Lipids: Structure, Functions, and Metabolism

1. Midterm –as per course syllabus Fibre and irritable bowel syndrome https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5467063/ https://www.npjournal.org/article/S1555-4155(15)01191-5/pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3272664 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5548066/

2. Carbohydrate/lipid/protein/alcohol 4/9/4/7 kcal/gram 17/37/17/29 kJ/gram Note alcohol = ethanol

3. The new normal-Globe and Mail- 30 September 2012- parents do not recognise when they and/or others including kid(s) is/are overweight or obese Fat is the new normal

4. Lecture 5a 7 Oct. 2019 Lipids I 94/80

10. Overview of lecture 5a 1) Lipids defined 2) Functions of fats in foods 3) Structure, classification, presence in food and function of: a) fatty acids b) triglycerides c) phospholipids d) cholesterol 4) Ingestion, digestion, absorption, transport, metabolism and excretion 6) Functions of lipids-essential or not

11. Lipids defined family of compounds that includes triglycerides, (TG), phospholipids (PL) and sterols other definition water insoluble organic compounds made up of C, H, and O like carbohydrates but less O and therefore 9 vs 4 kcal/gm

12. 2)Functions of fats in foods • absorbing flavours and aromas of ingredients • providing flavour of its own • creamy and smooth mouth taste • tenderizing and adding moisture

13. a)Triglycerides-fatty acids-structure, classification Organic acid Saturated 14:0 Monounsaturated 18:1 Polyunsaturated 18:2 n-6 18:3 n-6 (gamma-linolenic acid) 18:3 n-3 (alpha-linolenic acid)

14. REPLACE WITH FIG 5-2 ACETIC ACID Fig. 5-1, p. 140

15. p. 134

16. p. 134

17. p. 135

18. p. 135

19. p. 135

20. p. 135

22. a)Triglycerides-fatty acids-structure, classification Glycerol + 3 fatty acids make a triglyceride Mixed triglycerides

25. Fig. 5-4, p. 137

26. Triglycerides continued Triglycerides infood Processed fat-fat manipulated mechanically or chemically -chemical manipulation-hydrogenation- -hydrogenation yields trans-fatty acids

27. Fig. 5-7, p. 138

28. Fig. 5-8, p. 139

29. A)- Triglycerides- in foods and function In foods-triglycerides are most of the fat in our foods (followed by sterols followed by phospholipids) Function in our bodies-triglycerides are an energy source and a major storage form of energy in our bodies

30. B) Phospholipids- structure, classification, in foods and function Structure- 2 FATTY ACIDS (FA) and polar head group-generally but exceptions Classification Choline-containing phospholipids Ethanolamine-containing phospholipids Phosphatidylserine Phospatidylinositol Sphingomyelin

31. Fig. 5-9, p. 140

32. Phospholipids continued Foods- found naturally Function p. 140 Membranes Lipoproteins Cell signalling

33. C) Sterols- structure, classification, in foods and function Structure-Ring structure Classification-Sterols

34. Fig. 5-11, p. 141

35. Sterols continued Foods- found naturally-cholesterol vs phytosterol Function Membranes Lipoproteins Bile acids Hormones Vitamin D

38. Fatty acids in foods regardless of free or esterified Function of fatty acids in food essential in diet- linoleic acid and alpha-linolenic acid-we cannot make these

39. Ingestion- mouth, tube or IV Digestion of lipids fats start out separated from enzymes in gi (gastrointestinal tract)-why?\ goal of fat digestion mouth digestion of fat small intestine digestion of fat

40. Absorption of lipids small molecules short chain fatty acids medium chain fatty acids glycerol direct to blood larger molecules monoglycerides long chain fatty acids micelles formed in intestine micelles into intestinal wall cells chylomicrons formed and released into lymph http://wowzahttp.cengage.com/digital-production/nutrition/Digestion_and_Absorption_of_Lipids.mp4

41. Transport of lipids Lipoproteins-chylomicrons (CM) (POST-PRANDIAL ONLY) - very low density lipoprotein (VLDL) - low density lipoprotein (LDL) - high density lipoprotein (HDL) - albumin density change due to 2 factors

42. Lipoprotein metabolism Chylomicrons- made in small intestine – acted on by lipoprotein lipase in blood to give remnant particle which is taken up liver VLDL (very low density lipoprotein) made via liver VLDL acted on by lipoprotein lipase in blood to give remnant particle (intermediate density lipoprotein or IDL) which is taken up by liver- liver puts out low density lipoprotein (LDL) HDL ( high density lipoprotein) and albumin made by liver

43. Human lipid metabolism-in part only Fatty acids oxidised in mitochondria to give energy and water Glycerol metabolised (enters glycolytic path and then mitochondria) Can also synthesise fatty acids, triglycerides, phospholipids and sterols

44. Lipids excretion Faeces-undigested and/or unabsorbed fat Respiration (lipid metabolites -water and CO2) Urine-lipid metabolite (water) Sweat-lipid metabolite (water) Saliva?-intact fats and lipid metabolite (water)

45. Lipids essential or not ? Yes-why ? healthy roles

46. Lipids- essential or not? yes- healthy roles 1)insulation- healthy roles protective layer in body to help keep heat losses down

47. Lipids-essential or not? yes Healthy roles 2)support and protection for internal organs and bones fat acts as support and cushioning for organs and cushioning for bones

48. Lipids- essential or not? yes Healthy roles 3)absorption of fat soluble vitamins fat soluble vitamins cannot be absorbed without fat in the diet- why?

49. Lipids- essential or not? yes Healthy roles 4)cell membranes cholesterol and phospholipids are important in maintaining the structure and hence function of cell membranes what is a cell membrane?

50. Lipids- essential or not? yes Healthy roles 5) gives structure to molecules fatty acids give rise to triglycerides and phospholipids and cholesterol fatty acid complexes structure of lipids in part dictates their function