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Lecture 3: Lipids: Fats, Phospholipids, Steroids

Lecture 3: Lipids: Fats, Phospholipids, Steroids. 1. Yesterday’s Exit Ticket. What element(s) (i.e. atom types) do all 4 molecules have in common? C and H: they are all organic molecules!. 2. Key Themes (2) “ T hink Like a Biologist”: Understand What Life Is .

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Lecture 3: Lipids: Fats, Phospholipids, Steroids

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  1. Lecture 3: Lipids: Fats, Phospholipids, Steroids 1

  2. Yesterday’s Exit Ticket • What element(s) (i.e. atom types) do all 4 molecules have in common? • C and H: they are all organic molecules! 2

  3. Key Themes (2) “Think Like a Biologist”: Understand What Life Is. “Unity” of life: What are the common features of all life? • Structure and function of the molecules of life 3

  4. The Basics: General properties of lipids • Lipids are macromolecules, but technically not polymers No long chains of many repeated subunits 4

  5. We will discuss three lipid classes: Fats Phospholipids Steroids Mostly hydrophobic http://wiki.faithlutheranlv.org/groups/carmanbio/wiki/dbc5b/Lipids.html 5

  6. We will discuss three lipid classes: Fats Phospholipids Steroids Fat = glycerol + 3 fatty acid chains 6

  7. How is a fat constructed? From glycerol + fatty acids Removal of H2O (dehydration synthesis) Fig. 5.11 7

  8. How is a fat constructed? From glycerol + fatty acids Removal of H2O (dehydration synthesis) Fig. 5.11 forms new bond between glycerol & fatty acid Fat with 3 fatty acids = triacylglycerol = triglyceride 8

  9. Fats • Fats are constructed from two types of smaller molecules: glycerol and 3 fatty acids http://www.colorado.edu/ebio/genbio/05_11Fats_A.html (end when box turns orange) 9

  10. Energy storage in fat versus carbohydrate • Carbohydrates = 4 kcal/gram (CHOH)n • Proteins = 4 kcal/gram (CH”R”)n • Fats = 9 kcal/gram(CH2)n I H - C - OH I “Carb” I H - C - H I Fat Gram-for-gram, fats store twice as much energy as carbohydrates and proteins 10

  11. Fat is used to store energy when a compact energy source with minimum weight is needed. What organisms (or stages of organisms) would you predict to store fats (rather than polysaccharides)? 11

  12. Functions of dietary fats • Energy supply (all fats) • Building blocks for body (omega-6 & omega-3 fatty acids needed for brain / heart muscle …) • Diet-gene interaction (omega-6 & omega-3 fatty acids converted to hormone messengers) 12

  13. http://www.colorado.edu/ebio/genbio/05_11Fats_A.html Saturated – single bonds – straight – solid Unsaturated – double bonds – L-shaped – liquid 13

  14. http://spaceflight.esa.int/impress/text/education/Glossary/Glossary_T.htmlhttp://spaceflight.esa.int/impress/text/education/Glossary/Glossary_T.html Which of the fats below (all with the same number of carbon atoms) has the highest energy content? • a fat composed of saturated fatty acids B) a fat composed of monounsaturated fatty acids C) a fat composed of polyunsaturated fatty acids 14 Think-Pair-Share

  15. Saturated and Unsaturated Fats How can you tell them apart? Saturated fats are solid Unsaturated fats are liquid 15

  16. Real World Connection: Saturated and Unsaturated Fats in the News Which is better for your health? Consumption of saturated fats raises cholesterol levels. Most of the cholesterol in human body is synthesizedfrom saturated fats! 16

  17. Stearic acid a) Saturatedfatty acid Oleic acid (b) Monounsaturated fatty acid (MUFA) 17

  18. MUFA Mono Unsaturated Fatty Acid 18 http://wiki.faithlutheranlv.org/groups/carmanbio/wiki/dbc5b/Lipids.html

  19. Recommended changes to current US diet: Reducesaturated fats. Increasemonounsaturated fats. Oleic acid Stearic acid (a) Saturatedfatty acid (b) Monounsaturated fatty acid (MUFA) Fig. 5.12 19

  20. http://instruct.westvalley.edu/svensson/Cells/07molecules.htmhttp://instruct.westvalley.edu/svensson/Cells/07molecules.htm 20

  21. (Note that all PUFAs are highly “kinked”, even though the simple image on the right does not reflect this.) Recommended changes cont: Reduceomega-6 polyunsaturated fatty acids (PUFAs). Increaseomega-3 PUFAs. Difference between Omega-3 and Omega-6 PUFAs http://www.supplementquality.com/news/fatty_acid_structure.html 21

  22. saturated monounsaturated polyunsaturated A saturated fat is saturated with the maximal number of • carbon atoms (C). • hydrogen atoms (H). • C=C bonds. • carbon and hydrogen atoms. • hydrogen atoms and C-H bonds. http://spaceflight.esa.int/impress/text/education/Glossary/Glossary_T.html 22 Think-Pair-Share

  23. http://sabrebrains.blogspot.com/2011/02/lipids.html 23

  24. Predict the result(s) of removing hydrogen atoms from the fatty acid tails of saturated animal fat (lard): A) The number of carbon-carbon double bonds in the fat molecules increases. B) The number of carbon-carbon double bonds in the fat molecules decreases. C) The fat becomes more fluid. D) A and C E) B and C 24 Think-Pair-Share

