Most are solids at room temperature and are called fats. Examples include: butter, lard and bacon grease Examples include: butter, lard and bacon grease Triglycerides from plants tend to have a higher proportion of unsaturated fatty acids. Triglycerides from plants tend to have a higher proportion of unsaturated fatty acids. Most are liquids at room temperature and are called oils. Most are liquids at room temperature and are called oils. Examples include: corn oil, canola oil, peanut oil and olive oil. Examples include: corn oil, canola oil, peanut oil and olive oil.

8. 8 Triglycerides Triglycerides as primarily used as a form of stored energy. This is why when you eat more than you need to meet your energy requirements, the excess energy is stored in the form of fat. This is why when you eat more than you need to meet your energy requirements, the excess energy is stored in the form of fat. Fat can store almost twice as much energy per gram as carbohydrates and proteins Fat can store almost twice as much energy per gram as carbohydrates and proteins In mammals the fats are stored in the adipose tissue. In mammals the fats are stored in the adipose tissue.adipose tissueadipose tissue Adipose tissue also functions to protect organs from shock and cold. Adipose tissue also functions to protect organs from shock and cold.

9. 9 Triglycerides Reactions that involve triglycerides include: Hydrogenation Hydrogenation Oxidation Oxidation Base-catalyzed hydrolysis (saponification) Base-catalyzed hydrolysis (saponification)

10. 10 Transport of fats: Dietary fat LDL transfers cholesterol to tissues from liver. VLDL moves triglycerides from liver to tissues. HDL carries cholesterol from tissues to liver. Monoglycerides and fatty acids are absorbed by intestines - transported as chylomicrons in lymph system to blood.-Fat Blocker-Xenical (Alli)Xenical (Alli)

11. 11 Triglycerides Hydrogenation of triglycerides This is the same reaction that we saw in Unit 4 with the hydrogenation of alkenes. This is the same reaction that we saw in Unit 4 with the hydrogenation of alkenes. Unsaturated fats and oils contain alkenes and can be hydrogenated to produce saturated fats. Unsaturated fats and oils contain alkenes and can be hydrogenated to produce saturated fats. Commercially, vegetable oils are often hydrogenated to produce a solid product that has better qualities for making baked goods. Commercially, vegetable oils are often hydrogenated to produce a solid product that has better qualities for making baked goods. ‣ Animal fats, such as butter and lard, which are naturally saturated, can also be used, but unlike the vegetable oils, they come with cholesterol, which is undesirable for health reasons.

12. 12 Triglycerides Hydrogenation of triglycerides This is the same reaction that we saw in Unit 4 with the hydrogenation of alkenes. This is the same reaction that we saw in Unit 4 with the hydrogenation of alkenes. Unsaturated fats and oils contain alkenes and can be hydrogenated to produce saturated fats. Unsaturated fats and oils contain alkenes and can be hydrogenated to produce saturated fats. Commercially, vegetable oils are often hydrogenated to produce a solid product that has better qualities for making baked goods. Commercially, vegetable oils are often hydrogenated to produce a solid product that has better qualities for making baked goods. Animal fats, such as butter and lard, which are naturally saturated, can also be used in baking, but unlike the vegetable oils, they come with cholesterol, which is undesirable for health reasons. Animal fats, such as butter and lard, which are naturally saturated, can also be used in baking, but unlike the vegetable oils, they come with cholesterol, which is undesirable for health reasons.

13. 13 Triglycerides Hydrogenation of triglycerides Total hydrogenation Total hydrogenation liquidliquidsolidsolid

14. 14 Triglycerides Hydrogenation of triglycerides Partial hydrogenation Partial hydrogenation liquidliquidsolidsolid

15. 15 Triglycerides Hydrogenation of triglycerides Partial hydrogenation cab produce trans fats. Partial hydrogenation cab produce trans fats. Trans fats have been found to lower your HDL (“Good cholesterol”) levels. Trans fats have been found to lower your HDL (“Good cholesterol”) levels.