  25. Latest recommendation for ideal fat composition in the human diet: 70-80% monounsaturated fatty acids 10-15% polyunsaturated fatty acids (omega-6 to omega-3ratio 2:1) 10-15% saturated fatty acids (animal) 25

  26. 10-15% 10-15% 70-80% Ratio of ≤2 to 1 26 http://www.canola-council.org/canola_resources/product45.aspx

  27. Polyunsaturated Fatty Acids (PUFAs) = Essential Fatty Acids (EFAs) Why a 2:1 ratio? Omega-6 Omega-3 Converted to hormones thatslow downcell division and dampen inflammation Converted to hormones thatspeed upcell division and trigger inflammation Healthy, balanced ratio of omega-6 to omega-3 fatty acids is 2:1, whereas estimate formodern US dietis 20:1 =highly unbalanced 27

  28. Polyunsaturated Fatty Acids = Essential Fats Omega-6 Omega-3 (LA, linoleic acid) Lots in corn, sunflower, soybean oil (ALA, alpha-linolenic acid) In flax seed, nuts, canola oil (AA) In meat, milk of grain-fed cattle EPA and DHA In fatty fish Converted to hormones thatspeed upcell division and trigger inflammation Converted to hormones thatslow downcell division and dampen inflammation 28

  29. The Yin & Yang of Inflammation The “GOOD”: Upon injury/infection, pro-inflammatory prostaglandins “call” white blood cells to engulf & destroy injured body cells & invaders. The “BAD”: Overproduction of pro-inflammatory messengers causes white blood cells to attack uninjured body cells. 29 http://taoism.about.com/od/visualsymbols/ig/Taoist-Symbols/Yin-Yang-Symbol.--jj.htm

  30. Impact of dietary fats on human health Chronic disease and disorders Modern western diet Healthful diet Low saturated fat Balanced omega-6:3 fatty acid ratio High saturated fat High omega-6:3 fatty acid ratio PROMOTE PREVENT 30

  31. Just FYI: Real World Advice Good source of omega-3 fatty acids, ± low in mercury & PCBs Stay away from Highly mercury contaminated fish (>1 ppm) Shark Swordfish King mackerel Tilefish And also Bluefin tuna Chilean sea bass Rockfish Grouper Bluefish • Salmon (wild, farmed?) • Mackerel (but not king mackerel!) • Mussels, oysters • Anchovies • Rainbow trout • Herring • Sardines • Tuna (but not bluefin, white/albacore?) 31 http://www.montereybayaquarium.org/cr/cr_seafoodwatch/download.aspx

  32. Which is correct? • omega-3 fatty acids are good and omega-6 fatty acids are bad B) omega-6 fatty acids have no positive effects • both omega-3 fatty acids and omega-6 fatty acids have vital roles in the human body D) the ratio of omega-6 to omega-3 fatty acids is not important for human health E) B, C, and D are all correct 32

  33. 5 minute break 33 blog.famasalescoffee.com

  34. Three types of lipids: Fats Phospholipids Steroids Phospholipid = phosphate + glycerol + 2 fatty acid chains 34

  35. How is a phospholipid constructed? 35 Fig. 5.13

  36. How is a phospholipid constructed? 36 Fig. 5.13

  37. A. B. H20 H20 H20 H20 D. C. H20 H20 H20 H20 A phospholipid is shown below. Predict which of the structures A-D, also shown below, is MOST LIKELY to form when a phospholipid is dispersed in water. hydrophilic (water-loving) polar head group hydrophobic (water-fearing) non-polar tails 37 Think-Pair-Share

  38. Interactions of phospholipid molecules with water The basis of phospholipid bilayers Hydrophilic head WATER Hydrophobic tail Fig. 5.14 WATER 38

  39. Structure-function relationship: Phospholipids are key to the existence of biological cells Hydrophilic head WATER Hydrophobic tail Fig. 5.14 WATER 39

  40. Phospholipid Fat Fig. 5.13 Fig. 5.11 40

  41. (Three types of lipids:) Fats Phospholipids Steroids Steroids = 4 carbon-hydrogen rings 41

  42. http://www.uv.es/EBRIT/macro/macro_5009_2_284.html http://www.sciencephoto.com/media/97627/enlarge 42

  43. Steroids: What are they? 43 pictureschat.com; ellies-whole-grains.com; medicalinsider.com; genesistraining.org.uk

  44. Sex hormones are steroids. Fig. 4.9 Estradiol (an estrogen) Testosterone 44 See pages 977 & 993-994 in textbook for more information

  45. • Has a role in heart disease (will be visited later) Made from saturated dietary fat Fig. 5.15 Cholesterol • Stabilizes biological membranes in animals (will be visited later) 45 • Is an important precursor for other steroids

  46. Roles of cholesterol Fig. 5.15 Precursor in synthesis of: Sex hormones, stress hormones, Vitamin D 46

  47. Synthesis of steroid stress hormones (corticosteroids) from cholesterol 47 http://www.neurosci.pharm.utoledo.edu/MBC3320/steroid_hormones.htm

  48. How does eating NO saturated fats negatively affect your health? It wouldn’t. Saturated fats are bad. It would reduce sex hormones, but who wants to be hormonal anyway? It would reduce steroid hormones, so the body is less muscular. It would reduce sex hormones, and there are negative effects of this. 48

  49. Roles of cholesterol Fig. 5.15 Precursor in synthesis of: Sex hormones, stress hormones, Vitamin D 49

  50. + UV Cholesterol 50 Vitamin D2 http://en.wikipedia.org/wiki/Vitamin_D

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