16. 16 Triglycerides Saturated vs Unsaturated Fats

17. 17 Triglycerides Saturated vs Unsaturated Fats

18. 18 Triglycerides Saturated vs Unsaturated Fats

19. 19 Triglycerides Saturated vs Unsaturated Fats

20. 20 Triglycerides Saturated vs Unsaturated Fats Fat (Triacylglyceride)

21. 21 Triglycerides Oxidation of triglycerides Unsaturated triglycerides can react with oxygen to produce small change fatty acids another small molecules. Unsaturated triglycerides can react with oxygen to produce small change fatty acids another small molecules. These often do not smell very good These often do not smell very good This is what happens when butter goes rancid. This is what happens when butter goes rancid. This makes solid fats and oils more stable than liquid oils and is why the solid fats are preferred for deep frying. This makes solid fats and oils more stable than liquid oils and is why the solid fats are preferred for deep frying.

22. 22 Triglycerides Saponification of triglycerides Saponification is the base-catalyzed hydrolysis of the ester bonds in a triglyceride. Saponification is the base-catalyzed hydrolysis of the ester bonds in a triglyceride. This cleaves the esters back into carboxylic acids (fatty acids) and an alcohol (glycerol). This cleaves the esters back into carboxylic acids (fatty acids) and an alcohol (glycerol). Because the reaction is base-catalyzed, the base also reacts with the carboxylic acids to from carboxylate ions Because the reaction is base-catalyzed, the base also reacts with the carboxylic acids to from carboxylate ions We saw this on an earlier slide We saw this on an earlier slideearlier slideearlier slide

23. 23 Reactions With Water Hydrolysis example: The base catalyzed hydrolysis of fats produces soap and glycerol The base catalyzed hydrolysis of fats produces soap and glycerol FatFat

24. 24 Reactions With Water Hydrolysis example: The base catalyzed hydrolysis of fats produces soap and glycerol The base catalyzed hydrolysis of fats produces soap and glycerol SoapSoapGlycerolGlycerol

25. 25 Phospholipids and Glycolipids Phospholipids and Glycolipids are the stuff that biological membranes are made of. Like the soaps, these molecules are highly aphipathic, and when mixed with water spontaneously form membranes that are described as lipid bilayers. Like the soaps, these molecules are highly aphipathic, and when mixed with water spontaneously form membranes that are described as lipid bilayers.lipid bilayerslipid bilayers

26. 26 Phospholipids and Glycolipids Soaps form Micelles Micelles Phospholipids form Lipid Bilayers Phospholipids form Lipid Bilayers

27. 27 Phospholipids and Glycolipids Phospholipids and Glycolipids are the stuff that biological membranes are made of. Like the soaps, these molecules are highly aphipathic, and when mixed with water spontaneously form membranes that are described as lipid bilayers. Like the soaps, these molecules are highly aphipathic, and when mixed with water spontaneously form membranes that are described as lipid bilayers.lipid bilayerslipid bilayers

28. 28 Phospholipids and Glycolipids Phosphospholipids There a are two types of phospholipids There a are two types of phospholipids Glycerophospholipids Glycerophospholipids

29. 29 Phospholipids and Glycolipids Phosphospholipids There a are two types of phospholipids There a are two types of phospholipids Sphingolipids Sphingolipids

30. 30 Phospholipids and Glycolipids Phosphospholipids The Glycerophospholipids have a structure similar to triglycerides, with one of the fatty acids replaced with a phosphate. The Glycerophospholipids have a structure similar to triglycerides, with one of the fatty acids replaced with a phosphate. There is usually an additional alcohol attached to the other side of the phosphate

31. 31 Phospholipids and Glycolipids Phosphospholipids The Glycerophospholipids have a structure similar to triglycerides, with one of the fatty acids replaced with a phosphate. The Glycerophospholipids have a structure similar to triglycerides, with one of the fatty acids replaced with a phosphate. phosphoesterbondsphosphoesterbonds

32. 32 Phospholipids and Glycolipids Phosphospholipids The Glycerophospholipids have a structure similar to triglycerides, with one of the fatty acids replaced with a phosphate. The Glycerophospholipids have a structure similar to triglycerides, with one of the fatty acids replaced with a phosphate. “Phosphotidyl-” refers to everything but the X “Phosphotidyl-” refers to everything but the X

33. 33 Phospholipids and Glycolipids Phosphospholipids Phospholipids are used commercially as emulsifying agents. Phospholipids are used commercially as emulsifying agents. An emulsifying agent stabilizes an emulsion. An emulsifying agent stabilizes an emulsion. An emulsion is a colloidal suspension of one liquid in another. An emulsion is a colloidal suspension of one liquid in another. ‣ An example is mayonnaise, which is a colloidal suspension of oil and water. Lecithin, which is another name for the phospholipid phosphotidylcholine, is used as an emulsifying agent in mayonnaise and other prepared foods. Lecithin, which is another name for the phospholipid phosphotidylcholine, is used as an emulsifying agent in mayonnaise and other prepared foods. Lecithin

34. 34 Phospholipids and Glycolipids Phosphospholipids The sphingolipids function similarly to the glycerophospholipids, but structurally they are different. The sphingolipids function similarly to the glycerophospholipids, but structurally they are different. There is not glycerol core There is not glycerol core The glycerol and one of the fatty acids found in glycerophospholipids is replaced with a molecule called sphingosine. The glycerol and one of the fatty acids found in glycerophospholipids is replaced with a molecule called sphingosine.

35. 35 Phospholipids and Glycolipids Phosphospholipids The sphingolipids are found in the myelin membranes that insulate the nerve cells. The sphingolipids are found in the myelin membranes that insulate the nerve cells. Some sphingolipids use sugars for the alcohol portion of the molecule Some sphingolipids use sugars for the alcohol portion of the molecule These are called glycolipids. These are called glycolipids.

36. 36 Steroids Steroids are a type of lipid that is not derived form a fatty acid. They are based instead on a system of five cycloalkane rings that are fused together. They are based instead on a system of five cycloalkane rings that are fused together.

37. 37 Steroids Steroids are a type of lipid that is not derived form a fatty acid. They are based instead on a system of five cycloalkane rings that are fused together. They are based instead on a system of five cycloalkane rings that are fused together.

38. 38 Steroids Cholesterol is the steroid that used as the starting point for the synthesis of other steroids. Note the fused ring system

39. 39 Steroids Cholesterol is only found in animals Cholesterol is only found in animals Besides being used to synthesize the other steroids, cholesterol is dissolved in membranes to keep them fluid. Besides being used to synthesize the other steroids, cholesterol is dissolved in membranes to keep them fluid. Plants use the alternative strategy of using polyunsaturated fatty acids to make their phospholipids. Plants use the alternative strategy of using polyunsaturated fatty acids to make their phospholipids.

40. 40 Lipoproteins Lipoproteins are used to transport the water insoluble lipids such as triglycerides, phospholipids and cholesterol, in the blood. Lipoproteins contain lipids and proteins. Lipoproteins contain lipids and proteins. They include: They include: Chylomicrons transport primarily triglycerides from the digestive track. Chylomicrons transport primarily triglycerides from the digestive track. LDLs (low density lipoproteins) transport cholesterol, triglycerides and phospholipids from the liver to other tissues. LDLs (low density lipoproteins) transport cholesterol, triglycerides and phospholipids from the liver to other tissues. HDLs (high density lipoproteins) transport cholesterol and phospholipids back to the liver. HDLs (high density lipoproteins) transport cholesterol and phospholipids back to the liver.

41. 41 Lipoproteins The HDL and LDL levels in the blood can be used to assess ones risk for atherosclerosis. High levels of HDL is considered good High levels of HDL is considered good This is why HDL is sometimes referred to as “good cholesterol” This is why HDL is sometimes referred to as “good cholesterol” > 40 mg/dL is good. > 40 mg/dL is good. High levels of LDL is considered bad High levels of LDL is considered bad This is why LDL is sometimes referred to as “bad cholesterol” This is why LDL is sometimes referred to as “bad cholesterol” > 100 mg/dL is bad. > 100 mg/dL is bad.

42. 42

43. 43 Eicosanoids Eicosanoids are derived from arachidonic acid:

44. 44 Membranes Fluid mosaic model

45. 45 Membranes Transport across membranes

46. The End